Improvement output for ".schema --indent" in the CLI when the schema contains

partial indexes with long and complicated WHERE clauses. FossilOrigin-Name: 94c6e8d97158fde5c8200206cf21e8acc9de8d1b4cbaf7db8d9c6a56ad6762e4
Update Lemon so that it accepts filename arguments to directives like
2025-03-05 16:30:36 +00:00 · 2025-03-05 13:39:33 +00:00 · 2025-03-04 17:06:38 +00:00 · 2025-03-03 16:53:48 +00:00 · 2025-02-18 14:56:13 +00:00 · 2025-02-06 12:56:07 +00:00
62 changed files with 3953 additions and 562 deletions
@@ -1616,6 +1616,7 @@ TESTSRC = \
  $(TOP)\src\test_quota.c \
  $(TOP)\src\test_rtree.c \
  $(TOP)\src\test_schema.c \
+  $(TOP)\src\test_schemapool.c \
  $(TOP)\src\test_superlock.c \
  $(TOP)\src\test_syscall.c \
  $(TOP)\src\test_tclsh.c \
@@ -725,6 +725,10 @@ as part of the output file.</p>
 <p>There can be multiple <tt>%code</tt> directives.  The arguments of
 all <tt>%code</tt> directives are concatenated.</p>

+<p>If the argument to <tt>%code</tt> is a filename within <tt>&lt;...&gt;</tt>
+then the content of the named file is inserted instead of the text of the
+argument itself.
+
 <a id='default_destructor'></a>
 <h4>4.4.2 The <tt>%default_destructor</tt> directive</h4>

@@ -920,6 +924,11 @@ For example:</p>
 <p>This might be needed, for example, if some of the C actions in the
 grammar call functions that are prototyped in unistd.h.</p>

+<p>If the argument to <tt>%include</tt> is a filename within
+<tt>&lt;...&gt;</tt> then the content of that file is inserted instead
+of the text of the argument itself.
+
+
 <p>Use the <tt><a href="#pcode">%code</a></tt> directive to add code to
 the end of the generated parser.</p>

@@ -0,0 +1,142 @@
+
+Shared-Schema Mode Notes
+========================
+
+The [reuse-schema](/timeline?r=reuse-schema) branch contains changes 
+to allow SQLite connections to share schemas
+between database connections within the same process in order to save memory.
+Schemas may be shared between multiple databases attached to the same or
+distinct connection handles.
+
+Compile with -DSQLITE\_ENABLE\_SHARED\_SCHEMA in order to enable the
+shared-schema enhancement.  Enabling the shared-schema enhancement causes
+approximately a 0.1% increase in CPU cycles consumed and about a 3000-byte
+increase in the size of the library, even if shared-schema is never used.
+
+Assuming the compile-time requirements are satisfied, the shared-schema
+feature is engaged by opening the database connection using the
+sqlite3&#95;open&#95;v2() API with the SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA
+flag specified.  The main database and any attached databases will then share
+an in-memory Schema object with any other database opened within the process
+for which: 
+
+  * the contents of the sqlite&#95;master table, including all object names,
+    SQL statements and root pages are identical, and
+  * have the same values for the schema-cookie.
+
+Temp databases (those populated with "CREATE TEMP TABLE" and similar
+statements) never share schemas.
+
+Connections opened with the SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA flag
+specified may not modify any database schema except that belonging to the
+temp database in anyway. This includes creating or dropping database 
+objects, vacuuming the database, or running ANALYZE when the
+sqlite&#95;stat\[14\] tables do not exist.
+
+For SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA connections, the
+SQLITE&#95;DBSTATUS&#95;SCHEMA&#95;USED sqlite3&#95;db&#95;status() verb
+distributes the memory used for a shared schema object evenly between all
+database connections that share it.
+
+## The ".shared-schema" Command
+
+The shell tool on this branch contains a special dot-command to help with
+managing databases. The ".shared-schema" dot-command can be used to test
+whether or not two databases are similar enough to share in-memory schemas,
+and to fix minor problems that prevent them from doing so. To test if
+two or more database are compatible, one database is opened directly using 
+the shell tool and the following command issued:
+
+        .shared-schema check <database-1> [<database-2>]...
+
+where &lt;database-1&gt; etc. are replaced with the names of database files
+on disk. For each database specified on the command line, a single line of
+output is produced. If the database can share an in-memory schema with the
+main database opened by the shell tool, the output is of the form:
+
+        <database> is compatible
+
+Otherwise, if the database cannot share a schema with the main db, the output
+is of the form:
+
+        <database> is NOT compatible (<reason>)
+
+where &lt;reason&gt; indicates the cause of the incompatibility. &lt;reason&gt;
+is always one of the following.
+
+<ul>
+  <li> <b>objects</b> - the databases contain a different set schema objects
+  (tables, indexes, views and triggers).
+
+  <li> <b>SQL</b> - the databases contain the same set of objects, but the SQL
+  statements used to create them were not the same.
+
+  <li> <b>root pages</b> - the databases contain the same set of objects created
+  by the same SQL statements, but the root pages are not the same.
+
+  <li> <b>order of sqlite&#95;master rows</b> - the databases contain the same
+  set of objects created by the same SQL statements with the same root pages,
+  but the order of the rows in the sqlite&#95;master tables are different.
+
+  <li> <b>schema cookie</b> - the database schemas are compatible, but the 
+  schema cookie values ("PRAGMA schema&#95;version") are different.
+</ul>
+
+The final three problems in the list above can be fixed using the
+.shared-schema command. To modify such a database so that it can share a 
+schema with the main database, the following shell command is used:
+
+        .shared-schema fix <database-1> [<database-2>]...
+
+If a database can be modified so that it may share a schema with the main
+database opened by the shell tool, output is as follows:
+
+        Fixing <database>... <database> is compatible
+
+If a database does not require modification, or cannot be modified such that
+it can share a schema with the main database, the output of "fix" is identical
+to that of the "check" command.
+
+## Implementation Notes
+
+A single Schema object is never used by more than one database simultaneously,
+regardless of whether or not those databases are attached to the same or
+different database handles. Instead, a pool of schema objects is maintained 
+for each unique sqlite&#95;master-contents/schema-cookie combination
+opened within the process. Each time database schemas are required by a
+connection, for example as part of an sqlite3&#95;prepare\*(),
+sqlite3&#95;blob&#95;open() or sqlite3&#95;blob&#95;open() call, it obtains
+the minimum number of schemas required from the various schema-pools, returning
+them at the end of the call. This means that a single schema-pool only ever
+contains more than one copy of the schema if:
+
+  * Two threads require schemas from the same pool at the same time, or
+  * A single sqlite3&#95;prepare\*() call requires schemas for two or more
+    attached databases that use the same schema-pool.
+
+The size of a schema-pool never shrinks. Each schema pool always maintains 
+a number of schema objects equal to the highwater mark of schema objects
+simultaneously required by clients.
+
+This approach is preferred to allowing multiple databases to use the same
+Schema object simultaneously for three reasons:
+
+  * The Schema object is not completely read-only. For example, the 
+    Index.zIdxAff string is allocated lazily.
+  * Throughout the statement compiler, SQLite uses variables like 
+    Table.pSchema and Index.pSchema with the sqlite3SchemaToIndex() routine
+    in order to determine which attached database a Table or Index object
+    resides in. This mechanism does not work if the same Schema may be
+    used by two or more attached databases.
+  * It may be easier to modify this approach in order to allow
+    SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA connections to modify database
+    schemas, should that be required.
+
+SQLITE&#95;OPEN&#95;SHARED&#95;SCHEMA connections do not store their
+virtual-table handles in the Table.pVTable list of each table. This would not
+work, as (a) there is no guarantee that a connection will be assigned the same
+Schema object each time it requests one from a schema-pool and (b) a single
+Schema (and therefore Table) object may correspond to tables in two or more
+databases attached to a single connection. Instead, all virtual-table handles
+associated with a single database are stored in a linked-list headed at
+Db.pVTable.
@@ -1,10 +1,7 @@
+_fiddle_exec
+_fiddle_interrupt
+_fiddle_experiment
+_fiddle_the_db
 _fiddle_db_arg
 _fiddle_db_filename
-_fiddle_exec
-_fiddle_experiment
-_fiddle_interrupt
-_fiddle_main
 _fiddle_reset_db
-_fiddle_db_handle
-_fiddle_db_vfs
-_fiddle_export_db
@@ -0,0 +1,72 @@
+_sqlite3_bind_blob
+_sqlite3_bind_double
+_sqlite3_bind_int
+_sqlite3_bind_int64
+_sqlite3_bind_null
+_sqlite3_bind_parameter_count
+_sqlite3_bind_parameter_index
+_sqlite3_bind_text
+_sqlite3_changes
+_sqlite3_changes64
+_sqlite3_clear_bindings
+_sqlite3_close_v2
+_sqlite3_column_blob
+_sqlite3_column_bytes
+_sqlite3_column_count
+_sqlite3_column_count
+_sqlite3_column_double
+_sqlite3_column_int
+_sqlite3_column_int64
+_sqlite3_column_name
+_sqlite3_column_text
+_sqlite3_column_type
+_sqlite3_compileoption_get
+_sqlite3_compileoption_used
+_sqlite3_create_function_v2
+_sqlite3_data_count
+_sqlite3_db_filename
+_sqlite3_db_name
+_sqlite3_errmsg
+_sqlite3_error_offset
+_sqlite3_errstr
+_sqlite3_exec
+_sqlite3_expanded_sql
+_sqlite3_extended_errcode
+_sqlite3_extended_result_codes
+_sqlite3_finalize
+_sqlite3_initialize
+_sqlite3_interrupt
+_sqlite3_libversion
+_sqlite3_libversion_number
+_sqlite3_open
+_sqlite3_open_v2
+_sqlite3_prepare_v2
+_sqlite3_prepare_v3
+_sqlite3_reset
+_sqlite3_result_blob
+_sqlite3_result_double
+_sqlite3_result_error
+_sqlite3_result_error_code
+_sqlite3_result_error_nomem
+_sqlite3_result_error_toobig
+_sqlite3_result_int
+_sqlite3_result_null
+_sqlite3_result_text
+_sqlite3_sourceid
+_sqlite3_sql
+_sqlite3_step
+_sqlite3_strglob
+_sqlite3_strlike
+_sqlite3_total_changes
+_sqlite3_total_changes64
+_sqlite3_value_blob
+_sqlite3_value_bytes
+_sqlite3_value_double
+_sqlite3_value_text
+_sqlite3_value_type
+_sqlite3_vfs_find
+_sqlite3_vfs_register
+_sqlite3_wasm_db_error
+_sqlite3_wasm_enum_json
+_malloc
+_free
@@ -1,155 +0,0 @@
-_malloc
-_free
-_realloc
-_sqlite3_aggregate_context
-_sqlite3_auto_extension
-_sqlite3_bind_blob
-_sqlite3_bind_double
-_sqlite3_bind_int
-_sqlite3_bind_int64
-_sqlite3_bind_null
-_sqlite3_bind_parameter_count
-_sqlite3_bind_parameter_index
-_sqlite3_bind_parameter_name
-_sqlite3_bind_pointer
-_sqlite3_bind_text
-_sqlite3_busy_handler
-_sqlite3_busy_timeout
-_sqlite3_cancel_auto_extension
-_sqlite3_changes
-_sqlite3_changes64
-_sqlite3_clear_bindings
-_sqlite3_close_v2
-_sqlite3_collation_needed
-_sqlite3_column_blob
-_sqlite3_column_bytes
-_sqlite3_column_count
-_sqlite3_column_decltype
-_sqlite3_column_double
-_sqlite3_column_int
-_sqlite3_column_int64
-_sqlite3_column_name
-_sqlite3_column_text
-_sqlite3_column_type
-_sqlite3_column_value
-_sqlite3_commit_hook
-_sqlite3_compileoption_get
-_sqlite3_compileoption_used
-_sqlite3_complete
-_sqlite3_context_db_handle
-_sqlite3_create_collation
-_sqlite3_create_collation_v2
-_sqlite3_create_function
-_sqlite3_create_function_v2
-_sqlite3_data_count
-_sqlite3_db_filename
-_sqlite3_db_handle
-_sqlite3_db_name
-_sqlite3_db_readonly
-_sqlite3_db_status
-_sqlite3_deserialize
-_sqlite3_errcode
-_sqlite3_errmsg
-_sqlite3_error_offset
-_sqlite3_errstr
-_sqlite3_exec
-_sqlite3_expanded_sql
-_sqlite3_extended_errcode
-_sqlite3_extended_result_codes
-_sqlite3_file_control
-_sqlite3_finalize
-_sqlite3_free
-_sqlite3_get_auxdata
-_sqlite3_get_autocommit
-_sqlite3_initialize
-_sqlite3_interrupt
-_sqlite3_is_interrupted
-_sqlite3_keyword_count
-_sqlite3_keyword_name
-_sqlite3_keyword_check
-_sqlite3_last_insert_rowid
-_sqlite3_libversion
-_sqlite3_libversion_number
-_sqlite3_limit
-_sqlite3_malloc
-_sqlite3_malloc64
-_sqlite3_msize
-_sqlite3_open
-_sqlite3_open_v2
-_sqlite3_overload_function
-_sqlite3_prepare_v2
-_sqlite3_prepare_v3
-_sqlite3_randomness
-_sqlite3_realloc
-_sqlite3_realloc64
-_sqlite3_reset
-_sqlite3_reset_auto_extension
-_sqlite3_result_blob
-_sqlite3_result_double
-_sqlite3_result_error
-_sqlite3_result_error_code
-_sqlite3_result_error_nomem
-_sqlite3_result_error_toobig
-_sqlite3_result_int
-_sqlite3_result_int64
-_sqlite3_result_null
-_sqlite3_result_pointer
-_sqlite3_result_subtype
-_sqlite3_result_text
-_sqlite3_result_zeroblob
-_sqlite3_result_zeroblob64
-_sqlite3_rollback_hook
-_sqlite3_serialize
-_sqlite3_set_auxdata
-_sqlite3_set_last_insert_rowid
-_sqlite3_shutdown
-_sqlite3_sourceid
-_sqlite3_sql
-_sqlite3_status
-_sqlite3_status64
-_sqlite3_step
-_sqlite3_stmt_busy
-_sqlite3_stmt_explain
-_sqlite3_stmt_isexplain
-_sqlite3_stmt_readonly
-_sqlite3_stmt_status
-_sqlite3_strglob
-_sqlite3_stricmp
-_sqlite3_strlike
-_sqlite3_strnicmp
-_sqlite3_table_column_metadata
-_sqlite3_total_changes
-_sqlite3_total_changes64
-_sqlite3_trace_v2
-_sqlite3_txn_state
-_sqlite3_update_hook
-_sqlite3_uri_boolean
-_sqlite3_uri_int64
-_sqlite3_uri_key
-_sqlite3_uri_parameter
-_sqlite3_user_data
-_sqlite3_value_blob
-_sqlite3_value_bytes
-_sqlite3_value_double
-_sqlite3_value_dup
-_sqlite3_value_free
-_sqlite3_value_frombind
-_sqlite3_value_int
-_sqlite3_value_int64
-_sqlite3_value_nochange
-_sqlite3_value_numeric_type
-_sqlite3_value_pointer
-_sqlite3_value_subtype
-_sqlite3_value_text
-_sqlite3_value_type
-_sqlite3_vfs_find
-_sqlite3_vfs_register
-_sqlite3_vfs_unregister
-_sqlite3_vtab_collation
-_sqlite3_vtab_distinct
-_sqlite3_vtab_in
-_sqlite3_vtab_in_first
-_sqlite3_vtab_in_next
-_sqlite3_vtab_nochange
-_sqlite3_vtab_on_conflict
-_sqlite3_vtab_rhs_value
@@ -1,4 +1,3 @@
-//#ifnot omit-oo1
 /*
  2022-08-24

@@ -42,13 +41,9 @@
   - `onready` (optional, but...): this callback is called with no
   arguments when the worker fires its initial
   'sqlite3-api'/'worker1-ready' message, which it does when
-   sqlite3.initWorker1API() completes its initialization. This is the
-   simplest way to tell the worker to kick off work at the earliest
-   opportunity, and the only way to know when the worker module has
-   completed loading. The irony of using a callback for this, instead
-   of returning a promise from sqlite3Worker1Promiser() is not lost on
-   the developers: see sqlite3Worker1Promiser.v2() which uses a
-   Promise instead.
+   sqlite3.initWorker1API() completes its initialization. This is
+   the simplest way to tell the worker to kick off work at the
+   earliest opportunity.

   - `onunhandled` (optional): a callback which gets passed the
   message event object for any worker.onmessage() events which
@@ -119,7 +114,7 @@
   by all client code except that which tests this API. The `row`
   property contains the row result in the form implied by the
   `rowMode` option (defaulting to `'array'`). The `rowNumber` is a
-   1-based integer value incremented by 1 on each call into the
+   1-based integer value incremented by 1 on each call into th 
   callback.

   At the end of the result set, the same event is fired with
@@ -127,17 +122,8 @@
   the end of the result set has been reached. Note that the rows
   arrive via worker-posted messages, with all the implications
   of that.
-
-   Notable shortcomings:
-
-   - This API was not designed with ES6 modules in mind. Neither Firefox
-     nor Safari support, as of March 2023, the {type:"module"} flag to the
-     Worker constructor, so that particular usage is not something we're going
-     to target for the time being:
-
-     https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker
 */
-globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfig){
+self.sqlite3Worker1Promiser = function callee(config = callee.defaultConfig){
  // Inspired by: https://stackoverflow.com/a/52439530
  if(1===arguments.length && 'function'===typeof arguments[0]){
    const f = config;
@@ -160,7 +146,6 @@ globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfi
  if(!config.worker) config.worker = callee.defaultConfig.worker;
  if('function'===typeof config.worker) config.worker = config.worker();
  let dbId;
-  let promiserFunc;
  config.worker.onmessage = function(ev){
    ev = ev.data;
    debug('worker1.onmessage',ev);
@@ -168,14 +153,14 @@ globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfi
    if(!msgHandler){
      if(ev && 'sqlite3-api'===ev.type && 'worker1-ready'===ev.result) {
        /*fired one time when the Worker1 API initializes*/
-        if(config.onready) config.onready(promiserFunc);
+        if(config.onready) config.onready();
        return;
      }
      msgHandler = handlerMap[ev.type] /* check for exec per-row callback */;
      if(msgHandler && msgHandler.onrow){
        msgHandler.onrow(ev);
        return;
-      }
+      }        
      if(config.onunhandled) config.onunhandled(arguments[0]);
      else err("sqlite3Worker1Promiser() unhandled worker message:",ev);
      return;
@@ -197,19 +182,19 @@ globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfi
    try {msgHandler.resolve(ev)}
    catch(e){msgHandler.reject(e)}
  }/*worker.onmessage()*/;
-  return promiserFunc = function(/*(msgType, msgArgs) || (msgEnvelope)*/){
+  return function(/*(msgType, msgArgs) || (msgEnvelope)*/){
    let msg;
    if(1===arguments.length){
      msg = arguments[0];
    }else if(2===arguments.length){
-      msg = Object.create(null);
-      msg.type = arguments[0];
-      msg.args = arguments[1];
-      msg.dbId = msg.args.dbId;
+      msg = {
+        type: arguments[0],
+        args: arguments[1]
+      };
    }else{
-      toss("Invalid arguments for sqlite3Worker1Promiser()-created factory.");
+      toss("Invalid arugments for sqlite3Worker1Promiser()-created factory.");
    }
-    if(!msg.dbId && msg.type!=='open') msg.dbId = dbId;
+    if(!msg.dbId) msg.dbId = dbId;
    msg.messageId = genMsgId(msg);
    msg.departureTime = performance.now();
    const proxy = Object.create(null);
@@ -251,13 +236,10 @@ globalThis.sqlite3Worker1Promiser = function callee(config = callee.defaultConfi
    return p;
  };
 }/*sqlite3Worker1Promiser()*/;
-
-globalThis.sqlite3Worker1Promiser.defaultConfig = {
+self.sqlite3Worker1Promiser.defaultConfig = {
  worker: function(){
-//#if target=es6-module
-    return new Worker(new URL("sqlite3-worker1-bundler-friendly.mjs", import.meta.url),{
-      type: 'module'
-    });
+//#if target=es6-bundler-friendly
+    return new Worker("sqlite3-worker1.js");
 //#else
    let theJs = "sqlite3-worker1.js";
    if(this.currentScript){
@@ -265,82 +247,17 @@ globalThis.sqlite3Worker1Promiser.defaultConfig = {
      src.pop();
      theJs = src.join('/')+'/' + theJs;
      //sqlite3.config.warn("promiser currentScript, theJs =",this.currentScript,theJs);
-    }else if(globalThis.location){
-      //sqlite3.config.warn("promiser globalThis.location =",globalThis.location);
-      const urlParams = new URL(globalThis.location.href).searchParams;
+    }else{
+      //sqlite3.config.warn("promiser self.location =",self.location);
+      const urlParams = new URL(self.location.href).searchParams;
      if(urlParams.has('sqlite3.dir')){
        theJs = urlParams.get('sqlite3.dir') + '/' + theJs;
      }
    }
-    return new Worker(theJs + globalThis.location.search);
+    return new Worker(theJs + self.location.search);
 //#endif
-  }
-//#ifnot target=es6-module
-  .bind({
-    currentScript: globalThis?.document?.currentScript
-  })
-//#endif
-  ,
+  }.bind({
+    currentScript: self?.document?.currentScript
+  }),
  onerror: (...args)=>console.error('worker1 promiser error',...args)
-}/*defaultConfig*/;
-
-/**
-   sqlite3Worker1Promiser.v2(), added in 3.46, works identically to
-   sqlite3Worker1Promiser() except that it returns a Promise instead
-   of relying an an onready callback in the config object. The Promise
-   resolves to the same factory function which
-   sqlite3Worker1Promiser() returns.
-
-   If config is-a function or is an object which contains an onready
-   function, that function is replaced by a proxy which will resolve
-   after calling the original function and will reject if that
-   function throws.
-*/
-sqlite3Worker1Promiser.v2 = function(config){
-  let oldFunc;
-  if( 'function' == typeof config ){
-    oldFunc = config;
-    config = {};
-  }else if('function'===typeof config?.onready){
-    oldFunc = config.onready;
-    delete config.onready;
-  }
-  const promiseProxy = Object.create(null);
-  config = Object.assign((config || Object.create(null)),{
-    onready: async function(func){
-      try {
-        if( oldFunc ) await oldFunc(func);
-        promiseProxy.resolve(func);
-      }
-      catch(e){promiseProxy.reject(e)}
-    }
-  });
-  const p = new Promise(function(resolve,reject){
-    promiseProxy.resolve = resolve;
-    promiseProxy.reject = reject;
-  });
-  try{
-    this.original(config);
-  }catch(e){
-    promiseProxy.reject(e);
-  }
-  return p;
-}.bind({
-   /* We do this because clients are
-      recommended to delete globalThis.sqlite3Worker1Promiser. */
-  original: sqlite3Worker1Promiser
-});
-
-//#if target=es6-module
-/**
-  When built as a module, we export sqlite3Worker1Promiser.v2()
-  instead of sqlite3Worker1Promise() because (A) its interface is more
-  conventional for ESM usage and (B) the ESM export option for this
-  API did not exist until v2 was created, so there's no backwards
-  incompatibility.
-*/
-export default sqlite3Worker1Promiser.v2;
-//#endif /* target=es6-module */
-//#else
-/* Built with the omit-oo1 flag. */
-//#endif ifnot omit-oo1
+};
@@ -115,7 +115,6 @@ delete globalThis.sqlite3Worker1Promiser;
            "insert into t(a,b) values(1,2),(3,4),(5,6)"
           ].join(';'),
      resultRows: [], columnNames: [],
-      lastInsertRowId: true,
      countChanges: sqConfig.bigIntEnabled ? 64 : true
    }, function(ev){
      ev = ev.result;
@@ -123,9 +122,7 @@ delete globalThis.sqlite3Worker1Promiser;
        .assert(0===ev.columnNames.length)
        .assert(sqConfig.bigIntEnabled
                ? (3n===ev.changeCount)
-                : (3===ev.changeCount))
-        .assert('bigint'===typeof ev.lastInsertRowId)
-        .assert(ev.lastInsertRowId>=3);
+                : (3===ev.changeCount));
    });

    await wtest('exec',{
@@ -5,10 +5,11 @@
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>SQLite3 Fiddle</title>
    <link rel="shortcut icon" href="data:image/x-icon;," type="image/x-icon">
-    <!-- to add a toggleable terminal-style view, uncomment the following
+    <!-- to add a togglable terminal-style view, uncomment the following
         two lines and ensure that these files are on the web server. -->
    <!--script src="jqterm/jqterm-bundle.min.js"></script>
    <link rel="stylesheet" href="jqterm/jquery.terminal.min.css"/-->
+    <link rel="stylesheet" href="emscripten.css"/>
    <style>
      /* The following styles are for app-level use. */
      :root {
@@ -170,31 +171,6 @@
          display: flex;
          flex-direction: column-reverse;
      }
-
-      /* emcscript-related styling, used during the module load/intialization processes... */
-      .emscripten { padding-right: 0; margin-left: auto; margin-right: auto; display: block; }
-      div.emscripten { text-align: center; }
-      div.emscripten_border { border: 1px solid black; }
-      #module-spinner { overflow: visible; }
-      #module-spinner > * {
-          margin-top: 1em;
-      }
-      .spinner {
-          height: 50px;
-          width: 50px;
-          margin: 0px auto;
-          animation: rotation 0.8s linear infinite;
-          border-left: 10px solid rgb(0,150,240);
-          border-right: 10px solid rgb(0,150,240);
-          border-bottom: 10px solid rgb(0,150,240);
-          border-top: 10px solid rgb(100,0,200);
-          border-radius: 100%;
-          background-color: rgb(200,100,250);
-      }
-      @keyframes rotation {
-          from {transform: rotate(0deg);}
-          to {transform: rotate(360deg);}
-      }
    </style>
  </head>
  <body>
@@ -297,6 +273,11 @@
        </fieldset>
      </div>
    </div> <!-- #view-split -->
+    <!-- Maintenance notes:
+
+        ... TODO... currently being refactored...
+
+    -->
    <script src="fiddle.js"></script>
  </body>
 </html>
@@ -725,6 +725,7 @@ TESTSRC = \
  $(TOP)/src/test_quota.c \
  $(TOP)/src/test_rtree.c \
  $(TOP)/src/test_schema.c \
+  $(TOP)/src/test_schemapool.c \
  $(TOP)/src/test_superlock.c \
  $(TOP)/src/test_syscall.c \
  $(TOP)/src/test_tclsh.c \
@@ -792,6 +793,8 @@ TESTSRC2 = \
  $(TOP)/src/bitvec.c \
  $(TOP)/src/btree.c \
  $(TOP)/src/build.c \
+  $(TOP)/src/callback.c \
+  $(TOP)/src/ctime.c \
  ctime.c \
  $(TOP)/src/date.c \
  $(TOP)/src/dbpage.c \
@@ -1,11 +1,11 @@
-C Internal\sconfigure\sscript\scleanups.\sResolve\san\sas-yet-hypothetical\scorner\scase\sinvolving\sthe\s--dev\sflag\smixed\swith\scustom\sCFLAGS\scontaining\sSQLITE_ENABLE...\sor\sSQLITE_OMIT...\sflags.\sFix\san\sunrelated\sAPI\sdoc\stypo\sreported\sin\s[forum:606ea661df|forum\spost\s606ea661df].
-D 2025-03-03T14:15:13.905
+C Improvement\soutput\sfor\s".schema\s--indent"\sin\sthe\sCLI\swhen\sthe\sschema\scontains\npartial\sindexes\swith\slong\sand\scomplicated\sWHERE\sclauses.
+D 2025-03-05T16:30:36.389
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
 F Makefile.in 4ff9b301b59c66ef9d11c8d133cc62e09173bad4abc7d5eb801e45d5527f8fe6
 F Makefile.linux-generic bd3e3cacd369821a6241d4ea1967395c962dfe3057e38cb0a435cee0e8b789d0
-F Makefile.msc ef04498c7e227a0f459b105bb4952f26cc985d1d6340a367e62d5a79c4689dfb
+F Makefile.msc 40a852813c2c84efd579f34b881f9169020284ac80d3d56463b88158e2f1c00e
 F README.md a953c0cffd6e4f2501a306c00ee2b6e1e6630c25031e094629307fe99dd003d1
 F VERSION 001dea55eb8304ec9130b6b44a32d3fc349f279d45a7e224fc0730c3cb8e2372
 F art/icon-243x273.gif 9750b734f82fdb3dc43127753d5e6fbf3b62c9f4e136c2fbf573b2f57ea87af5
@@ -59,8 +59,9 @@ F doc/compile-for-unix.md c9dce1ddd4bf0d25efccc5c63eb047e78c01ce06a6ff29c73e0a8a
 F doc/compile-for-windows.md 5141661e783c9ca9e3fd30e813345898712f5c311d71316f183db87038fa28a6
 F doc/json-enhancements.md e356fc834781f1f1aa22ee300027a270b2c960122468499bf347bb123ce1ea4f
 F doc/jsonb.md ede3238186e3a90bb79d20b2a6a06d0f9429a38e069e9da0efbad0f2ed48b924
-F doc/lemon.html 7504a6dc9b56dd376a046833ea9cc8b08def93f19bfad6eab9f1a365a4b5f49a
+F doc/lemon.html 6aa6b6a75890bc71a6ad2b94e0723c273818b8b5e43b591eb483a6db0838441f
 F doc/pager-invariants.txt 83aa3a4724b2d7970cc3f3461f0295c46d4fc19a835a5781cbb35cb52feb0577
+F doc/shared_schema.md 759fc374709fccf4e5d2d0cbd05f8fedd38fb022bdd8a6c5b5f492684c7023b9
 F doc/tcl-extension-testing.md 864875c3b672db79e7d42348dd726f9a4fbd852b1d8e5efcf09fe3d1ff6bf2a2
 F doc/testrunner.md 15583cf8c7d8a1c3378fd5d4319ca769a14c4d950a5df9b015d01d5be290dc69
 F doc/trusted-schema.md 33625008620e879c7bcfbbfa079587612c434fa094d338b08242288d358c3e8a
@@ -618,7 +619,7 @@ F ext/session/sessionwor.test 6fd9a2256442cebde5b2284936ae9e0d54bde692d0f5fd009e
 F ext/session/sqlite3session.c 8011b9531c7dd8dce55226def022f3303ce40d0b45966877f2c35185f4b1c3fc
 F ext/session/sqlite3session.h aa5de3ec8ef0e5313e9f65dafd69e8ba292d170f07b57da9200c040068dab061
 F ext/session/test_session.c 12e0a2c15fd60f92da4bb29c697c9177ff0c0dbcdc5129a54c47e999f147937a
-F ext/wasm/EXPORTED_FUNCTIONS.fiddle.in 27450c8b8c70875a260aca55435ec927068b34cef801a96205adb81bdcefc65c
+F ext/wasm/EXPORTED_FUNCTIONS.fiddle 7fb73f7150ab79d83bb45a67d257553c905c78cd3d693101699243f36c5ae6c3
 F ext/wasm/GNUmakefile 24d7e6f446528fa67f5ade6c3c7d7e46e1ac52649d6264cbe24539c1dab608e1
 F ext/wasm/README-dist.txt f01081a850ce38a56706af6b481e3a7878e24e42b314cfcd4b129f0f8427066a
 F ext/wasm/README.md b89605f65661cf35bf034ff6d43e448cc169b8017fc105d498e33b81218b482c
@@ -627,7 +628,7 @@ F ext/wasm/SQLTester/SQLTester.mjs 66e1adc3d79467b68e3e40614fd42c1a577c7e219ec09
 F ext/wasm/SQLTester/SQLTester.run.mjs 57f2adb33f43f2784abbf8026c1bfd049d8013af1998e7dcb8b50c89ffc332e0
 F ext/wasm/SQLTester/index.html 64f3435084c7d6139b08d1f2a713828a73f68de2ae6a3112cbb5980d991ba06f
 F ext/wasm/SQLTester/touint8array.c 2d5ece04ec1393a6a60c4bf96385bda5e1a10ad49f3038b96460fc5e5aa7e536
-F ext/wasm/api/EXPORTED_FUNCTIONS.sqlite3-core 2bcbbfe3b95c043ed6037e2708a2ee078d212dd1612c364f93588d8dc97300fe
+F ext/wasm/api/EXPORTED_FUNCTIONS.sqlite3-api c5eaceabb9e759aaae7d3101a4a3e542f96ab2c99d89a80ce20ec18c23115f33
 F ext/wasm/api/EXPORTED_FUNCTIONS.sqlite3-extras fe40d6d758646e38f8b15f709044951e10884214f5453d35502100179c388c13
 F ext/wasm/api/EXPORTED_FUNCTIONS.sqlite3-see fb29e62082a658f0d81102488414d422c393c4b20cc2f685b216bc566237957b
 F ext/wasm/api/EXPORTED_RUNTIME_METHODS.sqlite3-api 1ec3c73e7d66e95529c3c64ac3de2470b0e9e7fbf7a5b41261c367cf4f1b7287
@@ -649,7 +650,7 @@ F ext/wasm/api/sqlite3-vfs-opfs-sahpool.c-pp.js 16d80af915bfd2529824b999b3044255
 F ext/wasm/api/sqlite3-vfs-opfs.c-pp.js 4ab0704ee198de7d1059eccedc7703c931510b588d10af0ee36ea5b3ebbac284
 F ext/wasm/api/sqlite3-vtab-helper.c-pp.js e809739d71e8b35dfe1b55d24d91f02d04239e6aef7ca1ea92a15a29e704f616
 F ext/wasm/api/sqlite3-wasm.c 6a4cd40267eaf08400895c5b9de39c56976c3b97b3c1bbe53fc2e80fa074e9c7
-F ext/wasm/api/sqlite3-worker1-promiser.c-pp.js bc65debfe43b81fc39fb25c40ad0cc1946bd82580fbf644351107b544d6177ee
+F ext/wasm/api/sqlite3-worker1-promiser.c-pp.js c5ac33e39f21a3481812d7333ca6e18853640d423a01960ca8dbc6e7c5c3c21c
 F ext/wasm/api/sqlite3-worker1.c-pp.js 5e8706c2c4af2a57fbcdc02f4e7ef79869971bc21bb8ede777687786ce1c92d5
 F ext/wasm/batch-runner-sahpool.html e9a38fdeb36a13eac7b50241dfe7ae066fe3f51f5c0b0151e7baee5fce0d07a7
 F ext/wasm/batch-runner-sahpool.js 54a3ac228e6c4703fe72fb65c897e19156263a51fe9b7e21d2834a45e876aabd
@@ -667,15 +668,15 @@ F ext/wasm/demo-123.js c7b3cca50c55841c381a9ca4f9396e5bbdc6114273d0b10a43e378e32
 F ext/wasm/demo-jsstorage.html 409c4be4af5f207fb2877160724b91b33ea36a3cd8c204e8da1acb828ffe588e
 F ext/wasm/demo-jsstorage.js 42131ddfa18e817d0e39ac63745e9ea31553980a5ebd2222e04d4fac60c19837
 F ext/wasm/demo-worker1-promiser.c-pp.html 635cf90685805e21772a5f7a35d1ace80f98a9ef7c42ff04d7a125ddca7e5db8
-F ext/wasm/demo-worker1-promiser.c-pp.js af168699d3cab1c27ad2364ebe06cd49db300bdbf404e23b00d5742ed52816ba
+F ext/wasm/demo-worker1-promiser.c-pp.js fcc628cb42fcfaf07d250477801de1e6deb1e319d003976612a0db8d76b9fccc
 F ext/wasm/demo-worker1.html 2c178c1890a2beb5a5fecb1453e796d067a4b8d3d2a04d65ca2eb1ab2c68ef5d
 F ext/wasm/demo-worker1.js 08720227e98fa5b44761cf6e219269cee3e9dd0421d8d91459535da776950314
 F ext/wasm/dist.make 92ef4ffe33022a50f92d602acabad10bd8dd91759f3eb7df27fc6d7d37072b96
 F ext/wasm/example_extra_init.c 2347cd69d19d839ef4e5e77b7855103a7fe3ef2af86f2e8c95839afd8b05862f
 F ext/wasm/fiddle.make c6d7a3d6cc03bb5f21acb295c1233820d0dbf5c6a89b28dc2e093edcc001c45a
 F ext/wasm/fiddle/fiddle-worker.js 850e66fce39b89d59e161d1abac43a181a4caa89ddeea162765d660277cd84ce
+F ext/wasm/fiddle/fiddle.html 550c5aafce40bd218de9bf26192749f69f9b10bc379423ecd2e162bcef885c08
 F ext/wasm/fiddle/fiddle.js 2a2f27b4be2674f501fff61c4a09e44dcf2295731a26b5c28e439f3a573bd269
-F ext/wasm/fiddle/index.html 7fcfb221165183bef0e05d5af9ceb79b527e799b1708ab05de0ec0eaebd5b7bf
 F ext/wasm/index-dist.html 56132399702b15d70c474c3f1952541e25cb0922942868f70daf188f024b3730
 F ext/wasm/index.html bcaa00eca521b372a6a62c7e7b17a870b0fcdf3e418a5921df1fd61e5344080d
 F ext/wasm/jaccwabyt/jaccwabyt.js 6e4f26d0edb5c2e7d381b7eff1924832a040a12274afab2d1e1789027e9f6c5c
@@ -705,7 +706,7 @@ F ext/wasm/tests/opfs/sahpool/sahpool-pausing.js f264925cfc82155de38cecb3d204c36
 F ext/wasm/tests/opfs/sahpool/sahpool-worker.js bd25a43fc2ab2d1bafd8f2854ad3943ef673f7c3be03e95ecf1612ff6e8e2a61
 F ext/wasm/wasmfs.make 68999f5bd8c489239592d59a420f8c627c99169bbd6fa16a404751f757b9f702
 F magic.txt 5ade0bc977aa135e79e3faaea894d5671b26107cc91e70783aa7dc83f22f3ba0
-F main.mk 8a75d3cc70549d2a876eab2666eb82832335a3539822359d612b56e355fdf344
+F main.mk 178381be0b2cdcb14f49af1e0b0b679b6626089df9da097563333a265c67db32
 F mptest/config01.test 3c6adcbc50b991866855f1977ff172eb6d901271
 F mptest/config02.test 4415dfe36c48785f751e16e32c20b077c28ae504
 F mptest/crash01.test 61e61469e257df0850df4293d7d4d6c2af301421
@@ -715,9 +716,9 @@ F mptest/multiwrite01.test dab5c5f8f9534971efce679152c5146da265222d
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 acdff36db796e2d00225b911d3047d580cd136547298435426ce9d40347973cc
 F sqlite3.pc.in 0977c03a4da7c4204bd60e784a0efb8d51a190448aba78a4e973fe7192bdaf03
-F src/alter.c 0d2122ade76617b7cca383428d0881a9821ef8ddaf9cce6ff91d69a215614b95
-F src/analyze.c 13895d4da6ac857d95d3291dc607d492eba3ea1cbc3bc04baaa0383fbc1bb3d4
-F src/attach.c 9af61b63b10ee702b1594ecd24fb8cea0839cfdb6addee52fba26fa879f5db9d
+F src/alter.c 4b855e10b66524fe39f3cc0fc19500593e0a0d7e9c77c17a5a8ad689356230e4
+F src/analyze.c b8662a13798064f01eef20d3f59e83f9f5b1860de131b526aec298180601f2de
+F src/attach.c 82a709d96b7043d9c9c52589e77ee5420415809d765405b0cc2f35894dd3fb13
 F src/auth.c 54ab9c6c5803b47c0d45b76ce27eff22a03b4b1f767c5945a3a4eb13aa4c78dc
 F src/backup.c 5c97e8023aab1ce14a42387eb3ae00ba5a0644569e3476f38661fa6f824c3523
 F src/bitvec.c 782cc29b42b47e7ec6348eb0aaf9ffe60063f498387e7249f458d445af4b53e9
@@ -725,8 +726,8 @@ F src/btmutex.c 30dada73a819a1ef5b7583786370dce1842e12e1ad941e4d05ac29695528daea
 F src/btree.c 00fcee37947641f48d4b529d96143e74d056b7afa8f26d61292c90ee59c056b2
 F src/btree.h 18e5e7b2124c23426a283523e5f31a4bff029131b795bb82391f9d2f3136fc50
 F src/btreeInt.h 9c0f9ea5c9b5f4dcaea18111d43efe95f2ac276cd86d770dce10fd99ccc93886
-F src/build.c 20793695ef64d2d0c147501e37f344f828f09f16d346a987b516316186030996
-F src/callback.c acae8c8dddda41ee85cfdf19b926eefe830f371069f8aadca3aa39adf5b1c859
+F src/build.c 259abd6d09b8692553bfa7670ff807091af1219d44d3ee467e283b99656878e0
+F src/callback.c dd68d54c81989e9ba846464ffc5cc122ac83fe6686fabc6cf38d9e0f480c6879
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/date.c 9db4d604e699a73e10b8e85a44db074a1f04c0591a77e2abfd77703f50dce1e9
 F src/dbpage.c 2e677acb658a29965e55398bbc61161cb7819da538057c8032adac7ab8e4a8c0
@@ -745,7 +746,7 @@ F src/insert.c a5f0366266be993ebf533808f22cb7a788624805b55bc45424ceed3f48c54a16
 F src/json.c 81e2012796a0e139b18c50ee3444c8ef86a020ab360511882216f5b610657e0c
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 7432c944ff197046d67a1207790a1b13eec4548c85a9457eb0896bb3641dfb36
-F src/main.c 5102588cbe7668d5ee19fd9945546e4f1fd99e41815432decf5dd29f01f55597
+F src/main.c 65ffb80350bf390245de6222bade5fcc69a4a93b8b70b880ec68b7776dd21ca0
 F src/malloc.c 410e570b30c26cc36e3372577df50f7a96ee3eed5b2b161c6b6b48773c650c5e
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c 3bb59158c38e05f6270e761a9f435bf19827a264c13d1631c58b84bdc96d73b2
@@ -767,30 +768,30 @@ F src/os_common.h 6c0eb8dd40ef3e12fe585a13e709710267a258e2c8dd1c40b1948a1d14582e
 F src/os_kv.c 4d39e1f1c180b11162c6dc4aa8ad34053873a639bac6baae23272fc03349986a
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 F src/os_unix.c 410185df4900817c218c0efdb8064b3481af88cb3f7cea7392f820b6eebc7889
-F src/os_win.c ab9912a2c1cb39a6429b8de919a5b63ad1c7775e511d748391c57bf9ad03bd29
+F src/os_win.c 18a345cad65013f625bc8e1d7efdea40e7be5462c7bc38e84ca5fa8b125cef5d
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c 9fbb541b46125dfa8914827575e6bb4d15048caa008073b1709112d495d7983b
+F src/pager.c 9a40b9f6b1a4530905ac78914baba69e34f4f80ce86f53b010192df644adedc2
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-F src/prepare.c 1832be043fce7d489959aae6f994c452d023914714c4d5457beaed51c0f3d126
+F src/pragma.c 22c184ba97a2d5880aae074edbcf3f862a0198b9d8f5ef1ee7ee96d883858f88
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 F src/printf.c 33fc0d7643c848a098afdcb6e1db6de12379d47084b1cd0912cfce1d09345e44
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 F src/select.c a076f7db3a0fcbd9f710d7746cfc07e0b3baadee45eb3136bedc29c598ef8f1c
-F src/shell.c.in 6bb2abfb5cbeb5b017b8d0e94e39dd1efd101b22aca07a6734b155b6d4d03f62
-F src/sqlite.h.in 3db05f6603c78d9e6fe035e9e12bed4ca8140135d05ff092becc2cf7d7d1fefb
+F src/shell.c.in 5366b2a071d41784ce9bc87891c0d04cb469b122cdb632bafca3fad8d26a0b80
+F src/sqlite.h.in 7c58f9f9f7ed6d30d0783162f7d9f12ede11e833bac77b176aaa28aeca77bb12
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 3f046c04ea3595d6bfda99b781926b17e672fd6d27da2ba6d8d8fc39981dcb54
-F src/sqliteInt.h 130217107c0425ab43d098c6eadf8aa2e1a037e26d79384127e2d950b27eec77
+F src/sqliteInt.h b6c47ecbe197adb620ce3d43415ff2d2519e53a5d634ec9c055ee193df72776c
 F src/sqliteLimit.h 6d817c28a8f19af95e6f4921933b7fbbca48a962bce0eb0ec81e8bb3ef38e68b
-F src/status.c 0e72e4f6be6ccfde2488eb63210297e75f569f3ce9920f6c3d77590ec6ce5ffd
+F src/status.c 9adeef15f9b2bd4a72ccd22b1f29e34dea6ca898baf420016332ba7e63f55539
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
-F src/tclsqlite.c 5c1e367e26711044730c93d4b81312170918a8d1fe811f45be740ab48f7de8c1
+F src/tclsqlite.c 09d33ad9a35929f997d7152e9aa1d4d62757ce6e73d237dbe33f11261e4778ae
 F src/tclsqlite.h 65e2c761446e1c9fa0342b7d2612a703483643c8b6a316d12a65b745a4727395
 F src/test1.c ba7b93478a6a7a3f48ec5507f28bc662636ac5d9f9791700d3648a8e788f0bb2
 F src/test2.c 7ebc518e6735939d8979273a6f7b1d9b5702babf059f6ad62499f7f60a9eb9a3
@@ -805,7 +806,7 @@ F src/test_backup.c bd901e3c116c7f3b3bbbd4aae4ce87d99b400c9cbb0a9e7b4610af451d97
 F src/test_bestindex.c 3401bee51665cbf7f9ed2552b5795452a8b86365e4c9ece745b54155a55670c6
 F src/test_blob.c bcdf6a6c22d0bcc13c41479d63692ef413add2a4d30e1e26b9f74ab85b9fb4d5
 F src/test_btree.c 28283787d32b8fa953eb77412ad0de2c9895260e4e5bd5a94b3c7411664f90d5
-F src/test_config.c 7f412406592794636d6226268e26d413850a9f799bc5f3c01afc2820b165fca8
+F src/test_config.c 8b48024b0f240f1824ba801b72048c9a6344109292ee33a8eb7339d1a3689956
 F src/test_delete.c e2fe07646dff6300b48d49b2fee2fe192ed389e834dd635e3b3bac0ce0bf9f8f
 F src/test_demovfs.c 3efa2adf4f21e10d95521721687d5ca047aea91fa62dd8cc22ac9e5a9c942383
 F src/test_devsym.c 649434ed34d0b03fbd5a6b42df80f0f9a7e53f94dd1710aad5dd8831e91c4e86
@@ -829,10 +830,11 @@ F src/test_quota.c 744552848d9c5c5de3920d1c44b03d425a4123a223310567a199c7e0d3fe8
 F src/test_quota.h 2a8ad1952d1d2ca9af0ce0465e56e6c023b5e15d
 F src/test_rtree.c d844d746a3cc027247318b970025a927f14772339c991f40e7911583ea5ed0d9
 F src/test_schema.c b06d3ddc3edc173c143878f3edb869dd200d57d918ae2f38820534f9a5e3d7d9
+F src/test_schemapool.c fc6c14f7a20fcf4fb76e56c7ce3a3bc7056e105efeb11a6476172d5d576b920d
 F src/test_sqllog.c 540feaea7280cd5f926168aee9deb1065ae136d0bbbe7361e2ef3541783e187a
 F src/test_superlock.c 18355ca274746aa6909e3744163e5deb1196a85d5bc64b9cd377273cef626da7
 F src/test_syscall.c 9ad7ab39910c16d29411678d91b0d27a7a996a718df5ee93dcd635e846d0275c
-F src/test_tclsh.c c01706ac60bd3176754d3ccd37da74c6ad97c2e14489f8ed71b497c1c0ac0dd4
+F src/test_tclsh.c b2f529c87674301eb7ce168c6dd2d0a9030a0c75a0d88d85bcb0677195114249
 F src/test_tclvar.c ae873248a0188459b1c16ca7cc431265dacce524399e8b46725c2b3b7e048424
 F src/test_thread.c d7a8bcea7445f37cc2a1f7f81dd6059634f45e0c61bfe80182b02872fb0328bb
 F src/test_vdbecov.c 5c426d9cd2b351f5f9ceb30cabf8c64a63bfcad644c507e0bd9ce2f6ae1a3bf3
@@ -844,28 +846,28 @@ F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c 375a772e2342274f4bf73605a70633237da09deed00a9bf4c4816a56777ea7c9
 F src/treeview.c d85ce76e6d1498d781957c07cb234da6d77ce0ed2d196480d516f54dabc62279
-F src/trigger.c da3c25786870d8bf97cd46b493374c2375d1abaf20a9b0f5f8629a3f2f2ce383
+F src/trigger.c 24e5859e35eb5214ccea0da6924f0f90d41095091b0fc7247b6803e7d9a700f1
 F src/update.c 3e5e7ff66fa19ebe4d1b113d480639a24cc1175adbefabbd1a948a07f28e37cf
 F src/upsert.c 215328c3f91623c520ec8672c44323553f12caeb4f01b1090ebdca99fdf7b4f1
 F src/utf.c d4d55ca95106a2029ec1cdbd2497a34e69ea1d338f1a9d80ef15ebf4ff01690d
 F src/util.c 36fb1150062957280777655976f3f9a75db236cb8207a0770ceae8d5ec17fcd3
-F src/vacuum.c b763b6457bd058d2072ef9364832351fd8d11e8abf70cbb349657360f7d55c40
-F src/vdbe.c e7567bed441a53c4ceb48d2bdf3d1747677fc296a91e8d2a0fe8facdb9b890ce
-F src/vdbe.h 3d26d5c7660c5c7bd33ffb0d8784615072d8b23c81f8110870efe2631136bc89
+F src/vacuum.c 38577d6f45e10a984720b5219be09ca8649a0e600c2e5c11993900446caca609
+F src/vdbe.c dac8b4bf8e0a2451690aeb3a8384202e6498c8ec45477be0d0440b23fb52bce2
+F src/vdbe.h e56df3f84b08dfb60120796591af7d36fba8513a7df2605425189253f5a76d5f
 F src/vdbeInt.h 078b1c15b26587b54c1c1879d0d2f4dec812b9de4c337fed9faf73fbcc3bf091
 F src/vdbeapi.c cb8eb9e41a16f5fa3ce5b8f3910edfbba336d10156cfb7a79f92cf7bf443977b
-F src/vdbeaux.c d7ef1a0a7233589d789eda1ba9ffa4b0ea61fca9651e4f47fb4250d03d62bcaf
-F src/vdbeblob.c 9166b6eb7054e5da82e35255892fb1ed551355a4716452539e8e3ac14f25fbe3
+F src/vdbeaux.c 57b1ec1862d5d081294e3f266a20128837f21774215134b96a883b5d3cf8a70f
+F src/vdbeblob.c e14d9eca0cce3ec4fbef69cea8cc4caefb9f8d642cc4703123a56c43dfa470d3
 F src/vdbemem.c 571ae3116dbf840a62c4aaa6bc09d577dfef8ad4d3978cf37275bb5f9653217b
 F src/vdbesort.c f7ce6eb4c0e8b0273329d2f43b8b6e5ebe8f2d853fc323d5787dada702ea0b66
 F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1945f1d2e6be5927ec12c06d89b03ef2a4def34bf823
 F src/vdbevtab.c fc46b9cbd759dc013f0b3724549cc0d71379183c667df3a5988f7e2f1bd485f3
-F src/vtab.c 828221bdbeaaa6d62126ee6d07fd4ec0d09dcaea846f87ad01944d8b7e548859
+F src/vtab.c 0c2567d6caa2f1df28362eedcd29a2fbc9f4d7a7ff6b13086cc23f4e6ab239c5
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 2c69a5f92270429db72d853691b0640c76c671d5b2465396dadb9d9873e1efce
 F src/wal.h ba252daaa94f889f4b2c17c027e823d9be47ce39da1d3799886bbd51f0490452
 F src/walker.c d5006d6b005e4ea7302ad390957a8d41ed83faa177e412f89bc5600a7462a014
-F src/where.c 12cca5dfbe96e2589f951c43c0720fc58e52611787c37d85a0d9c10376202e8b
+F src/where.c 4ef72b4d791fb1b6725d6fbebd17e5a9487105864c7828a7b0311136c08786ce
 F src/whereInt.h d20cddddb1d61b18d5cb1fcfa9b77fbeebbc4afe44d996e603452a23b3009ee1
 F src/wherecode.c 5baa06f0daae7d38aca1d4814030b82ad4f127fe6bad18f0644776a474f6088b
 F src/whereexpr.c 2415c8eee5ff89a8b709d7d83d71c1ff986cd720d0520057e1d8a5371339012a
@@ -1485,7 +1487,7 @@ F test/mutex1.test 42cb5e244c3a77bb0ef2b967e06fa5e7ba7d32d90a9b20bed98f6f5ede185
 F test/mutex2.test bfeaeac2e73095b2ac32285d2756e3a65e681660
 F test/nan.test 73ea63ab43668313e2f8cc9ef9e9a966672c7934f3ce76926fbe991235d07d91
 F test/nockpt.test 8c43b25af63b0bd620cf1b003529e37b6f1dc53bd22690e96a1bd73f78dde53a
-F test/nolock.test f196cf8b8fbea4e2ca345140a2b3f3b0da45c76e
+F test/nolock.test 284c72c2b752cf3ffbfd224dfa868bd524e624d3ab5c5ef181fc49ad9df0b444
 F test/normalize.test f23b6c5926c59548635fcf39678ac613e726121e073dd902a3062fbb83903b72
 F test/notify1.test 669b2b743618efdc18ca4b02f45423d5d2304abf
 F test/notify2.test 2ecabaa1305083856b7c39cf32816b612740c161
@@ -1558,6 +1560,8 @@ F test/randexpr1.test eda062a97e60f9c38ae8d806b03b0ddf23d796df
 F test/rbu.test 168573d353cd0fd10196b87b0caa322c144ef736
 F test/rdonly.test 64e2696c322e3538df0b1ed624e21f9a23ed9ff8
 F test/readonly.test 69a7ccec846cad2e000b3539d56360d02f327061dc5e41f7f9a3e01f19719952
+F test/readonly2.test 4f4c451adf06e314c3eeed5c5e01e5df8fa10fb3cd5f537a77a48ef50ed97b84
+F test/readonlyfault.test 2b9c98ed3ac47e3f3cb00db3850b4d7fc7c857be1502a7b74985fecf50837b1e
 F test/recover.test a163a156ea9f2beea63fa83c4dcd8dea6e57b8a569fc647155e3d2754eaac1b5
 F test/regexp1.test 8f2a8bc1569666e29a4cee6c1a666cd224eb6d50e2470d1dc1df995170f3e0f1
 F test/regexp2.test 55ed41da802b0e284ac7e2fe944be3948f93ff25abbca0361a609acfed1368b5
@@ -1566,6 +1570,13 @@ F test/resetdb.test 54c06f18bc832ac6d6319e5ab23d5c8dd49fdbeec7c696d791682a8006bd
 F test/resolver01.test f4022acafda7f4d40eca94dbf16bc5fc4ac30ceb
 F test/returning1.test 212cd4111bb941a60abf608f20250db666c21eb1bc4d49217e96c87ff3ab9d1a
 F test/returningfault.test ae4c4b5e8745813287a359d9ccdb9d5c883c2e68afb18fb0767937d5de5692a4
+F test/reuse1.test b5359932592b25d2178cd1ce0cd837abb25b68aaf69c4812eb83efa490c2dd19
+F test/reuse2.test 4012db85142e2abe3d8a1186756a71ea6e7078091f7448ac2145ca7b8c18cc51
+F test/reuse3.test 890074bbfc31f71762d583ee23a22c647870b2c2e91eb1eb60c2b5a5d3d8986b
+F test/reuse4.test bf36ee3848534f64234f84389fe8f2289da353cc0535cfe62b9287e32786f755
+F test/reuse5.test bbe6cf7384ef90f134392edd93d626385ef0bf6f40eefc3d993535cd0861d83b
+F test/reuse6.test f4674f9967aee2a0b49c02832120b8b495291c0d87aae084c54e6c0cc18132fe
+F test/reusefault.test 545a21be1b80b8ccab02c3695137ab2bb1fc58ac78738b5bf33348a618ee3b2e
 F test/rollback.test 952c4d805bca96adc2be76f621ea22115fe40b330015af36fcc8028c8547fcee
 F test/rollback2.test 3f3a4e20401825017df7e7671e9f31b6de5fae5620c2b9b49917f52f8c160a8f
 F test/rollbackfault.test 0e646aeab8840c399cfbfa43daab46fd609cf04a
@@ -1646,7 +1657,7 @@ F test/shell5.test 0e5f8ce08206b9998a778cfe1989e20e47839153c05af2da29198150172e2
 F test/shell6.test e3b883b61d4916b6906678a35f9d19054861123ad91b856461e0a456273bdbb8
 F test/shell7.test 43fd8e511c533bab5232e95c7b4be93b243451709e89582600d4b6e67693d5c3
 F test/shell8.test aea51ecbcd4494c746b096aeff51d841d04d5f0dc4b62eb42427f16109b87acd
-F test/shell9.test 8742a5b390cdcef6369f5aa223e415aa4255a4129ef249b177887dc635a87209
+F test/shell9.test 8030c6246e1ca474c65eb0e955324586bfbf3448289c99ca247fc7f62006ac2c
 F test/shellA.test 079c05c11947ade4ea8d51053d3abb687ec96a3dce6680d01838519b705190c5
 F test/shmlock.test 3dbf017d34ab0c60abe6a44e447d3552154bd0c87b41eaf5ceacd408dd13fda5
 F test/shortread1.test bb591ef20f0fd9ed26d0d12e80eee6d7ac8897a3
@@ -1721,7 +1732,7 @@ F test/tabfunc01.test 7be82bd50c7ede7f01b2dd17cd1b84f352c516078222d0b067d858f081
 F test/table.test 7862a00b58b5541511a26757ea9c5c7c3f8298766e98aa099deec703d9c0a8e0
 F test/tableapi.test ecbcc29c4ab62c1912c3717c48ea5c5e59f7d64e4a91034e6148bd2b82f177f4
 F test/tableopts.test dba698ba97251017b7c80d738c198d39ab747930
-F test/tclsqlite.test ad0bbd92edabe64cc91d990a0748142fe5ab962d74ac71fa3bfa94d50d2f4c87
+F test/tclsqlite.test 350536a4233914aa437b6735e3e8e683e921a71ced8fa9fb5396057a04dbea33
 F test/tempdb.test 4cdaa23ddd8acb4d79cbb1b68ccdfd09b0537aaba909ca69a876157c2a2cbd08
 F test/tempdb2.test 353864e96fd3ae2f70773d0ffbf8b1fe48589b02c2ec05013b540879410c3440
 F test/tempfault.test 0c0d349c9a99bf5f374655742577f8712c647900
@@ -1729,9 +1740,9 @@ F test/temptable.test d2c9b87a54147161bcd1822e30c1d1cd891e5b30
 F test/temptable2.test 76821347810ecc88203e6ef0dd6897b6036ac788e9dd3e6b04fd4d1631311a16
 F test/temptable3.test d11a0974e52b347e45ee54ef1923c91ed91e4637
 F test/temptrigger.test 38f0ca479b1822d3117069e014daabcaacefffcc
-F test/tester.tcl 2f900e8c912fbbaf381e69a92258fa6023ad0b4c8907e426bebbb4585da23c61
-F test/testrunner.tcl 0ffa67806e75aa2c186c63d7d00b16bb45adb91ed6560461fda6dbe3e18c885e x
-F test/testrunner_data.tcl 6d7e7824bb36278ea65c33f7da6dd3ca101fc7d6f7a765b807dce0aa68c52521
+F test/tester.tcl d067f95c685087f9e66efa2c4cefa5d99cd72ebeab2a7dceae89cba100ad61f7
+F test/testrunner.tcl fafc60461c165a6b53a879f090423eef7005d95f9692c7df798651b55e339fe6 x
+F test/testrunner_data.tcl 6aea1cb5865f005986037c9dad4dfe48a5281ec7aa214104e8ada3199332242b
 F test/thread001.test a0985c117eab62c0c65526e9fa5d1360dd1cac5b03bde223902763274ce21899
 F test/thread002.test c24c83408e35ba5a952a3638b7ac03ccdf1ce4409289c54a050ac4c5f1de7502
 F test/thread003.test ee4c9efc3b86a6a2767516a37bd64251272560a7
@@ -1743,7 +1754,7 @@ F test/thread3.test a12656a56cdf67acb6a2ff7638826c6d6a645f79909d86df521045ad31cf
 F test/thread_common.tcl b3b19a769fe30ef5537cdfa60acd49b78f771301627720d1add2d3bac77d9039
 F test/threadtest1.c 6029d9c5567db28e6dc908a0c63099c3ba6c383b
 F test/threadtest2.c a70a8e94bef23339d34226eb9521015ef99f4df8
-F test/threadtest3.c 655bff6c0895ec03f014126aa65e808fac9aae8c5a7a7da58a510cbe8b43b781
+F test/threadtest3.c 25cb92accb4fa6d53e708d6006ed2db7a7533ef7b838ef1306455c6fe57e978a
 F test/threadtest4.c c1e67136ceb6c7ec8184e56ac61db28f96bd2925
 F test/threadtest5.c 9b4d782c58d8915d7e955ff8051f3d03628bda0d33b82971ea8c0f2f2808c421
 F test/time-wordcount.sh 8e0b0f8109367827ad5d58f5cc849705731e4b90
@@ -1918,12 +1929,13 @@ F test/triggerF.test 5d76f0a8c428ff87a4d5ed52da06f6096a2c787a1e21b846111dfac4123
 F test/triggerG.test 2b816093c91ba73c733cfa8aedcc210ad819d72a98b1da30768a3c56505233e9
 F test/triggerupfrom.test d1f9e56090408115c522bee626cc33a2f3370f627a5e341d832589d72e3aa271
 F test/trustschema1.test d2996bb284859c99956ac706160eab9f086919da738d19bfef3ac431cce8fd47
-F test/tt3_checkpoint.c ac7ca661d739280c89d9c253897df64a59a49369bd1247207ac0f655b622579d
-F test/tt3_index.c 39eec10a35f57672225be4d182862152896dee4a
-F test/tt3_lookaside1.c 0377e202c3c2a50d688cb65ba203afeda6fafeb9
+F test/tt3_checkpoint.c 69214e2ce81bbbd3c1b82c31e103607fd2e6790818aef4792957fc9cc88d067e
+F test/tt3_index.c 95592839426dc85ce5a7a57b41be2cbf3c2ec3457b9cd841a06ed5877f712c7c
+F test/tt3_lookaside1.c 2ddd99bfffeef288f0786827ef68f912f6f47ce3d3184e62f05808d8e13b920e
+F test/tt3_reuseschema.c 4d52e141f89f009028d8ab0bd1f0697d0edffa94bafc1fff0f7ad4d9d9baa549
 F test/tt3_shared.c b37d22defc944a2ac4c91c927fd06c1d48cd51e2ce9d004fe868625bd2399f93
-F test/tt3_stress.c f9a769ca8b026ecc76ee93ca8c9700a5619f8e51c581107c4053ba6ac97f616f
-F test/tt3_vacuum.c 71b254cde1fc49d6c8c44efd54f4668f3e57d7b3a8f4601ade069f75a999ba39
+F test/tt3_stress.c 077e817ac1168443b075fedb44e92db84bb4dc5bd3b6fe1aba25c94ac280b231
+F test/tt3_vacuum.c 727bfda1299b18435eeba80dee8e6ff43462146d7c1e2096cc809f01db568391
 F test/types.test bf816ce73c7dfcfe26b700c19f97ef4050d194ff
 F test/types2.test 1aeb81976841a91eef292723649b5c4fe3bc3cac
 F test/types3.test c60e89c4d6babe44b23a2ea0090f3044e549403b20648b1c6bb65a69fea5f1ed
@@ -2140,7 +2152,7 @@ F tool/genfkey.test b6afd7b825d797a1e1274f519ab5695373552ecad5cd373530c63533638a
 F tool/getlock.c f4c39b651370156cae979501a7b156bdba50e7ce
 F tool/index_usage.c f62a0c701b2c7ff2f3e21d206f093c123f222dbf07136a10ffd1ca15a5c706c5
 F tool/kvtest-speed.sh 4761a9c4b3530907562314d7757995787f7aef8f
-F tool/lemon.c f51a488369046cd4f4212d755a214a57673ded400cbeb01e298cbf63539e1d8c
+F tool/lemon.c 5f999ac3801e8b585149a5fd5c7c2bbdde3baca98985ebe68e1a41b8e19d19a4
 F tool/lempar.c bdffd3b233a4e4e78056c9c01fadd2bb3fe902435abde3bce3d769fdf0d5cca2
 F tool/libvers.c caafc3b689638a1d88d44bc5f526c2278760d9b9
 F tool/loadfts.c c3c64e4d5e90e8ba41159232c2189dba4be7b862
@@ -2156,7 +2168,7 @@ F tool/mkmsvcmin.tcl d76c45efda1cce2d4005bcea7b8a22bb752e3256009f331120fb4fecb14
 F tool/mkopcodec.tcl 33d20791e191df43209b77d37f0ff0904620b28465cca6990cf8d60da61a07ef
 F tool/mkopcodeh.tcl 2b4e6967a670ef21bf53a164964c35c6163277d002a4c6f56fa231d68c88d023
 F tool/mkopts.tcl 680f785fdb09729fd9ac50632413da4eadbdf9071535e3f26d03795828ab07fa
-F tool/mkpragmatab.tcl 3801ce32f8c55fe63a3b279f231fb26c2c1a2ea9a09d2dd599239d87a609acec
+F tool/mkpragmatab.tcl 7650ca1297ef7530179c149db50311e9c533c6accd8df3505275529a10e82137
 F tool/mkshellc.tcl 9ce74de0fa904a2c56a96f8d8b5261246bacb0eaa8d7e184f9e18ff94145ebbc
 F tool/mksourceid.c 36aa8020014aed0836fd13c51d6dc9219b0df1761d6b5f58ff5b616211b079b9
 F tool/mkspeedsql.tcl a1a334d288f7adfe6e996f2e712becf076745c97
@@ -2213,8 +2225,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P acf9babf0efc346b26c8ac02c0bd973498bf1604b47fe320de14027f9b21ed33
-R 5182bad1c42928bd1b84d01963e58063
-U stephan
-Z df301f75cd724e3f3d22ab4620a14201
+P 52b97a7ad5d944e44240f624b30a76398d10ef945d8edc4b7d7b36ed2e515327
+R 8f505da43903c156f4ae84ef87ecfc5e
+U drh
+Z 684998f2296e83c5d595e837037d9498
 # Remove this line to create a well-formed Fossil manifest.
@@ -1 +1 @@
-0554c00f32b7cc81d35340080df10ea6d66c9ff07fe749ea76cc523a4149b5c8
+94c6e8d97158fde5c8200206cf21e8acc9de8d1b4cbaf7db8d9c6a56ad6762e4
@@ -112,8 +112,8 @@ static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
  Vdbe *v = pParse->pVdbe;
  if( v ){
    sqlite3ChangeCookie(pParse, iDb);
-    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0, p5);
-    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0, p5);
+    sqlite3VdbeAddParseSchemaOp(pParse, iDb, 0, p5);
+    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse, 1, 0, p5);
  }
 }

@@ -212,6 +212,7 @@ static void openStatTable(
        ** side-effect of the CREATE TABLE statement is to leave the rootpage 
        ** of the new table in register pParse->regRoot. This is important 
        ** because the OpenWrite opcode below will be needing it. */
+        sqlite3SchemaWritable(pParse, iDb);
        sqlite3NestedParse(pParse,
            "CREATE TABLE %Q.%s(%s)", pDb->zDbSName, zTab, aTable[i].zCols
        );
@@ -224,7 +224,6 @@ static void attachFunc(
  ** way we found it.
  */
  if( rc==SQLITE_OK ){
-    sqlite3BtreeEnterAll(db);
    db->init.iDb = 0;
    db->mDbFlags &= ~(DBFLAG_SchemaKnownOk);
 #ifdef SQLITE_ENABLE_SETLK_TIMEOUT
@@ -234,11 +233,12 @@ static void attachFunc(
      sqlite3OsFileControlHint(fd, SQLITE_FCNTL_BLOCK_ON_CONNECT, &val);
    }
 #endif
-    if( !REOPEN_AS_MEMDB(db) ){
+    if( !IsSharedSchema(db) && !REOPEN_AS_MEMDB(db) ){
+      sqlite3BtreeEnterAll(db);
      rc = sqlite3Init(db, &zErrDyn);
+      sqlite3BtreeLeaveAll(db);
+      assert( zErrDyn==0 || rc!=SQLITE_OK );
    }
-    sqlite3BtreeLeaveAll(db);
-    assert( zErrDyn==0 || rc!=SQLITE_OK );
  }
  if( rc ){
    if( ALWAYS(!REOPEN_AS_MEMDB(db)) ){
@@ -329,6 +329,7 @@ static void detachFunc(
    pEntry = sqliteHashNext(pEntry);
  }

+  (void)sqlite3SchemaDisconnect(db, i, 0);
  sqlite3BtreeClose(pDb->pBt);
  pDb->pBt = 0;
  pDb->pSchema = 0;
@@ -358,7 +359,9 @@ static void codeAttach(
  sqlite3* db = pParse->db;
  int regArgs;

-  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ) goto attach_end;
+  if( (db->mDbFlags & DBFLAG_EncodingFixed)==0 ){
+    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ) goto attach_end;
+  }

  if( pParse->nErr ) goto attach_end;
  memset(&sName, 0, sizeof(NameContext));
@@ -322,6 +322,39 @@ void sqlite3NestedParse(Parse *pParse, const char *zFormat, ...){
  pParse->nested--;
 }

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+/*
+** If this database connection was opened with the SQLITE_OPEN_SHARED_SCHEMA
+** flag specified, then ensure that the database schema for database iDb
+** is loaded. Either by obtaining a Schema object from the schema-pool, or
+** by reading the contents of the sqlite_master table. Unless it is NULL, 
+** the location indicated by parameter pbUnload is set to 1 if a shared-schema 
+** is loaded.
+**
+** If the database handle was not opened with SQLITE_OPEN_SHARED_SCHEMA, or
+** if the schema for database iDb is already loaded, this function is a no-op.
+**
+** SQLITE_OK is returned if successful, or an SQLite error code otherwise. If
+** an error code is returned, (*pzErr) may be set to point to a buffer
+** containing an error message. It is the responsibility of the caller to
+** eventually free this buffer using sqlite3_free().
+*/
+int sqlite3SchemaLoad(sqlite3 *db, int iDb, int *pbUnload, char **pzErr){
+  int rc = SQLITE_OK;
+  if( IsSharedSchema(db) 
+      && DbHasProperty(db, iDb, DB_SchemaLoaded)==0 
+      && (db->init.busy==0 || (iDb!=1 && db->init.iDb==1))
+  ){
+    struct sqlite3InitInfo sv = db->init;
+    memset(&db->init, 0, sizeof(struct sqlite3InitInfo));
+    rc = sqlite3InitOne(db, iDb, pzErr, 0);
+    db->init = sv;
+    if( pbUnload && rc==SQLITE_OK && iDb!=1 ) *pbUnload = 1;
+  }
+  return rc;
+}
+#endif
+
 /*
 ** Locate the in-memory structure that describes a particular database
 ** table given the name of that table and (optionally) the name of the
@@ -340,59 +373,41 @@ Table *sqlite3FindTable(sqlite3 *db, const char *zName, const char *zDatabase){

  /* All mutexes are required for schema access.  Make sure we hold them. */
  assert( zDatabase!=0 || sqlite3BtreeHoldsAllMutexes(db) );
-  if( zDatabase ){
-    for(i=0; i<db->nDb; i++){
-      if( sqlite3StrICmp(zDatabase, db->aDb[i].zDbSName)==0 ) break;
-    }
-    if( i>=db->nDb ){
-      /* No match against the official names.  But always match "main"
-      ** to schema 0 as a legacy fallback. */
-      if( sqlite3StrICmp(zDatabase,"main")==0 ){
-        i = 0;
-      }else{
-        return 0;
-      }
-    }
-    p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
-    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
-      if( i==1 ){
-        if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0
-         || sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0
-         || sqlite3StrICmp(zName+7, &LEGACY_SCHEMA_TABLE[7])==0
-        ){
-          p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
-                              LEGACY_TEMP_SCHEMA_TABLE);
+  while(1){
+    for(i=OMIT_TEMPDB; i<db->nDb; i++){
+      int j = (i<2) ? i^1 : i;   /* Search TEMP before MAIN */
+      if( zDatabase==0 || sqlite3DbIsNamed(db, j, zDatabase) ){
+        int bUnload = 0;
+        assert( sqlite3SchemaMutexHeld(db, j, 0) );
+        if( IsSharedSchema(db) ){
+          Parse *pParse = db->pParse;
+          if( pParse && pParse->nErr==0 ){
+            pParse->rc = sqlite3SchemaLoad(db, j, &bUnload, &pParse->zErrMsg);
+            if( pParse->rc ) pParse->nErr++;
+          }
        }
-      }else{
-        if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
-          p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash,
-                              LEGACY_SCHEMA_TABLE);
+        p = sqlite3HashFind(&db->aDb[j].pSchema->tblHash, zName);
+        if( p ) return p;
+        if( bUnload ){
+          sqlite3SchemaRelease(db, j);
        }
      }
    }
-  }else{
-    /* Match against TEMP first */
-    p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash, zName);
-    if( p ) return p;
-    /* The main database is second */
-    p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, zName);
-    if( p ) return p;
-    /* Attached databases are in order of attachment */
-    for(i=2; i<db->nDb; i++){
-      assert( sqlite3SchemaMutexHeld(db, i, 0) );
-      p = sqlite3HashFind(&db->aDb[i].pSchema->tblHash, zName);
-      if( p ) break;
+    /* Not found.  If the name we were looking for was temp.sqlite_master
+    ** then change the name to sqlite_temp_master and try again. */
+    if( sqlite3StrICmp(zName, PREFERRED_SCHEMA_TABLE)==0 ){
+      zName = LEGACY_SCHEMA_TABLE;
+      continue;
    }
-    if( p==0 && sqlite3StrNICmp(zName, "sqlite_", 7)==0 ){
-      if( sqlite3StrICmp(zName+7, &PREFERRED_SCHEMA_TABLE[7])==0 ){
-        p = sqlite3HashFind(&db->aDb[0].pSchema->tblHash, LEGACY_SCHEMA_TABLE);
-      }else if( sqlite3StrICmp(zName+7, &PREFERRED_TEMP_SCHEMA_TABLE[7])==0 ){
-        p = sqlite3HashFind(&db->aDb[1].pSchema->tblHash,
-                            LEGACY_TEMP_SCHEMA_TABLE);
-      }
+    if( sqlite3StrICmp(zName, PREFERRED_TEMP_SCHEMA_TABLE)==0 ){
+      zName = LEGACY_TEMP_SCHEMA_TABLE;
+      continue;
    }
+    if( sqlite3StrICmp(zName, LEGACY_SCHEMA_TABLE)!=0 ) break;
+    if( sqlite3_stricmp(zDatabase, db->aDb[1].zDbSName)!=0 ) break;
+    zName = LEGACY_TEMP_SCHEMA_TABLE;
  }
-  return p;
+  return 0;
 }

 /*
@@ -417,6 +432,7 @@ Table *sqlite3LocateTable(
  /* Read the database schema. If an error occurs, leave an error message
  ** and code in pParse and return NULL. */
  if( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0
+   && !IsSharedSchema(db)
   && SQLITE_OK!=sqlite3ReadSchema(pParse)
  ){
    return 0;
@@ -433,9 +449,21 @@ Table *sqlite3LocateTable(
      if( pMod==0 && sqlite3_strnicmp(zName, "pragma_", 7)==0 ){
        pMod = sqlite3PragmaVtabRegister(db, zName);
      }
-      if( pMod && sqlite3VtabEponymousTableInit(pParse, pMod) ){
-        testcase( pMod->pEpoTab==0 );
-        return pMod->pEpoTab;
+      if( pMod ){
+        if( IsSharedSchema(db) && pParse->nErr==0 ){
+          int bDummy = 0;
+          pParse->rc = sqlite3SchemaLoad(db, 0, &bDummy, &pParse->zErrMsg);
+          if( pParse->rc ) pParse->nErr++;
+          (void)bDummy;
+        }
+        if( sqlite3VtabEponymousTableInit(pParse, pMod) ){
+          Table *pEpoTab = pMod->pEpoTab;
+          if( pEpoTab ){
+            assert( IsSharedSchema(db)||pEpoTab->pSchema==db->aDb[0].pSchema );
+            pEpoTab->pSchema = db->aDb[0].pSchema;  /* For SHARED_SCHEMA mode */
+          }
+          return pEpoTab;
+        }
      }
    }
 #endif
@@ -445,15 +473,13 @@ Table *sqlite3LocateTable(
    p = 0;
  }

-  if( p==0 ){
+  if( p==0 && (!IsSharedSchema(db) || pParse->nErr==0) ){
    const char *zMsg = flags & LOCATE_VIEW ? "no such view" : "no such table";
    if( zDbase ){
      sqlite3ErrorMsg(pParse, "%s: %s.%s", zMsg, zDbase, zName);
    }else{
      sqlite3ErrorMsg(pParse, "%s: %s", zMsg, zName);
    }
-  }else{
-    assert( HasRowid(p) || p->iPKey<0 );
  }

  return p;
@@ -622,11 +648,10 @@ void sqlite3ResetOneSchema(sqlite3 *db, int iDb){
    DbSetProperty(db, 1, DB_ResetWanted);
    db->mDbFlags &= ~DBFLAG_SchemaKnownOk;
  }
-
  if( db->nSchemaLock==0 ){
    for(i=0; i<db->nDb; i++){
      if( DbHasProperty(db, i, DB_ResetWanted) ){
-        sqlite3SchemaClear(db->aDb[i].pSchema);
+        sqlite3SchemaClearOrDisconnect(db, i);
      }
    }
  }
@@ -639,16 +664,17 @@ void sqlite3ResetOneSchema(sqlite3 *db, int iDb){
 void sqlite3ResetAllSchemasOfConnection(sqlite3 *db){
  int i;
  sqlite3BtreeEnterAll(db);
-  for(i=0; i<db->nDb; i++){
+  for(i=0; i<db->nDb; i=(i?i+1:2)){
    Db *pDb = &db->aDb[i];
    if( pDb->pSchema ){
      if( db->nSchemaLock==0 ){
-        sqlite3SchemaClear(pDb->pSchema);
+        sqlite3SchemaClearOrDisconnect(db, i);
      }else{
        DbSetProperty(db, i, DB_ResetWanted);
      }
    }
  }
+  sqlite3SchemaClear(db->aDb[1].pSchema);
  db->mDbFlags &= ~(DBFLAG_SchemaChange|DBFLAG_SchemaKnownOk);
  sqlite3VtabUnlockList(db);
  sqlite3BtreeLeaveAll(db);
@@ -1265,7 +1291,7 @@ void sqlite3StartTable(
  */
  if( !IN_SPECIAL_PARSE ){
    char *zDb = db->aDb[iDb].zDbSName;
-    if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+    if( !IsSharedSchema(db) && SQLITE_OK!=sqlite3ReadSchema(pParse) ){
      goto begin_table_error;
    }
    pTable = sqlite3FindTable(db, zName, zDb);
@@ -2915,7 +2941,7 @@ void sqlite3EndTable(
 #endif

    /* Reparse everything to update our internal data structures */
-    sqlite3VdbeAddParseSchemaOp(v, iDb,
+    sqlite3VdbeAddParseSchemaOp(pParse, iDb,
           sqlite3MPrintf(db, "tbl_name='%q' AND type!='trigger'", p->zName),0);

    /* Test for cycles in generated columns and illegal expressions
@@ -3487,7 +3513,7 @@ void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
  assert( pName->nSrc==1 );
  assert( pName->a[0].fg.fixedSchema==0 );
  assert( pName->a[0].fg.isSubquery==0 );
-  if( sqlite3ReadSchema(pParse) ) goto exit_drop_table;
+  if( !IsSharedSchema(db) && sqlite3ReadSchema(pParse) ) goto exit_drop_table;
  if( noErr ) db->suppressErr++;
  assert( isView==0 || isView==LOCATE_VIEW );
  pTab = sqlite3LocateTableItem(pParse, isView, &pName->a[0]);
@@ -3502,6 +3528,7 @@ void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 && iDb<db->nDb );
+  sqlite3SchemaWritable(pParse, iDb);

  /* If pTab is a virtual table, call ViewGetColumnNames() to ensure
  ** it is initialized.
@@ -3958,7 +3985,7 @@ void sqlite3CreateIndex(
  if( IN_DECLARE_VTAB && idxType!=SQLITE_IDXTYPE_PRIMARYKEY ){
    goto exit_create_index;
  }
-  if( SQLITE_OK!=sqlite3ReadSchema(pParse) ){
+  if( !IsSharedSchema(db) && SQLITE_OK!=sqlite3ReadSchema(pParse) ){
    goto exit_create_index;
  }
  if( sqlite3HasExplicitNulls(pParse, pList) ){
@@ -4455,7 +4482,7 @@ void sqlite3CreateIndex(
      if( pTblName ){
        sqlite3RefillIndex(pParse, pIndex, iMem);
        sqlite3ChangeCookie(pParse, iDb);
-        sqlite3VdbeAddParseSchemaOp(v, iDb,
+        sqlite3VdbeAddParseSchemaOp(pParse, iDb,
            sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName), 0);
        sqlite3VdbeAddOp2(v, OP_Expire, 0, 1);
      }
@@ -4607,6 +4634,7 @@ void sqlite3DropIndex(Parse *pParse, SrcList *pName, int ifExists){
    goto exit_drop_index;
  }
  iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);
+  sqlite3SchemaWritable(pParse, iDb);
 #ifndef SQLITE_OMIT_AUTHORIZATION
  {
    int code = SQLITE_DROP_INDEX;
@@ -16,6 +16,63 @@

 #include "sqliteInt.h"

+/*
+** Connections opened with the SQLITE_OPEN_SHARED_SCHEMA flag specified
+** may use SchemaPool objects for any database that is not the temp db
+** (iDb==1). For such databases (type "struct Db") there are three states
+** the Schema/SchemaPool object may be in.
+**
+**   1) pSPool==0, pSchema points to an empty object allocated by
+**      sqlite3_malloc(). DB_SchemaLoaded flag is clear.
+**
+**   2) pSPool!=0, pSchema points to a populated object owned by the
+**      SchemaPool. DB_SchemaLoaded flag is set.
+**
+**   3) pSPool!=0, pSchema points to the SchemaPool's static object
+**      (SchemaPool.sSchema).
+*/
+struct SchemaPool {
+  int nRef;                       /* Number of pointers to this object */
+  int nDelete;                    /* Schema objects deleted by ReleaseAll() */
+  u64 cksum;                      /* Checksum for this Schema contents */
+  Schema *pSchema;                /* Linked list of Schema objects */
+  Schema sSchema;                 /* The single dummy schema object */
+  SchemaPool *pNext;              /* Next element in schemaPoolList */
+};
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+#ifdef SQLITE_DEBUG
+static void assert_schema_state_ok(sqlite3 *db){
+  if( IsSharedSchema(db) && db->eOpenState!=SQLITE_STATE_ZOMBIE ){
+    int i;
+    for(i=0; i<db->nDb; i++){
+      if( i!=1 ){
+        Db *pDb = &db->aDb[i];
+        Btree *pBt = pDb->pBt;
+        if( pBt==0 ) continue;
+        assert( sqlite3BtreeSchema(pBt, 0, 0)==0 );
+        assert( pDb->pSchema );
+        if( pDb->pSPool ){
+          if( DbHasProperty(db, i, DB_SchemaLoaded)==0 ){
+            assert( pDb->pSchema->tblHash.count==0 );
+            assert( pDb->pSchema==&pDb->pSPool->sSchema );
+          }else{
+            assert( pDb->pSchema!=&pDb->pSPool->sSchema );
+          }
+        }else{
+          assert( DbHasProperty(db, i, DB_SchemaLoaded)==0 );
+          assert( pDb->pSchema->tblHash.count==0 );
+          assert( pDb->pSchema!=&pDb->pSPool->sSchema );
+        }
+      }
+    }
+  }
+}
+#else
+# define assert_schema_state_ok(x)
+#endif
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+
 /*
 ** Invoke the 'collation needed' callback to request a collation sequence
 ** in the encoding enc of name zName, length nName.
@@ -523,15 +580,317 @@ void sqlite3SchemaClear(void *p){
 }

 /*
-** Find and return the schema associated with a BTree.  Create
-** a new one if necessary.
+** If this database was opened with the SQLITE_OPEN_SHARED_SCHEMA flag
+** and iDb!=1, then disconnect from the schema-pool associated with
+** database iDb. Otherwise, clear the Schema object belonging to
+** database iDb. 
+**
+** If an OOM error occurs while disconnecting from a schema-pool, 
+** the db->mallocFailed flag is set.
+*/
+void sqlite3SchemaClearOrDisconnect(sqlite3 *db, int iDb){
+  Db *pDb = &db->aDb[iDb];
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  if( IsSharedSchema(db) && iDb!=1 && pDb->pSPool ){
+    sqlite3SchemaDisconnect(db, iDb, 1);
+  }else
+#endif
+  {
+    sqlite3SchemaClear(pDb->pSchema);
+  }
+}
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+/*
+** Global linked list of SchemaPool objects. Read and write access must
+** be protected by the SQLITE_MUTEX_STATIC_MASTER mutex.
+*/
+static SchemaPool *SQLITE_WSD schemaPoolList = 0;
+
+#ifdef SQLITE_TEST
+/*
+** Return a pointer to the head of the linked list of SchemaPool objects.
+** This is used by the virtual table in file test_schemapool.c.
+*/
+SchemaPool *sqlite3SchemaPoolList(void){ return schemaPoolList; }
+#endif
+
+/*
+** Database handle db was opened with the SHARED_SCHEMA flag, and database
+** iDb is currently connected to a schema-pool. When this function is called,
+** (*pnByte) is set to nInit plus the amount of memory used to store a 
+** single instance of the Schema objects managed by the schema-pool.
+** This function adjusts (*pnByte) sot hat it is set to nInit plus
+** (nSchema/nRef) of the amount of memory used by a single Schema object,
+** where nSchema is the number of Schema objects allocated by this pool,
+** and nRef is the number of connections to the schema-pool.
+*/
+void sqlite3SchemaAdjustUsed(sqlite3 *db, int iDb, int nInit, int *pnByte){
+  SchemaPool *pSPool = db->aDb[iDb].pSPool;
+  int nSchema = 0;
+  Schema *p;
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  for(p=pSPool->pSchema; p; p=p->pNext){
+    nSchema++;
+  }
+  *pnByte = nInit + ((*pnByte - nInit) * nSchema) / pSPool->nRef;
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+}
+
+/*
+** Check that the schema of db iDb is writable (either because it is the 
+** temp db schema or because the db handle was opened without
+** SQLITE_OPEN_SHARED_SCHEMA). If so, do nothing. Otherwise, leave an 
+** error in the Parse object.
+*/
+void sqlite3SchemaWritable(Parse *pParse, int iDb){
+  if( iDb!=1 && IsSharedSchema(pParse->db) && IN_DECLARE_VTAB==0 ){
+    sqlite3ErrorMsg(pParse, "attempt to modify read-only schema");
+  }
+}
+
+/*
+** The schema object passed as the only argument was allocated using
+** sqlite3_malloc() and then populated using the usual mechanism. This
+** function frees both the Schema object and its contents.
+*/
+static void schemaDelete(Schema *pSchema){
+  sqlite3SchemaClear((void*)pSchema);
+  sqlite3_free(pSchema);
+}
+
+/*
+** When this function is called, the database connection Db must be
+** using a schema-pool (Db.pSPool!=0) and must currently have Db.pSchema
+** set to point to a populated schema object checked out from the 
+** schema-pool. It is also assumed that the STATIC_MASTER mutex is held.
+** This function returns the Schema object to the schema-pool and sets
+** Db.pSchema to point to the schema-pool's static, empty, Schema object.
+*/
+static void schemaRelease(sqlite3 *db, Db *pDb){
+  Schema *pRelease = pDb->pSchema;
+  SchemaPool *pSPool = pDb->pSPool;
+
+  assert( pDb->pSchema->iGeneration==pSPool->sSchema.iGeneration );
+  pDb->pSchema = &pSPool->sSchema;
+
+  assert( pDb->pSPool && pRelease );
+  assert( pRelease->schemaFlags & DB_SchemaLoaded );
+  assert( (pDb->pSchema->schemaFlags & DB_SchemaLoaded)==0 );
+  assert( sqlite3_mutex_held(sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER)) );
+
+  /* If the DBFLAG_FreeSchema flag is set and the database connection holds
+  ** at least one other copy of the schema being released, delete it instead
+  ** of returning it to the schema-pool.  */
+  if( db->mDbFlags & DBFLAG_FreeSchema ){
+    int i;
+    for(i=0; i<db->nDb; i++){
+      Db *p = &db->aDb[i];
+      if( p!=pDb && p->pSchema!=&pSPool->sSchema && pDb->pSPool==p->pSPool ){
+        pSPool->nDelete++;
+        schemaDelete(pRelease);
+        return;
+      }
+    }
+  }
+
+  pRelease->pNext = pDb->pSPool->pSchema;
+  pDb->pSPool->pSchema = pRelease;
+}
+
+/*
+** The schema for database iDb of database handle db, which was opened
+** with SQLITE_OPEN_SHARED_SCHEMA, has just been parsed. This function either
+** finds a matching SchemaPool object on the global list (schemaPoolList) or
+** else allocates a new one and sets the Db.pSPool variable accordingly.
+**
+** SQLITE_OK is returned if no error occurs, or an SQLite error code 
+** (SQLITE_NOMEM) otherwise.
+*/
+int sqlite3SchemaConnect(sqlite3 *db, int iDb, u64 cksum){
+  Schema *pSchema = db->aDb[iDb].pSchema;
+  SchemaPool *p;
+
+  assert( pSchema && iDb!=1 && db->aDb[iDb].pSPool==0 );
+
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+
+  /* Search for a matching SchemaPool object */
+  for(p=schemaPoolList; p; p=p->pNext){
+    if( p->cksum==cksum && p->sSchema.schema_cookie==pSchema->schema_cookie ){
+      break;
+    }
+  }
+  if( !p ){
+    /* No SchemaPool object found. Allocate a new one. */
+    p = (SchemaPool*)sqlite3_malloc(sizeof(SchemaPool));
+    if( p ){
+      memset(p, 0, sizeof(SchemaPool));
+      p->cksum = cksum;
+      p->pNext = schemaPoolList;
+      schemaPoolList = p;
+
+      p->sSchema.schema_cookie = pSchema->schema_cookie;
+      p->sSchema.iGeneration = pSchema->iGeneration;
+      p->sSchema.file_format = pSchema->file_format;
+      p->sSchema.enc = pSchema->enc;
+      p->sSchema.cache_size = pSchema->cache_size;
+    }
+  }
+
+  if( p ) p->nRef++;
+
+  /* If the SchemaPool contains one or more free schemas at the moment, 
+  ** delete one of them. */
+  if( p && p->pSchema ){
+    Schema *pDel = p->pSchema;
+    p->pSchema = pDel->pNext;
+    schemaDelete(pDel);
+  }
+
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+
+  db->aDb[iDb].pSPool = p;
+  return (p ? SQLITE_OK : SQLITE_NOMEM);
+}
+
+/*
+** If parameter iDb is 1 (the temp db), or if connection handle db was not
+** opened with the SQLITE_OPEN_SHARED_SCHEMA flag, this function is a no-op.
+** Otherwise, it disconnects from the schema-pool associated with database
+** iDb, assuming it is connected.
+**
+** If parameter bNew is true, then Db.pSchema is set to point to a new, empty,
+** Schema object obtained from sqlite3_malloc(). Or, if bNew is false, then
+** Db.pSchema is set to NULL before returning.
+**
+** If the bNew parameter is true, then this function may allocate memory. 
+** If the allocation attempt fails, then SQLITE_NOMEM is returned and the
+** schema-pool is not disconnected from. Or, if no OOM error occurs, 
+** SQLITE_OK is returned.
+*/
+int sqlite3SchemaDisconnect(sqlite3 *db, int iDb, int bNew){
+  int rc = SQLITE_OK;
+  if( IsSharedSchema(db) ){
+    Db *pDb = &db->aDb[iDb];
+    SchemaPool *pSPool = pDb->pSPool;
+    assert_schema_state_ok(db);
+    assert( pDb->pSchema );
+
+    if( pSPool==0 ){
+      assert( pDb->pVTable==0 );
+      assert( bNew==0 );
+      schemaDelete(pDb->pSchema);
+      pDb->pSchema = 0;
+    }else{
+      VTable *p;
+      VTable *pNext;
+      for(p=pDb->pVTable; p; p=pNext){
+        pNext = p->pNext;
+        sqlite3VtabUnlock(p);
+      }
+      pDb->pVTable = 0;
+      sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+      if( DbHasProperty(db, iDb, DB_SchemaLoaded) ){
+        schemaRelease(db, pDb);
+      }
+      if( bNew ){
+        Schema *pNew = sqlite3SchemaGet(db, 0);
+        if( pNew==0 ){
+          rc = SQLITE_NOMEM;
+        }else{
+          pDb->pSchema = pNew;
+        }
+      }
+      if( rc==SQLITE_OK ){
+        assert( pSPool->nRef>=1 );
+        pDb->pSPool = 0;
+        pSPool->nRef--;
+        if( pSPool->nRef<=0 ){
+          SchemaPool **pp;
+          while( pSPool->pSchema ){
+            Schema *pNext = pSPool->pSchema->pNext;
+            schemaDelete(pSPool->pSchema);
+            pSPool->pSchema = pNext;
+          }
+          for(pp=&schemaPoolList; (*pp)!=pSPool; pp=&((*pp)->pNext));
+          *pp = pSPool->pNext;
+          sqlite3_free(pSPool);
+        }
+      }
+      sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+    }
+  }
+  return rc;
+}
+
+/*
+** Extract and return a pointer to a schema object from the SchemaPool passed
+** as the only argument, if one is available. If one is not available, return
+** NULL.
+*/
+Schema *sqlite3SchemaExtract(SchemaPool *pSPool){
+  Schema *pRet = 0;
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  if( pSPool->pSchema ){
+    pRet = pSPool->pSchema;
+    pSPool->pSchema = pRet->pNext;
+    pRet->pNext = 0;
+  }
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  return pRet;
+}
+
+/*
+** Return all sharable schemas held by database handle db back to their
+** respective schema-pools. Db.pSchema variables are left pointing to
+** the static, empty, Schema object owned by each schema-pool.
+*/
+void sqlite3SchemaReleaseAll(sqlite3 *db){
+  int i;
+  assert_schema_state_ok(db);
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  for(i=0; i<db->nDb; i++){
+    if( i!=1 ){
+      Db *pDb = &db->aDb[i];
+      if( pDb->pSPool && DbHasProperty(db,i,DB_SchemaLoaded) ){
+        schemaRelease(db, pDb);
+      }
+    }
+  }
+  db->mDbFlags &= ~DBFLAG_FreeSchema;
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+}
+
+/*
+** Release any sharable schema held by connection iDb of database handle
+** db. Db.pSchema is left pointing to the static, empty, Schema object
+** owned by the schema-pool.
+*/
+void sqlite3SchemaRelease(sqlite3 *db, int iDb){
+  Db *pDb = &db->aDb[iDb];
+  assert( iDb!=1 );
+  assert_schema_state_ok(db);
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  schemaRelease(db, pDb);
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+}
+
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+
+/*
+** In most cases, this function finds and returns the schema associated 
+** with BTree handle pBt, creating a new one if necessary. However, if
+** the database handle was opened with the SQLITE_OPEN_SHARED_SCHEMA flag
+** specified, a new, empty, Schema object in memory obtained by 
+** sqlite3_malloc() is always returned.
 */
 Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
-  Schema * p;
-  if( pBt ){
-    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
+  Schema *p;
+  if( pBt && IsSharedSchema(db)==0 ){
+    p = (Schema*)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
  }else{
-    p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
+    p = (Schema*)sqlite3DbMallocZero(0, sizeof(Schema));
  }
  if( !p ){
    sqlite3OomFault(db);
@@ -1214,6 +1214,17 @@ static void disconnectAllVtab(sqlite3 *db){
        if( IsVirtual(pTab) ) sqlite3VtabDisconnect(db, pTab);
      }
    }
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    if( IsSharedSchema(db) && i!=1 ){
+      VTable *pVTable;
+      VTable *pNext;
+      for(pVTable=db->aDb[i].pVTable; pVTable; pVTable=pNext){
+        pNext = pVTable->pNext;
+        sqlite3VtabUnlock(pVTable);
+      }
+      db->aDb[i].pVTable = 0;
+    }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  }
  for(p=sqliteHashFirst(&db->aModule); p; p=sqliteHashNext(p)){
    Module *pMod = (Module *)sqliteHashData(p);
@@ -1390,6 +1401,7 @@ void sqlite3LeaveMutexAndCloseZombie(sqlite3 *db){
      sqlite3BtreeClose(pDb->pBt);
      pDb->pBt = 0;
      if( j!=1 ){
+        (void)sqlite3SchemaDisconnect(db, j, 0);
        pDb->pSchema = 0;
      }
    }
@@ -3962,7 +3974,7 @@ int sqlite3_table_column_metadata(
  int *pPrimaryKey,           /* OUTPUT: True if column part of PK */
  int *pAutoinc               /* OUTPUT: True if column is auto-increment */
 ){
-  int rc;
+  int rc = SQLITE_OK;
  char *zErrMsg = 0;
  Table *pTab = 0;
  Column *pCol = 0;
@@ -3972,7 +3984,7 @@ int sqlite3_table_column_metadata(
  int notnull = 0;
  int primarykey = 0;
  int autoinc = 0;
-
+  int bUnlock;

 #ifdef SQLITE_ENABLE_API_ARMOR
  if( !sqlite3SafetyCheckOk(db) || zTableName==0 ){
@@ -3982,14 +3994,29 @@ int sqlite3_table_column_metadata(

  /* Ensure the database schema has been loaded */
  sqlite3_mutex_enter(db->mutex);
+  bUnlock = sqlite3LockReusableSchema(db);
  sqlite3BtreeEnterAll(db);
-  rc = sqlite3Init(db, &zErrMsg);
-  if( SQLITE_OK!=rc ){
-    goto error_out;
+  if( IsSharedSchema(db)==0 ){
+    rc = sqlite3Init(db, &zErrMsg);
  }

  /* Locate the table in question */
-  pTab = sqlite3FindTable(db, zTableName, zDbName);
+  if( rc==SQLITE_OK ){
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    Parse sParse;                   /* Fake Parse object for FindTable */
+    Parse *pSaved = db->pParse;
+    memset(&sParse, 0, sizeof(sParse));
+    db->pParse = &sParse;
+#endif
+    pTab = sqlite3FindTable(db, zTableName, zDbName);
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    sqlite3_free(sParse.zErrMsg);
+    rc = sParse.rc;
+    db->pParse = pSaved;
+#endif
+  }
+  if( SQLITE_OK!=rc ) goto error_out;
+
  if( !pTab || IsView(pTab) ){
    pTab = 0;
    goto error_out;
@@ -4059,6 +4086,7 @@ error_out:
  sqlite3ErrorWithMsg(db, rc, (zErrMsg?"%s":0), zErrMsg);
  sqlite3DbFree(db, zErrMsg);
  rc = sqlite3ApiExit(db, rc);
+  sqlite3UnlockReusableSchema(db, bUnlock);
  sqlite3_mutex_leave(db->mutex);
  return rc;
 }
@@ -5311,7 +5311,7 @@ static int winOpen(

  int rc = SQLITE_OK;            /* Function Return Code */
 #if !defined(NDEBUG) || SQLITE_OS_WINCE
-  int eType = flags&0x0FFF00;  /* Type of file to open */
+  int eType = flags&0x0FFF00;    /* Type of file to open */
 #endif

  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
@@ -5080,6 +5080,115 @@ sqlite3_file *sqlite3_database_file_object(const char *zName){
 }


+#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
+/*
+** This is used by a read-only database connection in cases where there
+** is a hot journal which cannot be rolled back, but the hot journal was
+** created by an aborted "PRAGMA journal_mode = wal" statement. In this
+** case we can proceed, but must set bytes 18 and 19 of page 1 of the
+** db file to indicate that this is not a wal mode database.
+*/
+static int getPageOneNoWal(
+  Pager *pPager,      /* The pager open on the database file */
+  Pgno pgno,          /* Page number to fetch */
+  DbPage **ppPage,    /* Write a pointer to the page here */
+  int flags           /* PAGER_GET_XXX flags */
+){
+  int rc = SQLITE_OK;
+
+  assert( pgno==1 );
+  assert( pPager->readOnly );
+  assert( !isOpen(pPager->jfd) );
+
+  rc = getPageNormal(pPager, pgno, ppPage, flags);
+  if( rc==SQLITE_OK ){
+    int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
+    u8 *aPg = (u8*)(*ppPage)->pData;
+    u8 aHdr[28];
+    rc = sqlite3OsOpen(pPager->pVfs, pPager->zJournal, pPager->jfd, f, &f);
+    if( rc==SQLITE_OK ){
+      rc = sqlite3OsRead(pPager->jfd, (void*)aHdr, sizeof(aHdr), 0);
+    }
+    if( rc==SQLITE_OK ){
+      u32 off = sqlite3Get4byte(&aHdr[20]);
+      rc = sqlite3OsRead(pPager->jfd, (void*)aPg, pPager->pageSize, off+4);
+    }
+    sqlite3OsClose(pPager->jfd);
+  }
+  setGetterMethod(pPager);
+  return rc;
+}
+#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
+
+/*
+** This function is called after a potentially hot journal has been opened
+** to inspect its contents and determine whether or not it really is a
+** hot journal. The journal is not a hot journal in two cases:
+**
+**   * The first byte of the journal is 0x00, or, 
+**
+**   * The connection is opened read-only, the journal consist of page 1
+**     of the db only, and the contents of page 1 differs from the contents
+**     of the db only in bytes 18 and 19 (the wal mode setting).
+**
+** If the journal is not hot, then output variable (*pbHot) is set to 0
+** before this function returns. Otherwise, if the journal is hot, (*pbHot)
+** is set to 1.
+*/
+static int checkHotJournal(Pager *pPager, int *pbHot){
+  char aHdr[28];
+  int rc = SQLITE_OK;
+
+  *pbHot = 1;
+  rc = sqlite3OsRead(pPager->jfd, (void *)aHdr, sizeof(aHdr), 0);
+  if( rc==SQLITE_OK ){
+    if( aHdr[0]==0 ){
+      *pbHot = 0;
+    }
+#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
+    else if( pPager->readOnly ){
+      u32 nPg = sqlite3Get4byte(&aHdr[8]);
+      u32 off = sqlite3Get4byte(&aHdr[20]);
+      u32 pgsz = sqlite3Get4byte(&aHdr[24]);
+
+      if( nPg==0xFFFFFFFF ){
+        i64 sz = 0;
+        rc = sqlite3OsFileSize(pPager->jfd, &sz);
+        nPg = ((sz-off) / pgsz);
+      }
+      if( nPg==1 ){
+        u8 *a1 = 0;
+        a1 = sqlite3_malloc(pgsz*2);
+        if( a1==0 ){
+          rc = SQLITE_NOMEM_BKPT;
+        }else{
+          u8 *a2 = &a1[pgsz];
+          rc = sqlite3OsRead(pPager->jfd, a1, pgsz, off+4);
+          if( rc==SQLITE_OK ){
+            rc = sqlite3OsRead(pPager->fd, a2, pgsz, 0);
+            memcpy(&a2[18], &a1[18], 2);
+            memcpy(&a2[24], &a1[24], 4);
+            memcpy(&a2[92], &a1[92], 8);
+#ifdef SQLITE_ENABLE_ZIPVFS
+            memcpy(&a2[176], &a1[176], 4);
+#endif
+          }
+          if( rc==SQLITE_OK && memcmp(a1, a2, pgsz)==0 ){
+            *pbHot = 0;
+            pPager->xGet = getPageOneNoWal;
+          }
+          sqlite3_free(a1);
+        }
+      }
+    }
+#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
+  }
+  if( rc==SQLITE_IOERR_SHORT_READ ){
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
 /*
 ** This function is called after transitioning from PAGER_UNLOCK to
 ** PAGER_SHARED state. It tests if there is a hot journal present in
@@ -5174,15 +5283,10 @@ static int hasHotJournal(Pager *pPager, int *pExists){
            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
          }
          if( rc==SQLITE_OK ){
-            u8 first = 0;
-            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
-            if( rc==SQLITE_IOERR_SHORT_READ ){
-              rc = SQLITE_OK;
-            }
+            rc = checkHotJournal(pPager, pExists);
            if( !jrnlOpen ){
              sqlite3OsClose(pPager->jfd);
            }
-            *pExists = (first!=0);
          }else if( rc==SQLITE_CANTOPEN ){
            /* If we cannot open the rollback journal file in order to see if
            ** it has a zero header, that might be due to an I/O error, or
@@ -5433,6 +5537,10 @@ int sqlite3PagerSharedLock(Pager *pPager){
    assert( !MEMDB );
    pager_unlock(pPager);
    assert( pPager->eState==PAGER_OPEN );
+#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
+    testcase( pPager->xGet==getPageOneNoWal );
+    setGetterMethod(pPager);
+#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
  }else{
    pPager->eState = PAGER_READER;
    pPager->hasHeldSharedLock = 1;
@@ -5700,7 +5808,6 @@ static int getPageError(
  return pPager->errCode;
 }

-
 /* Dispatch all page fetch requests to the appropriate getter method.
 */
 int sqlite3PagerGet(
@@ -7401,6 +7508,15 @@ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
        assert( state==PAGER_OPEN || state==PAGER_READER );
        if( state==PAGER_OPEN ){
          rc = sqlite3PagerSharedLock(pPager);
+
+#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
+          /* If this is a read-only connection, and there is a hot-journal
+          ** created by "PRAGMA journal_mode = wal" in the file-system, then
+          ** the Pager.xGet method may have been set to getPageOneNoWal. Call
+          ** setGetterMethod() here to ensure it is set properly.  */
+          testcase( pPager->xGet==getPageOneNoWal );
+          setGetterMethod(pPager);
+#endif /* SQLITE_ENABLE_READONLY_WALJOURNAL */
        }
        if( pPager->eState==PAGER_READER ){
          assert( rc==SQLITE_OK );
@@ -504,7 +504,13 @@ void sqlite3Pragma(

  /* Make sure the database schema is loaded if the pragma requires that */
  if( (pPragma->mPragFlg & PragFlg_NeedSchema)!=0 ){
-    if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    if( IsSharedSchema(db) && (zDb || (pPragma->mPragFlg & PragFlg_OneSchema)) ){
+      assert( iDb>=0 && iDb<db->nDb );
+      pParse->rc = sqlite3SchemaLoad(db, iDb, 0, &pParse->zErrMsg);
+      if( pParse->rc ) goto pragma_out;
+    }else{
+      if( sqlite3ReadSchema(pParse) ) goto pragma_out;
+    }
  }

  /* Register the result column names for pragmas that return results */
@@ -2294,9 +2300,10 @@ void sqlite3Pragma(
  ** applications for any purpose.
  */
  case PragTyp_HEADER_VALUE: {
-    int iCookie = pPragma->iArg;  /* Which cookie to read or write */
+    int iCookie;                  /* Which cookie to read or write */
+    iCookie = pPragma->iArg & PRAGMA_HEADER_VALUE_MASK;     
    sqlite3VdbeUsesBtree(v, iDb);
-    if( zRight && (pPragma->mPragFlg & PragFlg_ReadOnly)==0 ){
+    if( zRight && (pPragma->iArg & PRAGMA_HEADER_VALUE_READONLY)==0 ){
      /* Write the specified cookie value */
      static const VdbeOpList setCookie[] = {
        { OP_Transaction,    0,  1,  0},    /* 0 */
@@ -43,6 +43,11 @@ static void corruptSchema(
    pData->rc = SQLITE_ERROR;
  }else if( db->flags & SQLITE_WriteSchema ){
    pData->rc = SQLITE_CORRUPT_BKPT;
+  }else if( IsSharedSchema(db) 
+         && 0==sqlite3StrNICmp(zExtra, "malformed database schema", 17)
+  ){
+    pData->rc = SQLITE_CORRUPT_BKPT;
+    *pData->pzErrMsg = sqlite3DbStrDup(db, zExtra);
  }else{
    char *z;
    const char *zObj = azObj[1] ? azObj[1] : "?";
@@ -53,6 +58,28 @@ static void corruptSchema(
  }
 }

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+/*
+** Update the Schema.cksum checksum to account for the database object
+** specified by the three arguments following the first.
+*/
+static void schemaUpdateChecksum(
+  InitData *pData,                /* Schema parse context */
+  const char *zName,              /* Name of new database object */
+  const char *zRoot,              /* Root page of new database object */
+  const char *zSql                /* SQL used to create new database object */
+){
+  int i;
+  u64 cksum = pData->cksum;
+  if( zName ){
+    for(i=0; zName[i]; i++) cksum += (cksum<<3) + zName[i];
+  }
+  if( zRoot ) for(i=0; zRoot[i]; i++) cksum += (cksum<<3) + zRoot[i];
+  if( zSql ) for(i=0; zSql[i]; i++) cksum += (cksum<<3) + zSql[i];
+  pData->cksum = cksum;
+}
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+
 /*
 ** Check to see if any sibling index (another index on the same table)
 ** of pIndex has the same root page number, and if it does, return true.
@@ -76,6 +103,15 @@ static int sqlite3Prepare(
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pzTail       /* OUT: End of parsed string */
 );
+static int sqlite3LockAndPrepare(
+  sqlite3 *db,              /* Database handle. */
+  const char *zSql,         /* UTF-8 encoded SQL statement. */
+  int nBytes,               /* Length of zSql in bytes. */
+  u32 prepFlags,            /* Zero or more SQLITE_PREPARE_* flags */
+  Vdbe *pReprepare,         /* VM being reprepared */
+  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
+  const char **pzTail       /* OUT: End of parsed string */
+);


 /*
@@ -141,7 +177,11 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
    db->init.orphanTrigger = 0;
    db->init.azInit = (const char**)argv;
    pStmt = 0;
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    TESTONLY(rcp = ) sqlite3LockAndPrepare(db, argv[4], -1, 0, 0, &pStmt, 0);
+#else
    TESTONLY(rcp = ) sqlite3Prepare(db, argv[4], -1, 0, 0, &pStmt, 0);
+#endif
    rc = db->errCode;
    assert( (rc&0xFF)==(rcp&0xFF) );
    db->init.iDb = saved_iDb;
@@ -153,7 +193,11 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
        if( rc > pData->rc ) pData->rc = rc;
        if( rc==SQLITE_NOMEM ){
          sqlite3OomFault(db);
-        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
+        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+               && (rc&0xFF)!=SQLITE_IOERR
+#endif
+        ){
          corruptSchema(pData, argv, sqlite3_errmsg(db));
        }
      }
@@ -184,6 +228,12 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
      }
    }
  }
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  if( IsSharedSchema(db) && iDb!=1 ){
+    schemaUpdateChecksum(pData, argv[0], argv[1], argv[2]);
+  }
+#endif
  return 0;
 }

@@ -211,10 +261,28 @@ int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg, u32 mFlags){

  assert( (db->mDbFlags & DBFLAG_SchemaKnownOk)==0 );
  assert( iDb>=0 && iDb<db->nDb );
-  assert( db->aDb[iDb].pSchema );
+  assert( db->aDb[iDb].pSchema || (IsSharedSchema(db) && iDb!=1) );
  assert( sqlite3_mutex_held(db->mutex) );
  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );

+  pDb = &db->aDb[iDb];
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  assert( pDb->pSPool==0 || IsSharedSchema(db) );
+  if( pDb->pSPool ){
+    /* See if there is a free schema object in the schema-pool. If not,
+    ** disconnect from said schema pool and continue. This function will
+    ** connect to a (possibly different) schema-pool before returning. */
+    Schema *pNew = sqlite3SchemaExtract(pDb->pSPool);
+    if( pNew ){
+      pDb->pSchema = pNew;
+      return SQLITE_OK;
+    }
+    rc = sqlite3SchemaDisconnect(db, iDb, 1);
+    if( rc!=SQLITE_OK ) goto error_out;
+    assert( pDb->pSchema && pDb->pSPool==0 );
+  }
+#endif
+
  db->init.busy = 1;

  /* Construct the in-memory representation schema tables (sqlite_schema or
@@ -235,6 +303,7 @@ int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg, u32 mFlags){
  initData.pzErrMsg = pzErrMsg;
  initData.mInitFlags = mFlags;
  initData.nInitRow = 0;
+  initData.cksum = 0;
  initData.mxPage = 0;
  sqlite3InitCallback(&initData, 5, (char **)azArg, 0);
  db->mDbFlags &= mask;
@@ -245,7 +314,6 @@ int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg, u32 mFlags){

  /* Create a cursor to hold the database open
  */
-  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    assert( iDb==1 );
    DbSetProperty(db, 1, DB_SchemaLoaded);
@@ -404,6 +472,10 @@ int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg, u32 mFlags){
    rc = SQLITE_OK;
  }

+  if( rc==SQLITE_OK && iDb!=1 && IsSharedSchema(db) ){
+    rc = sqlite3SchemaConnect(db, iDb, initData.cksum);
+  }
+
  /* Jump here for an error that occurs after successfully allocating
  ** curMain and calling sqlite3BtreeEnter(). For an error that occurs
  ** before that point, jump to error_out.
@@ -425,6 +497,35 @@ error_out:
  return rc;
 }

+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+/*
+** If this is a SHARED_SCHEMA connection and the DBFLAG_SchemaInUse flag
+** is not currently set, set it and return non-zero. Otherwise, return 0.
+*/
+int sqlite3LockReusableSchema(sqlite3 *db){
+  if( IsSharedSchema(db) && (db->mDbFlags & DBFLAG_SchemaInuse)==0 ){
+    db->mDbFlags |= DBFLAG_SchemaInuse;
+    return 1;
+  }
+  return 0;
+}
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+/*
+** This function is a no-op for non-SHARED_SCHEMA connections, or if bRelease
+** is zero. Otherwise, clear the DBFLAG_SchemaInuse flag and release all
+** schema references currently held.
+*/
+void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease){
+  if( bRelease ){
+    db->mDbFlags &= ~DBFLAG_SchemaInuse;
+    sqlite3SchemaReleaseAll(db);
+  }
+}
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+
 /*
 ** Initialize all database files - the main database file, the file
 ** used to store temporary tables, and any additional database files
@@ -435,8 +536,12 @@ error_out:
 ** bit is set in the flags field of the Db structure. 
 */
 int sqlite3Init(sqlite3 *db, char **pzErrMsg){
-  int i, rc;
+  int rc = SQLITE_OK;
+  int bReleaseSchema;
+  int i;
  int commit_internal = !(db->mDbFlags&DBFLAG_SchemaChange);
+
+  bReleaseSchema = sqlite3LockReusableSchema(db);
  
  assert( sqlite3_mutex_held(db->mutex) );
  assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
@@ -446,20 +551,19 @@ int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  /* Do the main schema first */
  if( !DbHasProperty(db, 0, DB_SchemaLoaded) ){
    rc = sqlite3InitOne(db, 0, pzErrMsg, 0);
-    if( rc ) return rc;
  }
  /* All other schemas after the main schema. The "temp" schema must be last */
-  for(i=db->nDb-1; i>0; i--){
+  for(i=db->nDb-1; rc==SQLITE_OK && i>0; i--){
    assert( i==1 || sqlite3BtreeHoldsMutex(db->aDb[i].pBt) );
    if( !DbHasProperty(db, i, DB_SchemaLoaded) ){
      rc = sqlite3InitOne(db, i, pzErrMsg, 0);
-      if( rc ) return rc;
    }
  }
-  if( commit_internal ){
+  if( rc==SQLITE_OK && commit_internal ){
    sqlite3CommitInternalChanges(db);
  }
-  return SQLITE_OK;
+  sqlite3UnlockReusableSchema(db, bReleaseSchema);
+  return rc;
 }

 /*
@@ -471,11 +575,12 @@ int sqlite3ReadSchema(Parse *pParse){
  sqlite3 *db = pParse->db;
  assert( sqlite3_mutex_held(db->mutex) );
  if( !db->init.busy ){
+    db->mDbFlags |= DBFLAG_FreeSchema;      /* For sharable-schema mode */
    rc = sqlite3Init(db, &pParse->zErrMsg);
    if( rc!=SQLITE_OK ){
      pParse->rc = rc;
      pParse->nErr++;
-    }else if( db->noSharedCache ){
+    }else if( db->noSharedCache && !IsSharedSchema(db) ){
      db->mDbFlags |= DBFLAG_SchemaKnownOk;
    }
  }
@@ -501,6 +606,10 @@ static void schemaIsValid(Parse *pParse){
    Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
    if( pBt==0 ) continue;

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    if( IsSharedSchema(db) && iDb!=1 && db->aDb[iDb].pSPool==0 ) continue;
+#endif
+
    /* If there is not already a read-only (or read-write) transaction opened
    ** on the b-tree database, open one now. If a transaction is opened, it 
    ** will be closed immediately after reading the meta-value. */
@@ -843,6 +952,7 @@ static int sqlite3LockAndPrepare(
 ){
  int rc;
  int cnt = 0;
+  int bReleaseSchema = 0;

 #ifdef SQLITE_ENABLE_API_ARMOR
  if( ppStmt==0 ) return SQLITE_MISUSE_BKPT;
@@ -852,6 +962,7 @@ static int sqlite3LockAndPrepare(
    return SQLITE_MISUSE_BKPT;
  }
  sqlite3_mutex_enter(db->mutex);
+  bReleaseSchema = sqlite3LockReusableSchema(db);
  sqlite3BtreeEnterAll(db);
  do{
    /* Make multiple attempts to compile the SQL, until it either succeeds
@@ -862,7 +973,11 @@ static int sqlite3LockAndPrepare(
    if( rc==SQLITE_OK || db->mallocFailed ) break;
  }while( (rc==SQLITE_ERROR_RETRY && (cnt++)<SQLITE_MAX_PREPARE_RETRY)
       || (rc==SQLITE_SCHEMA && (sqlite3ResetOneSchema(db,-1), cnt++)==0) );
+
  sqlite3BtreeLeaveAll(db);
+
+  sqlite3UnlockReusableSchema(db, bReleaseSchema);
+
  rc = sqlite3ApiExit(db, rc);
  assert( (rc&db->errMask)==rc );
  db->busyHandler.nBusy = 0;
@@ -1528,13 +1528,14 @@ static ShellState shellState;

 /* Allowed values for ShellState.openMode
 */
-#define SHELL_OPEN_UNSPEC      0      /* No open-mode specified */
-#define SHELL_OPEN_NORMAL      1      /* Normal database file */
-#define SHELL_OPEN_APPENDVFS   2      /* Use appendvfs */
-#define SHELL_OPEN_ZIPFILE     3      /* Use the zipfile virtual table */
-#define SHELL_OPEN_READONLY    4      /* Open a normal database read-only */
-#define SHELL_OPEN_DESERIALIZE 5      /* Open using sqlite3_deserialize() */
-#define SHELL_OPEN_HEXDB       6      /* Use "dbtotxt" output as data source */
+#define SHELL_OPEN_UNSPEC       0     /* No open-mode specified */
+#define SHELL_OPEN_NORMAL       1     /* Normal database file */
+#define SHELL_OPEN_APPENDVFS    2     /* Use appendvfs */
+#define SHELL_OPEN_ZIPFILE      3     /* Use the zipfile virtual table */
+#define SHELL_OPEN_READONLY     4     /* Open a normal database read-only */
+#define SHELL_OPEN_DESERIALIZE  5     /* Open using sqlite3_deserialize() */
+#define SHELL_OPEN_HEXDB        6     /* Use "dbtotxt" output as data source */
+#define SHELL_OPEN_SHAREDSCHEMA 7     /* Open for schema reuse */

 /* Allowed values for ShellState.eTraceType
 */
@@ -2741,6 +2742,8 @@ static int shell_callback(
      char cEnd = 0;
      char c;
      int nLine = 0;
+      int isIndex;
+      int isWhere = 0;
      assert( nArg==1 );
      if( azArg[0]==0 ) break;
      if( sqlite3_strlike("CREATE VIEW%", azArg[0], 0)==0
@@ -2749,6 +2752,8 @@ static int shell_callback(
        sqlite3_fprintf(p->out, "%s;\n", azArg[0]);
        break;
      }
+      isIndex = sqlite3_strlike("CREATE INDEX%", azArg[0], 0)==0
+             || sqlite3_strlike("CREATE UNIQUE INDEX%", azArg[0], 0)==0;
      z = sqlite3_mprintf("%s", azArg[0]);
      shell_check_oom(z);
      j = 0;
@@ -2778,14 +2783,26 @@ static int shell_callback(
            nParen++;
          }else if( c==')' ){
            nParen--;
-            if( nLine>0 && nParen==0 && j>0 ){
+            if( nLine>0 && nParen==0 && j>0 && !isWhere ){
              printSchemaLineN(p->out, z, j, "\n");
              j = 0;
            }
+          }else if( (c=='w' || c=='W')
+                 && nParen==0 && isIndex
+                 && sqlite3_strnicmp("WHERE",&z[i],5)==0
+                 && !isalnum(z[i+5]) && z[i+5]!='_' ){
+            isWhere = 1;
+          }else if( isWhere && (c=='A' || c=='a')
+                 && nParen==0
+                 && sqlite3_strnicmp("AND",&z[i],3)==0
+                 && !isalnum(z[i+3]) && z[i+3]!='_' ){
+            printSchemaLineN(p->out, z, j, "\n    ");
+            j = 0;
          }
          z[j++] = c;
          if( nParen==1 && cEnd==0
           && (c=='(' || c=='\n' || (c==',' && !wsToEol(z+i+1)))
+           && !isWhere
          ){
            if( c=='\n' ) j--;
            printSchemaLineN(p->out, z, j, "\n  ");
@@ -5261,6 +5278,12 @@ static const char *(azHelp[]) = {
  "      --sha3-384            Use the sha3-384 algorithm",
  "      --sha3-512            Use the sha3-512 algorithm",
  "    Any other argument is a LIKE pattern for tables to hash",
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_ENABLE_DBPAGE_VTAB)
+  ".shared-schema CMD DB1 DB2 ...",
+  "    Commands:",
+  "       check                Determine if DB1, DB2, etc have identical schemas",
+  "       fix                  Attempt to make DB1, DB2, etc compatible",
+#endif
 #if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
  ".shell CMD ARGS...       Run CMD ARGS... in a system shell",
 #endif
@@ -5708,6 +5731,11 @@ static void open_db(ShellState *p, int openFlags){
            SQLITE_OPEN_READONLY|p->openFlags, 0);
        break;
      }
+      case SHELL_OPEN_SHAREDSCHEMA: {
+        sqlite3_open_v2(p->pAuxDb->zDbFilename, &p->db,
+          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_SHARED_SCHEMA,0);
+        break;
+      }
      case SHELL_OPEN_UNSPEC:
      case SHELL_OPEN_NORMAL: {
        sqlite3_open_v2(zDbFilename, &p->db,
@@ -8101,8 +8129,277 @@ end_ar_command:
 *******************************************************************************/
 #endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB) */

-#if SQLITE_SHELL_HAVE_RECOVER
+/*
+** If (*pRc) is not SQLITE_OK when this function is called, it is a no-op.
+** Otherwise, the SQL statement or statements in zSql are executed using
+** database connection db and the error code written to *pRc before
+** this function returns.
+*/
+static void shellExec(sqlite3 *db, int *pRc, const char *zSql){
+  int rc = *pRc;
+  if( rc==SQLITE_OK ){
+    char *zErr = 0;
+    rc = sqlite3_exec(db, zSql, 0, 0, &zErr);
+    if( rc!=SQLITE_OK ){
+      sqlite3_fprintf(stderr, "SQL error: %s\n", zErr);
+    }
+    sqlite3_free(zErr);
+    *pRc = rc;
+  }
+}

+/*
+** Like shellExec(), except that zFmt is a printf() style format string.
+*/
+static void shellExecPrintf(sqlite3 *db, int *pRc, const char *zFmt, ...){
+  char *z = 0;
+  if( *pRc==SQLITE_OK ){
+    va_list ap;
+    va_start(ap, zFmt);
+    z = sqlite3_vmprintf(zFmt, ap);
+    va_end(ap);
+    if( z==0 ){
+      *pRc = SQLITE_NOMEM;
+    }else{
+      shellExec(db, pRc, z);
+    }
+    sqlite3_free(z);
+  }
+}
+
+static int sharedSchemaFix(ShellState *pState, const char *zDb){
+  int rc = SQLITE_OK;
+  i64 iLast = 0;
+  int iCookie = 0;
+  int iAutoVacuum = 0;
+  sqlite3_stmt *pStmt = 0;
+
+  shellExecPrintf(pState->db, &rc, "ATTACH '%q' AS _shared_schema_tmp", zDb);
+  shellExecPrintf(pState->db, &rc, "PRAGMA writable_schema = 1");
+  shellExecPrintf(pState->db, &rc, "BEGIN");
+  shellPreparePrintf(pState->db, &rc, &pStmt, 
+      "SELECT max(rowid) FROM _shared_schema_tmp.sqlite_master"
+  );
+  sqlite3_step(pStmt);
+  iLast = sqlite3_column_int64(pStmt, 0);
+  shellFinalize(&rc, pStmt);
+  shellPreparePrintf(pState->db, &rc, &pStmt,
+      "INSERT INTO _shared_schema_tmp.sqlite_master SELECT "
+      "  type, name, tbl_name, ("
+      "    SELECT rootpage FROM _shared_schema_tmp.sqlite_master WHERE "
+      "      type IS o.type AND name IS o.name AND rowid<=?"
+      "  ), sql FROM main.sqlite_master AS o"
+  );
+  sqlite3_bind_int64(pStmt, 1, iLast);
+  sqlite3_step(pStmt);
+  shellFinalize(&rc, pStmt);
+
+  shellExecPrintf(pState->db, &rc,
+      "DELETE FROM _shared_schema_tmp.sqlite_master WHERE rowid<=%lld",
+      iLast
+  );
+  shellExecPrintf(pState->db, &rc, "COMMIT");
+  sqlite3_exec(pState->db, "PRAGMA writable_schema = 0", 0, 0, 0);
+
+  /* Copy the auto-vacuum setting from main to the target db */
+  shellPreparePrintf(pState->db, &rc, &pStmt, "PRAGMA main.auto_vacuum");
+  sqlite3_step(pStmt);
+  iAutoVacuum = sqlite3_column_int(pStmt, 0);
+  shellFinalize(&rc, pStmt);
+  shellExecPrintf(pState->db, &rc, 
+      "PRAGMA _shared_schema_tmp.auto_vacuum = %d", iAutoVacuum
+  );
+
+  /* Vacuum the db in order to standardize the rootpage numbers. */
+  shellExecPrintf(pState->db, &rc, "VACUUM _shared_schema_tmp");
+
+  /* Set the schema-cookie value to the same as database "main" */
+  shellPreparePrintf(pState->db, &rc, &pStmt, "PRAGMA main.schema_version");
+  sqlite3_step(pStmt);
+  iCookie = sqlite3_column_int(pStmt, 0);
+  shellFinalize(&rc, pStmt);
+  shellExecPrintf(pState->db, &rc, 
+      "PRAGMA _shared_schema_tmp.schema_version = %d", iCookie
+  );
+
+  sqlite3_exec(pState->db, "DETACH _shared_schema_tmp", 0, 0, 0);
+  return rc;
+}
+
+static int sharedSchemaCheck(ShellState *pState, const char *zDb, int *peFix){
+  int rc = SQLITE_OK;
+  int bFailed = 0;
+  sqlite3_stmt *pStmt = 0;
+
+  if( peFix ) *peFix = 0;
+  shellExecPrintf(pState->db, &rc, "ATTACH '%q' AS _shared_schema_tmp", zDb);
+
+  /* Check if this database has the same set of objects as the current db */
+  shellPreparePrintf(pState->db, &rc, &pStmt, 
+    "SELECT type, name FROM _shared_schema_tmp.sqlite_master AS o "
+    "WHERE NOT EXISTS ("
+    "  SELECT 1 FROM main.sqlite_master "
+    "    WHERE name IS o.name AND type IS o.type"
+    ")"
+    " UNION ALL "
+    "SELECT type, name FROM main.sqlite_master AS o "
+    "WHERE NOT EXISTS ("
+    "  SELECT 1 FROM _shared_schema_tmp.sqlite_master "
+    "    WHERE name IS o.name AND type IS o.type"
+    ")"
+  );
+  if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+    sqlite3_fprintf(pState->out, "%s is NOT compatible (objects)\n", zDb);
+    bFailed = 1;
+  }
+  shellFinalize(&rc, pStmt);
+
+  /* Check if this database has the same set of SQL statements as the 
+  ** current db. */
+  if( bFailed==0 ){
+    shellPreparePrintf(pState->db, &rc, &pStmt, 
+        "SELECT 1 FROM _shared_schema_tmp.sqlite_master AS o "
+        "WHERE sql IS NOT ("
+        "  SELECT sql FROM main.sqlite_master "
+        "    WHERE name IS o.name AND type IS o.type"
+        ")"
+    );
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      sqlite3_fprintf(pState->out, "%s is NOT compatible (SQL)\n", zDb);
+      bFailed = 1;
+    }
+    shellFinalize(&rc, pStmt);
+  }
+
+  /* Check if this database has the same set of root pages as the current 
+  ** db. */
+  if( bFailed==0 ){
+    shellPreparePrintf(pState->db, &rc, &pStmt, 
+        "SELECT 1 FROM _shared_schema_tmp.sqlite_master AS o "
+        "WHERE rootpage IS NOT ("
+        "  SELECT rootpage FROM main.sqlite_master "
+        "    WHERE name IS o.name AND type IS o.type"
+        ")"
+    );
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      if( peFix==0 ){
+        sqlite3_fprintf(pState->out, "%s is NOT compatible (root pages)\n", zDb);
+      }
+      bFailed = 1;
+      if( peFix ) *peFix = 1;
+    }
+    shellFinalize(&rc, pStmt);
+  }
+
+  if( bFailed==0 ){
+    shellPreparePrintf(pState->db, &rc, &pStmt, 
+        "SELECT 1 WHERE ("
+        "  SELECT group_concat(rootpage || '.' || name || '.' || sql, '.') "
+        "  FROM _shared_schema_tmp.sqlite_master"
+        ") IS NOT ("
+        "  SELECT group_concat(rootpage || '.' || name || '.' || sql, '.') "
+        "  FROM main.sqlite_master"
+        ")"
+    );
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      if( peFix==0 ){
+        sqlite3_fprintf(pState->out, 
+            "%s is NOT compatible (order of sqlite_master rows)\n", zDb
+        );
+      }
+      bFailed = 1;
+      if( peFix ) *peFix = 2;
+    }
+    shellFinalize(&rc, pStmt);
+  }
+
+  if( bFailed==0 ){
+    int iMain = -1;
+    int iNew = +1;
+    shellPreparePrintf(pState->db, &rc, &pStmt, 
+        "PRAGMA main.schema_version"
+    );
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      iMain = sqlite3_column_int(pStmt, 0);
+    }
+    shellFinalize(&rc, pStmt);
+    shellPreparePrintf(pState->db, &rc, &pStmt, 
+        "PRAGMA _shared_schema_tmp.schema_version"
+    );
+    if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
+      iNew = sqlite3_column_int(pStmt, 0);
+    }
+    shellFinalize(&rc, pStmt);
+    if( rc==SQLITE_OK && iMain!=iNew ){
+      if( peFix==0 ){
+        sqlite3_fprintf(pState->out, 
+            "%s is NOT compatible (schema cookie)\n", zDb
+        );
+      }
+      bFailed = 1;
+      if( peFix ) *peFix = 3;
+    }
+  }
+
+  if( rc==SQLITE_OK && bFailed==0 ){
+    sqlite3_fprintf(pState->out, "%s is compatible\n", zDb);
+  }
+
+  sqlite3_exec(pState->db, "DETACH _shared_schema_tmp", 0, 0, 0);
+  return rc;
+}
+
+/*
+** .shared-schema check|fix DB1 DB2...
+*/
+static int sharedSchemaDotCommand(
+  ShellState *pState,             /* Current shell tool state */
+  char **azArg,                   /* Array of arguments passed to dot command */
+  int nArg                        /* Number of entries in azArg[] */
+){
+  int rc = SQLITE_OK;
+  int bFix = 0;                   /* Fix databases if possible */
+  int n1;
+  int i;
+  if( nArg<3 ){
+    goto shared_schema_usage;
+  }
+
+  n1 = (int)strlen(azArg[1]);
+  if( n1>0 && n1<=3 && memcmp("fix", azArg[1], n1)==0 ){
+    bFix = 1;
+  }else if( n1==0 || n1>5 || memcmp("check", azArg[1], n1) ){
+    goto shared_schema_usage;
+  }
+
+  for(i=2; rc==SQLITE_OK && i<nArg; i++){
+    int eFix = 0;
+    rc = sharedSchemaCheck(pState, azArg[i], bFix ? &eFix : 0);
+    if( rc==SQLITE_OK && bFix && eFix ){
+      sqlite3_fprintf(pState->out, "Fixing %s... ", azArg[i]);
+      fflush(pState->out);
+      rc = sharedSchemaFix(pState, azArg[i]);
+      if( rc==SQLITE_OK ){
+        rc = sharedSchemaCheck(pState, azArg[i], &eFix);
+        if( rc==SQLITE_OK && eFix ){
+          sqlite3_fprintf(pState->out, "VACUUMing main... ");
+          fflush(pState->out);
+          rc = sqlite3_exec(pState->db, "VACUUM main", 0, 0, 0);
+          if( rc==SQLITE_OK ){
+            rc = sharedSchemaCheck(pState, azArg[i], 0);
+          }
+        }
+      }
+    }
+  }
+
+  return rc;
+ shared_schema_usage:
+  sqlite3_fprintf(stderr, "usage: .shared-schema check|fix DB1 DB2...\n");
+  return SQLITE_ERROR;
+}
+
+#if SQLITE_SHELL_HAVE_RECOVER
 /*
 ** This function is used as a callback by the recover extension. Simply
 ** print the supplied SQL statement to stdout.
@@ -11284,6 +11581,13 @@ static int do_meta_command(char *zLine, ShellState *p){
    sqlite3_free(zSql);
  }else

+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_ENABLE_DBPAGE_VTAB)
+  if( c=='s' && strncmp(azArg[0], "shared-schema", n)==0 ){
+    open_db(p, 0);
+    sharedSchemaDotCommand(p, azArg, nArg);
+  }else
+#endif
+
 #if !defined(SQLITE_NOHAVE_SYSTEM) && !defined(SQLITE_SHELL_FIDDLE)
  if( c=='s'
   && (cli_strncmp(azArg[0], "shell", n)==0
@@ -13155,6 +13459,8 @@ int SQLITE_CDECL wmain(int argc, wchar_t **wargv){
 #endif
    }else if( cli_strcmp(z,"-readonly")==0 ){
      data.openMode = SHELL_OPEN_READONLY;
+    }else if( strcmp(z,"-sharedschema")==0 ){
+      data.openMode = SHELL_OPEN_SHAREDSCHEMA;
    }else if( cli_strcmp(z,"-nofollow")==0 ){
      data.openFlags = SQLITE_OPEN_NOFOLLOW;
 #if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_HAVE_ZLIB)
@@ -13311,6 +13617,8 @@ int SQLITE_CDECL wmain(int argc, wchar_t **wargv){
 #endif
    }else if( cli_strcmp(z,"-readonly")==0 ){
      data.openMode = SHELL_OPEN_READONLY;
+    }else if( strcmp(z,"-sharedschema")==0 ){
+      data.openMode = SHELL_OPEN_SHAREDSCHEMA;
    }else if( cli_strcmp(z,"-nofollow")==0 ){
      data.openFlags |= SQLITE_OPEN_NOFOLLOW;
    }else if( cli_strcmp(z,"-ascii")==0 ){
@@ -616,10 +616,11 @@ int sqlite3_exec(
 #define SQLITE_OPEN_EXRESCODE        0x02000000  /* Extended result codes */

 /* Reserved:                         0x00F00000 */
+#define SQLITE_OPEN_SHARED_SCHEMA    0x01000000  /* Ok for sqlite3_open_v2() */
+
 /* Legacy compatibility: */
 #define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */

-
 /*
 ** CAPI3REF: Device Characteristics
 **
@@ -1321,6 +1321,7 @@ typedef struct Db Db;
 typedef struct DbClientData DbClientData;
 typedef struct DbFixer DbFixer;
 typedef struct Schema Schema;
+typedef struct SchemaPool SchemaPool;
 typedef struct Expr Expr;
 typedef struct ExprList ExprList;
 typedef struct FKey FKey;
@@ -1464,6 +1465,10 @@ struct Db {
  u8 safety_level;     /* How aggressive at syncing data to disk */
  u8 bSyncSet;         /* True if "PRAGMA synchronous=N" has been run */
  Schema *pSchema;     /* Pointer to database schema (possibly shared) */
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  SchemaPool *pSPool;  /* For REUSE_SCHEMA mode */
+  VTable *pVTable;     /* List of all VTable objects (REUSE_SCHEMA mode only) */
+#endif
 };

 /*
@@ -1495,6 +1500,9 @@ struct Schema {
  u8 enc;              /* Text encoding used by this database */
  u16 schemaFlags;     /* Flags associated with this schema */
  int cache_size;      /* Number of pages to use in the cache */
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  Schema *pNext;       /* Next Schema object SchemaPool (REUSE_SCHEMA) */
+#endif
 };

 /*
@@ -1790,6 +1798,12 @@ struct sqlite3 {
 #endif
 };

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+# define IsSharedSchema(db) (((db)->openFlags & SQLITE_OPEN_SHARED_SCHEMA)!=0)
+#else
+# define IsSharedSchema(db) 0
+#endif
+
 /*
 ** A macro to discover the encoding of a database.
 */
@@ -1876,6 +1890,9 @@ struct sqlite3 {
 #define DBFLAG_InternalFunc   0x0020  /* Allow use of internal functions */
 #define DBFLAG_EncodingFixed  0x0040  /* No longer possible to change enc. */

+#define DBFLAG_SchemaInuse    0x0080  /* Do not release sharable schemas */
+#define DBFLAG_FreeSchema     0x0100  /* Free extra shared schemas on release */
+
 /*
 ** Bits of the sqlite3.dbOptFlags field that are used by the
 ** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface to
@@ -2393,6 +2410,9 @@ struct VTable {
  u8 eVtabRisk;             /* Riskiness of allowing hacker access */
  int iSavepoint;           /* Depth of the SAVEPOINT stack */
  VTable *pNext;            /* Next in linked list (see above) */
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  char *zName;              /* Table name (REUSE_SCHEMA mode) */
+#endif
 };

 /* Allowed values for VTable.eVtabRisk
@@ -4066,6 +4086,9 @@ struct Trigger {
  Schema *pTabSchema;     /* Schema containing the table */
  TriggerStep *step_list; /* Link list of trigger program steps             */
  Trigger *pNext;         /* Next trigger associated with the table */
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  char *zTabSchema;       /* Temp triggers in IsSharedSchema() dbs only */
+#endif
 };

 /*
@@ -4205,6 +4228,7 @@ typedef struct {
  int rc;             /* Result code stored here */
  u32 mInitFlags;     /* Flags controlling error messages */
  u32 nInitRow;       /* Number of rows processed */
+  u64 cksum;          /* Schema checksum for REUSE_SCHEMA mode */
  Pgno mxPage;        /* Maximum page number.  0 for no limit. */
 } InitData;

@@ -5422,6 +5446,29 @@ void sqlite3DefaultRowEst(Index*);
 void sqlite3RegisterLikeFunctions(sqlite3*, int);
 int sqlite3IsLikeFunction(sqlite3*,Expr*,int*,char*);
 void sqlite3SchemaClear(void *);
+void sqlite3SchemaClearOrDisconnect(sqlite3*, int);
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA 
+int sqlite3SchemaConnect(sqlite3*, int, u64);
+int sqlite3SchemaDisconnect(sqlite3 *, int, int);
+Schema *sqlite3SchemaExtract(SchemaPool*);
+int sqlite3SchemaLoad(sqlite3*, int, int*, char**);
+void sqlite3SchemaReleaseAll(sqlite3*);
+void sqlite3SchemaRelease(sqlite3*, int);
+void sqlite3SchemaAdjustUsed(sqlite3*, int, int, int*);
+void sqlite3SchemaWritable(Parse*, int);
+void sqlite3UnlockReusableSchema(sqlite3 *db, int bRelease);
+int sqlite3LockReusableSchema(sqlite3 *db);
+#else
+# define sqlite3SchemaWritable(x,y)
+# define sqlite3UnlockReusableSchema(x,y) (void)(y)
+# define sqlite3LockReusableSchema(x) 0
+# define sqlite3SchemaDisconnect(x,y,z) SQLITE_OK
+# define sqlite3SchemaLoad(w,x,y,z) SQLITE_OK
+# define sqlite3SchemaRelease(y,z)
+# define sqlite3SchemaConnect(x,y,z) SQLITE_OK
+#endif
+
 Schema *sqlite3SchemaGet(sqlite3 *, Btree *);
 int sqlite3SchemaToIndex(sqlite3 *db, Schema *);
 KeyInfo *sqlite3KeyInfoAlloc(sqlite3*,int,int);
@@ -289,13 +289,26 @@ int sqlite3_db_status(
    case SQLITE_DBSTATUS_SCHEMA_USED: {
      int i;                      /* Used to iterate through schemas */
      int nByte = 0;              /* Used to accumulate return value */
+      int bReleaseSchema;

      sqlite3BtreeEnterAll(db);
+      bReleaseSchema = sqlite3LockReusableSchema(db);
      db->pnBytesFreed = &nByte;
      assert( db->lookaside.pEnd==db->lookaside.pTrueEnd );
      db->lookaside.pEnd = db->lookaside.pStart;
      for(i=0; i<db->nDb; i++){
-        Schema *pSchema = db->aDb[i].pSchema;
+        Schema *pSchema;
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+        int bUnload = 0;
+        int nUsed = nByte;
+        if( db->aDb[i].pSPool ){
+          char *zDummy = 0;
+          rc = sqlite3SchemaLoad(db, i, &bUnload, &zDummy);
+          sqlite3_free(zDummy);
+          if( rc ) break;
+        }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+        pSchema = db->aDb[i].pSchema;
        if( ALWAYS(pSchema!=0) ){
          HashElem *p;

@@ -317,7 +330,14 @@ int sqlite3_db_status(
            sqlite3DeleteTable(db, (Table *)sqliteHashData(p));
          }
        }
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+        if( db->aDb[i].pSPool ){
+          if( bUnload ) sqlite3SchemaRelease(db, i);
+          sqlite3SchemaAdjustUsed(db, i, nUsed, &nByte);
+        }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
      }
+      sqlite3UnlockReusableSchema(db, bReleaseSchema);
      db->pnBytesFreed = 0;
      db->lookaside.pEnd = db->lookaside.pTrueEnd;
      sqlite3BtreeLeaveAll(db);
@@ -3772,6 +3772,9 @@ static int sqliteCmdUsage(
    "HANDLE ?FILENAME? ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN?"
    " ?-nofollow BOOLEAN?"
    " ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN?"
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    " ?-shared-schema BOOLEAN?"
+#endif
  );
  return TCL_ERROR;
 }
@@ -3903,6 +3906,16 @@ static int SQLITE_TCLAPI DbMain(
      }else{
        flags &= ~SQLITE_OPEN_URI;
      }
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    }else if( strcmp(zArg, "-shared-schema")==0 ){
+      int b;
+      if( Tcl_GetBooleanFromObj(interp, objv[i], &b) ) return TCL_ERROR;
+      if( b ){
+        flags |= SQLITE_OPEN_SHARED_SCHEMA;
+      }else{
+        flags &= ~SQLITE_OPEN_SHARED_SCHEMA;
+      }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
    }else if( strcmp(zArg, "-translatefilename")==0 ){
      if( Tcl_GetBooleanFromObj(interp, objv[i], &bTranslateFileName) ){
        return TCL_ERROR;
@@ -569,6 +569,14 @@ Tcl_SetVar2(interp, "sqlite_options", "mergesort", "1", TCL_GLOBAL_ONLY);
  Tcl_SetVar2(interp, "sqlite_options", "progress", "1", TCL_GLOBAL_ONLY);
 #endif

+#ifdef SQLITE_ENABLE_READONLY_WALJOURNAL
+  Tcl_SetVar2(
+      interp, "sqlite_options", "readonly_waljournal", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(
+      interp, "sqlite_options", "readonly_waljournal", "0", TCL_GLOBAL_ONLY);
+#endif
+
 #ifdef SQLITE_OMIT_REINDEX
  Tcl_SetVar2(interp, "sqlite_options", "reindex", "0", TCL_GLOBAL_ONLY);
 #else
@@ -787,6 +795,13 @@ Tcl_SetVar2(interp, "sqlite_options", "mergesort", "1", TCL_GLOBAL_ONLY);
  Tcl_SetVar2(interp, "sqlite_options", "windowfunc", "1", TCL_GLOBAL_ONLY);
 #endif

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  Tcl_SetVar2(interp, "sqlite_options", "sharedschema", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "sharedschema", "0", TCL_GLOBAL_ONLY);
+#endif
+
+
 #if !defined(SQLITE_ENABLE_SETLK_TIMEOUT)
  Tcl_SetVar2(interp, "sqlite_options", "setlk_timeout", "0", TCL_GLOBAL_ONLY);
 #else
@@ -0,0 +1,281 @@
+/*
+** 2006 June 10
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** Code for testing the virtual table interfaces.  This code
+** is not included in the SQLite library.  It is used for automated
+** testing of the SQLite library.
+*/
+
+/*
+** None of this works unless we have virtual tables.
+*/
+#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_TEST)
+
+#include "tclsqlite.h"
+
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+
+#include "sqliteInt.h"
+
+/* The code in this file defines a sqlite3 virtual-table module with
+** the following schema.
+*/
+#define SCHEMAPOOL_SCHEMA \
+"CREATE TABLE x("         \
+"  cksum   INTEGER, "     \
+"  nref    INTEGER, "     \
+"  nschema INTEGER, "     \
+"  ndelete INTEGER  "     \
+")"
+
+#define SCHEMAPOOL_NFIELD 4
+
+typedef struct schemapool_vtab schemapool_vtab;
+typedef struct schemapool_cursor schemapool_cursor;
+
+/* A schema table object */
+struct schemapool_vtab {
+  sqlite3_vtab base;
+};
+
+/* A schema table cursor object */
+struct schemapool_cursor {
+  sqlite3_vtab_cursor base;
+  sqlite3_int64 *aData;
+  int iRow;
+  int nRow;
+};
+
+/*
+** Table destructor for the schema module.
+*/
+static int schemaPoolDestroy(sqlite3_vtab *pVtab){
+  sqlite3_free(pVtab);
+  return 0;
+}
+
+/*
+** Table constructor for the schema module.
+*/
+static int schemaPoolCreate(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  int rc = SQLITE_NOMEM;
+  schemapool_vtab *pVtab = sqlite3_malloc(sizeof(schemapool_vtab));
+  if( pVtab ){
+    memset(pVtab, 0, sizeof(schemapool_vtab));
+    rc = sqlite3_declare_vtab(db, SCHEMAPOOL_SCHEMA);
+    if( rc!=SQLITE_OK ){
+      sqlite3_free(pVtab);
+      pVtab = 0;
+    }
+  }
+  *ppVtab = (sqlite3_vtab *)pVtab;
+  return rc;
+}
+
+/*
+** Open a new cursor on the schema table.
+*/
+static int schemaPoolOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  int rc = SQLITE_NOMEM;
+  schemapool_cursor *pCur;
+  pCur = sqlite3_malloc(sizeof(schemapool_cursor));
+  if( pCur ){
+    memset(pCur, 0, sizeof(schemapool_cursor));
+    *ppCursor = (sqlite3_vtab_cursor*)pCur;
+    rc = SQLITE_OK;
+  }
+  return rc;
+}
+
+/*
+** Close a schema table cursor.
+*/
+static int schemaPoolClose(sqlite3_vtab_cursor *cur){
+  schemapool_cursor *pCur = (schemapool_cursor*)cur;
+  sqlite3_free(pCur->aData);
+  sqlite3_free(pCur);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve a column of data.
+*/
+static int schemaPoolColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+  schemapool_cursor *pCur = (schemapool_cursor*)cur;
+  assert( i==0 || i==1 || i==2 || i==3 );
+  sqlite3_result_int64(ctx, pCur->aData[pCur->iRow*SCHEMAPOOL_NFIELD + i]);
+  return SQLITE_OK;
+}
+
+/*
+** Retrieve the current rowid.
+*/
+static int schemaPoolRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
+  schemapool_cursor *pCur = (schemapool_cursor*)cur;
+  *pRowid = pCur->iRow + 1;
+  return SQLITE_OK;
+}
+
+static int schemaPoolEof(sqlite3_vtab_cursor *cur){
+  schemapool_cursor *pCur = (schemapool_cursor*)cur;
+  return pCur->iRow>=pCur->nRow;
+}
+
+/*
+** Advance the cursor to the next row.
+*/
+static int schemaPoolNext(sqlite3_vtab_cursor *cur){
+  schemapool_cursor *pCur = (schemapool_cursor*)cur;
+  pCur->iRow++;
+  return SQLITE_OK;
+}
+
+struct SchemaPool {
+  int nRef;                       /* Number of pointers to this object */
+  int nDelete;                    /* Schema objects deleted by ReleaseAll() */
+  u64 cksum;                      /* Checksum for this Schema contents */
+  Schema *pSchema;                /* Linked list of Schema objects */
+  Schema sSchema;                 /* The single dummy schema object */
+  SchemaPool *pNext;              /* Next element in schemaPoolList */
+};
+extern SchemaPool *sqlite3SchemaPoolList(void);
+
+/*
+** Reset a schemaPool table cursor.
+*/
+static int schemaPoolFilter(
+  sqlite3_vtab_cursor *pVtabCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  SchemaPool *pSPool;
+  schemapool_cursor *pCur = (schemapool_cursor*)pVtabCursor;
+
+  sqlite3_free(pCur->aData);
+  pCur->aData = 0;
+  pCur->nRow = 0;
+  pCur->iRow = 0;
+
+  for(pSPool = sqlite3SchemaPoolList(); pSPool; pSPool=pSPool->pNext){
+    pCur->nRow++;
+  }
+
+  if( pCur->nRow ){
+    int iRow = 0;
+    int nByte = SCHEMAPOOL_NFIELD * pCur->nRow * sizeof(i64);
+    pCur->aData = (i64*)sqlite3_malloc(nByte);
+    if( pCur->aData==0 ) return SQLITE_NOMEM;
+    for(pSPool = sqlite3SchemaPoolList(); pSPool; pSPool=pSPool->pNext){
+      Schema *p;
+      i64 nSchema = 0;
+      for(p=pSPool->pSchema; p; p=p->pNext){
+        nSchema++;
+      }
+      pCur->aData[0 + iRow*SCHEMAPOOL_NFIELD] = pSPool->cksum;
+      pCur->aData[1 + iRow*SCHEMAPOOL_NFIELD] = (i64)pSPool->nRef;
+      pCur->aData[2 + iRow*SCHEMAPOOL_NFIELD] = nSchema;
+      pCur->aData[3 + iRow*SCHEMAPOOL_NFIELD] = (i64)pSPool->nDelete;
+      iRow++;
+    }
+  }
+
+  return SQLITE_OK;
+}
+
+/*
+** Analyse the WHERE condition.
+*/
+static int schemaPoolBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+  return SQLITE_OK;
+}
+
+/*
+** A virtual table module that merely echos method calls into TCL
+** variables.
+*/
+static sqlite3_module schemaPoolModule = {
+  0,                           /* iVersion */
+  schemaPoolCreate,
+  schemaPoolCreate,
+  schemaPoolBestIndex,
+  schemaPoolDestroy,
+  schemaPoolDestroy,
+  schemaPoolOpen,              /* xOpen - open a cursor */
+  schemaPoolClose,             /* xClose - close a cursor */
+  schemaPoolFilter,            /* xFilter - configure scan constraints */
+  schemaPoolNext,              /* xNext - advance a cursor */
+  schemaPoolEof,               /* xEof */
+  schemaPoolColumn,            /* xColumn - read data */
+  schemaPoolRowid,             /* xRowid - read data */
+  0,                           /* xUpdate */
+  0,                           /* xBegin */
+  0,                           /* xSync */
+  0,                           /* xCommit */
+  0,                           /* xRollback */
+  0,                           /* xFindMethod */
+  0,                           /* xRename */
+};
+
+/*
+** Decode a pointer to an sqlite3 object.
+*/
+extern int getDbPointer(Tcl_Interp *interp, const char *zA, sqlite3 **ppDb);
+
+/*
+** Register the schema virtual table module.
+*/
+static int SQLITE_TCLAPI register_schemapool_module(
+  ClientData clientData, /* Not used */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  sqlite3 *db;
+  if( objc!=2 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  sqlite3_create_module(db, "schemapool", &schemaPoolModule, 0);
+#endif
+  return TCL_OK;
+}
+
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+#endif /* !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_TEST) */
+
+/*
+** Register commands with the TCL interpreter.
+*/
+int Sqlitetestschemapool_Init(Tcl_Interp *interp){
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  static struct {
+     char *zName;
+     Tcl_ObjCmdProc *xProc;
+     void *clientData;
+  } aObjCmd[] = {
+     { "register_schemapool_module", register_schemapool_module, 0 },
+  };
+  int i;
+  for(i=0; i<sizeof(aObjCmd)/sizeof(aObjCmd[0]); i++){
+    Tcl_CreateObjCommand(interp, aObjCmd[i].zName, 
+        aObjCmd[i].xProc, aObjCmd[i].clientData, 0);
+  }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+  return TCL_OK;
+}
@@ -68,6 +68,7 @@ const char *sqlite3TestInit(Tcl_Interp *interp){
  extern int Sqlitetest_malloc_Init(Tcl_Interp*);
  extern int Sqlitetest_mutex_Init(Tcl_Interp*);
  extern int Sqlitetestschema_Init(Tcl_Interp*);
+  extern int Sqlitetestschemapool_Init(Tcl_Interp*);
  extern int Sqlitetestsse_Init(Tcl_Interp*);
  extern int Sqlitetesttclvar_Init(Tcl_Interp*);
  extern int Sqlitetestfs_Init(Tcl_Interp*);
@@ -139,6 +140,7 @@ const char *sqlite3TestInit(Tcl_Interp *interp){
  Sqlitetest_malloc_Init(interp);
  Sqlitetest_mutex_Init(interp);
  Sqlitetestschema_Init(interp);
+  Sqlitetestschemapool_Init(interp);
  Sqlitetesttclvar_Init(interp);
  Sqlitetestfs_Init(interp);
  SqlitetestThread_Init(interp);
@@ -52,13 +52,34 @@ Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
  Trigger *pList;           /* List of triggers to return */
  HashElem *p;              /* Loop variable for TEMP triggers */

+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  char *zSchema = 0;
+  sqlite3 *db = pParse->db;
+  if( IsSharedSchema(db) ){
+    zSchema = db->aDb[sqlite3SchemaToIndex(db, pTab->pSchema)].zDbSName;
+  }
+#endif
+
  assert( pParse->disableTriggers==0 );
  pTmpSchema = pParse->db->aDb[1].pSchema;
  p = sqliteHashFirst(&pTmpSchema->trigHash);
  pList = pTab->pTrigger;
  while( p ){
    Trigger *pTrig = (Trigger *)sqliteHashData(p);
-    if( pTrig->pTabSchema==pTab->pSchema
+
+    int bSchemaMatch;
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+    if( zSchema ){
+      /* Shared-schema */
+      bSchemaMatch = (0==sqlite3StrICmp(pTrig->zTabSchema, zSchema));
+    }else
+#endif
+    {
+      /* Non-shared-schema */
+      bSchemaMatch = (pTrig->pTabSchema==pTab->pSchema);
+    }
+
+    if( bSchemaMatch
     && pTrig->table
     && 0==sqlite3StrICmp(pTrig->table, pTab->zName)
     && (pTrig->pTabSchema!=pTmpSchema || pTrig->bReturning)
@@ -68,7 +89,7 @@ Trigger *sqlite3TriggerList(Parse *pParse, Table *pTab){
    }else if( pTrig->op==TK_RETURNING ){
 #ifndef SQLITE_OMIT_VIRTUALTABLE
      assert( pParse->db->pVtabCtx==0 );
-#endif
+#endif 
      assert( pParse->bReturning );
      assert( !pParse->isCreate );
      assert( &(pParse->u1.d.pReturning->retTrig) == pTrig );
@@ -266,6 +287,12 @@ void sqlite3BeginTrigger(
  pTrigger->zName = zName;
  zName = 0;
  pTrigger->table = sqlite3DbStrDup(db, pTableName->a[0].zName);
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  if( IsSharedSchema(db) && iDb==1 ){
+    int iTabDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    pTrigger->zTabSchema = sqlite3DbStrDup(db, db->aDb[iTabDb].zDbSName);
+  }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  pTrigger->pSchema = db->aDb[iDb].pSchema;
  pTrigger->pTabSchema = pTab->pSchema;
  pTrigger->op = (u8)op;
@@ -389,7 +416,7 @@ void sqlite3FinishTrigger(
       pTrig->table, z);
    sqlite3DbFree(db, z);
    sqlite3ChangeCookie(pParse, iDb);
-    sqlite3VdbeAddParseSchemaOp(v, iDb,
+    sqlite3VdbeAddParseSchemaOp(pParse, iDb,
        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName), 0);
  }

@@ -608,6 +635,9 @@ void sqlite3DeleteTrigger(sqlite3 *db, Trigger *pTrigger){
  sqlite3DeleteTriggerStep(db, pTrigger->step_list);
  sqlite3DbFree(db, pTrigger->zName);
  sqlite3DbFree(db, pTrigger->table);
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  sqlite3DbFree(db, pTrigger->zTabSchema);
+#endif
  sqlite3ExprDelete(db, pTrigger->pWhen);
  sqlite3IdListDelete(db, pTrigger->pColumns);
  sqlite3DbFree(db, pTrigger);
@@ -680,6 +710,7 @@ void sqlite3DropTriggerPtr(Parse *pParse, Trigger *pTrigger){

  iDb = sqlite3SchemaToIndex(pParse->db, pTrigger->pSchema);
  assert( iDb>=0 && iDb<db->nDb );
+  sqlite3SchemaWritable(pParse, iDb);
  pTable = tableOfTrigger(pTrigger);
  assert( (pTable && pTable->pSchema==pTrigger->pSchema) || iDb==1 );
 #ifndef SQLITE_OMIT_AUTHORIZATION
@@ -1250,7 +1281,9 @@ static TriggerPrg *codeRowTrigger(
  int iEndTrigger = 0;        /* Label to jump to if WHEN is false */
  Parse sSubParse;            /* Parse context for sub-vdbe */

-  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+  assert( pTrigger->zName==0 || IsSharedSchema(pParse->db)
+      || pTab==tableOfTrigger(pTrigger)
+  );
  assert( pTop->pVdbe );

  /* Allocate the TriggerPrg and SubProgram objects. To ensure that they
@@ -1359,7 +1392,9 @@ static TriggerPrg *getRowTrigger(
  Parse *pRoot = sqlite3ParseToplevel(pParse);
  TriggerPrg *pPrg;

-  assert( pTrigger->zName==0 || pTab==tableOfTrigger(pTrigger) );
+  assert( pTrigger->zName==0 || IsSharedSchema(pParse->db)
+      || pTab==tableOfTrigger(pTrigger) 
+  );

  /* It may be that this trigger has already been coded (or is in the
  ** process of being coded). If this is the case, then an entry with
@@ -125,6 +125,7 @@ void sqlite3Vacuum(Parse *pParse, Token *pNm, Expr *pInto){
  }
  if( iDb!=1 ){
    int iIntoReg = 0;
+    sqlite3SchemaWritable(pParse, iDb);
    if( pInto && sqlite3ResolveSelfReference(pParse,0,0,pInto,0)==0 ){
      iIntoReg = ++pParse->nMem;
      sqlite3ExprCode(pParse, pInto, iIntoReg);
@@ -4101,13 +4101,6 @@ case OP_Transaction: {
   && pOp->p5
   && (iMeta!=pOp->p3 || pDb->pSchema->iGeneration!=pOp->p4.i)
  ){
-    /*
-    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
-    ** version is checked to ensure that the schema has not changed since the
-    ** SQL statement was prepared.
-    */
-    sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    /* If the schema-cookie from the database file matches the cookie
    ** stored with the in-memory representation of the schema, do
    ** not reload the schema from the database file.
@@ -4124,6 +4117,13 @@ case OP_Transaction: {
    if( db->aDb[pOp->p1].pSchema->schema_cookie!=iMeta ){
      sqlite3ResetOneSchema(db, pOp->p1);
    }
+    /*
+    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
+    ** version is checked to ensure that the schema has not changed since the
+    ** SQL statement was prepared.
+    */
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
    p->expired = 1;
    rc = SQLITE_SCHEMA;

@@ -245,7 +245,7 @@ VdbeOp *sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp,int iLineno);
 #else
 # define sqlite3ExplainBreakpoint(A,B) /*no-op*/
 #endif
-void sqlite3VdbeAddParseSchemaOp(Vdbe*, int, char*, u16);
+void sqlite3VdbeAddParseSchemaOp(Parse*,int,char*,u16);
 void sqlite3VdbeChangeOpcode(Vdbe*, int addr, u8);
 void sqlite3VdbeChangeP1(Vdbe*, int addr, int P1);
 void sqlite3VdbeChangeP2(Vdbe*, int addr, int P2);
@@ -561,8 +561,10 @@ void sqlite3VdbeExplainPop(Parse *pParse){
 ** The zWhere string must have been obtained from sqlite3_malloc().
 ** This routine will take ownership of the allocated memory.
 */
-void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere, u16 p5){
+void sqlite3VdbeAddParseSchemaOp(Parse *pParse, int iDb, char *zWhere, u16 p5){
+  Vdbe *p = pParse->pVdbe;
  int j;
+  sqlite3SchemaWritable(pParse, iDb);
  sqlite3VdbeAddOp4(p, OP_ParseSchema, iDb, 0, 0, zWhere, P4_DYNAMIC);
  sqlite3VdbeChangeP5(p, p5);
  for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
@@ -134,6 +134,7 @@ int sqlite3_blob_open(
  Table *pTab;
  Incrblob *pBlob = 0;
  Parse sParse;
+  int bUnlock;            /* True to unlock reusable schemas before returning */

 #ifdef SQLITE_ENABLE_API_ARMOR
  if( ppBlob==0 ){
@@ -150,6 +151,7 @@ int sqlite3_blob_open(

  sqlite3_mutex_enter(db->mutex);

+  bUnlock = sqlite3LockReusableSchema(db);
  pBlob = (Incrblob *)sqlite3DbMallocZero(db, sizeof(Incrblob));
  while(1){
    sqlite3ParseObjectInit(&sParse,db);
@@ -336,6 +338,7 @@ int sqlite3_blob_open(
  }

 blob_open_out:
+  sqlite3UnlockReusableSchema(db, bUnlock);
  if( rc==SQLITE_OK && db->mallocFailed==0 ){
    *ppBlob = (sqlite3_blob *)pBlob;
  }else{
@@ -192,6 +192,24 @@ void sqlite3VtabLock(VTable *pVTab){
 VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
  VTable *pVtab;
  assert( IsVirtual(pTab) );
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  if( IsSharedSchema(db) ){
+    int iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
+    if( iDb!=1 ){
+      VTable **pp;
+      for(pp=&db->aDb[iDb].pVTable; *pp; pp=&(*pp)->pNext){
+        if( sqlite3StrICmp(pTab->zName, (*pp)->zName)==0 ) break;
+      }
+      pVtab = *pp;
+      if( pVtab && pTab->nCol<=0 ){
+        *pp = pVtab->pNext;
+        sqlite3VtabUnlock(pVtab);
+        pVtab = 0;
+      }
+      return pVtab;
+    }
+  }
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
  for(pVtab=pTab->u.vtab.p; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
  return pVtab;
 }
@@ -500,7 +518,7 @@ void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){

    sqlite3VdbeAddOp0(v, OP_Expire);
    zWhere = sqlite3MPrintf(db, "name=%Q AND sql=%Q", pTab->zName, zStmt);
-    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere, 0);
+    sqlite3VdbeAddParseSchemaOp(pParse, iDb, zWhere, 0);
    sqlite3DbFree(db, zStmt);

    iReg = ++pParse->nMem;
@@ -570,6 +588,7 @@ static int vtabCallConstructor(
  char *zModuleName;
  int iDb;
  VtabCtx *pCtx;
+  int nByte;                      /* Bytes of space to allocate */

  assert( IsVirtual(pTab) );
  azArg = (const char *const*)pTab->u.vtab.azArg;
@@ -589,7 +608,11 @@ static int vtabCallConstructor(
    return SQLITE_NOMEM_BKPT;
  }

-  pVTable = sqlite3MallocZero(sizeof(VTable));
+  nByte = sizeof(VTable);
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  nByte += sqlite3Strlen30(pTab->zName) + 1;
+#endif
+  pVTable = (VTable*)sqlite3MallocZero(nByte);
  if( !pVTable ){
    sqlite3OomFault(db);
    sqlite3DbFree(db, zModuleName);
@@ -597,6 +620,10 @@ static int vtabCallConstructor(
  }
  pVTable->db = db;
  pVTable->pMod = pMod;
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+  pVTable->zName = (char*)&pVTable[1];
+  memcpy(pVTable->zName, pTab->zName, nByte-sizeof(VTable));
+#endif
  pVTable->eVtabRisk = SQLITE_VTABRISK_Normal;

  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
@@ -643,12 +670,23 @@ static int vtabCallConstructor(
      int iCol;
      u16 oooHidden = 0;
      /* If everything went according to plan, link the new VTable structure
-      ** into the linked list headed by pTab->u.vtab.p. Then loop through the
-      ** columns of the table to see if any of them contain the token "hidden".
-      ** If so, set the Column COLFLAG_HIDDEN flag and remove the token from
-      ** the type string.  */
-      pVTable->pNext = pTab->u.vtab.p;
-      pTab->u.vtab.p = pVTable;
+      ** into the linked list headed by pTab->u.vtab.p. Or, if this is a
+      ** reusable schema, into the linked list headed by Db.pVTable.
+      **
+      ** Then loop through the columns of the table to see if any of them
+      ** contain the token "hidden". If so, set the Column COLFLAG_HIDDEN flag
+      ** and remove the token from the type string.  */
+#ifdef SQLITE_ENABLE_SHARED_SCHEMA
+      if( IsSharedSchema(db) && iDb!=1 ){
+        pVTable->pNext = db->aDb[iDb].pVTable;
+        db->aDb[iDb].pVTable = pVTable;
+      }else
+#endif /* ifdef SQLITE_ENABLE_SHARED_SCHEMA */
+      {
+        assert( IsVirtual(pTab) );
+        pVTable->pNext = pTab->u.vtab.p;
+        pTab->u.vtab.p = pVTable;
+      }

      for(iCol=0; iCol<pTab->nCol; iCol++){
        char *zType = sqlite3ColumnType(&pTab->aCol[iCol], "");
@@ -703,6 +741,7 @@ int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
  assert( pTab );
  assert( IsVirtual(pTab) );
  if( sqlite3GetVTable(db, pTab) ){
+    assert( !IsVirtual(pTab) || pTab->nCol>0 );
    return SQLITE_OK;
  }

@@ -1679,7 +1679,7 @@ static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
      sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
    }
  }
-  if( pTab->u.vtab.p->bAllSchemas ){
+  if( pTab->u.vtab.p && pTab->u.vtab.p->bAllSchemas ){
    sqlite3VtabUsesAllSchemas(pParse);
  }
  sqlite3_free(pVtab->zErrMsg);
@@ -16,6 +16,7 @@

 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
+set testprefix nolock

 unset -nocomplain tvfs_calls
 proc tvfs_reset {} {
@@ -217,4 +218,31 @@ if {[permutation]!="inmemory_journal"} {
  } {1 {unable to open database file}}
 }

+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 5.0 {
+  CREATE TABLE t1(x, y);
+  CREATE TABLE t2(x, y);
+  INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
+  INSERT INTO t2 VALUES(1, 2), (3, 4), (5, 6);
+  PRAGMA cache_size = 0;
+  BEGIN;
+    INSERT INTO t1 VALUES(7, 8);
+    INSERT INTO t2 VALUES(7, 8);
+}
+
+do_test 5.1 {
+  forcecopy test.db test.db2
+  forcecopy test.db-journal test.db2-journal
+  sqlite3 db2 file:test.db2?immutable=0 -uri 1 -readonly 1
+
+  list [catch {
+    db2 eval {
+      SELECT * FROM t1;
+      SELECT * FROM t2;
+    }
+  } msg] $msg
+} {1 {attempt to write a readonly database}}
+
 finish_test
+
@@ -0,0 +1,121 @@
+# 2024 October 30
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+# Test that readonly database connections may ignore a hot journal 
+# created by an aborted "PRAGMA journal_mode = wal" statement.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+ifcapable !readonly_waljournal {
+  finish_test
+  return
+}
+
+set ::testprefix readonly2
+
+testvfs tvfs -default 1
+tvfs script at_vfs_callback
+tvfs filter {xDelete}
+
+set ::delete_shall_fail 0
+proc at_vfs_callback {method file z args} {
+  if {$::delete_shall_fail} {
+    return "SQLITE_IOERR"
+  }
+  return "SQLITE_OK"
+}
+
+reset_db
+do_execsql_test 1.0 {
+  BEGIN;
+    CREATE TABLE t1(a, b);
+    INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
+  COMMIT;
+}
+
+set ::delete_shall_fail 1
+do_catchsql_test 1.1 {
+  PRAGMA journal_mode = wal;
+} {1 {disk I/O error}}
+
+do_test 1.2 {
+  file exists test.db-journal
+} 1
+
+do_test 1.3 {
+  sqlite3 db2 test.db -readonly 1
+  db2 eval {
+    SELECT * FROM t1
+  }
+} {1 2 3 4 5 6}
+
+do_test 1.4 {
+  file exists test.db-journal
+} 1
+
+set ::delete_shall_fail 0
+do_execsql_test 1.5 {
+  SELECT * FROM t1
+} {1 2 3 4 5 6}
+
+set ::delete_shall_fail 1
+do_catchsql_test 1.6 {
+  PRAGMA user_version = 444;
+} {1 {disk I/O error}}
+ 
+do_test 1.7 {
+  file exists test.db-journal
+} 1
+
+do_test 1.8 {
+  list [catch { db2 eval { SELECT * FROM t1 } } msg] $msg
+} {1 {attempt to write a readonly database}}
+
+do_test 1.9 {
+  file exists test.db-journal
+} 1
+
+set ::delete_shall_fail 0
+do_execsql_test 1.10 {
+  SELECT * FROM t1
+} {1 2 3 4 5 6}
+
+#---------------------------------------------------------
+reset_db
+
+do_execsql_test 2.1 {
+  CREATE TABLE t1(a, b);
+  INSERT INTO t1 VALUES('abc', 'def');
+}
+
+set ::delete_shall_fail 1
+do_catchsql_test 2.2 {
+  PRAGMA journal_mode = wal;
+} {1 {disk I/O error}}
+
+do_test 2.3 {
+  sqlite3 db2 test.db -readonly 1
+  breakpoint
+  db2 eval {
+    PRAGMA journal_mode = persist;
+    PRAGMA journal_mode = off;
+  }
+} {persist off}
+
+do_test 2.4 {
+  db2 eval {
+    SELECT * FROM t1
+  }
+} {abc def}
+
+finish_test
+
@@ -0,0 +1,70 @@
+# 2024 October 30
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+ifcapable !readonly_waljournal {
+  finish_test
+  return
+}
+
+set ::testprefix readonlyfault
+
+testvfs tvfs -default 1
+tvfs script at_vfs_callback
+tvfs filter {xDelete}
+
+set ::delete_shall_fail 0
+proc at_vfs_callback {method file z args} {
+  if {$::delete_shall_fail} {
+    return "SQLITE_IOERR"
+  }
+  return "SQLITE_OK"
+}
+
+reset_db
+do_execsql_test 1.0 {
+  BEGIN;
+    CREATE TABLE t1(a, b);
+    INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
+  COMMIT;
+}
+
+set ::delete_shall_fail 1
+do_catchsql_test 1.1 {
+  PRAGMA journal_mode = wal;
+} {1 {disk I/O error}}
+
+do_test 1.2 {
+  file exists test.db-journal
+} 1
+
+db_save_and_close
+
+# Injecting CANTOPEN errors doesn't work here. If such an error occurs
+# while trying to open a potentially hot journal to inspect its contents,
+# the error is ignored and the journal assumed to be hot. Leading to an
+# SQLITE_READONLY error. So only the other types of fault-injection are
+# tested here.
+#
+do_faultsim_test readonlyfault-1 -faults {oom* ioerr* inter* full*} -prep {
+  catch { db close }
+  db_restore
+  sqlite3 db test.db -readonly 1
+} -body {
+  execsql { SELECT count(*), sum(a), sum(b) FROM t1 }
+} -test {
+  faultsim_test_result {0 {3 9 12}} 
+}
+
+
+finish_test
@@ -0,0 +1,394 @@
+# 2017 August 9
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse1
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+forcedelete test.db2
+sqlite3 db2 test.db2
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
+  CREATE INDEX i1 ON t1(z);
+  PRAGMA schema_version;
+} {2}
+
+do_execsql_test -db db2 1.1 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
+  CREATE INDEX i1 ON t1(z);
+  PRAGMA schema_version;
+} {2}
+
+do_test 1.2 {
+  db close
+  db2 close
+  sqlite3 db2 test.db2 -shared-schema 1
+  sqlite3 db  test.db -shared-schema 1
+} {}
+
+do_execsql_test -db db2 1.3.1 {
+  INSERT INTO t1 VALUES(1, 2, 3);
+  INSERT INTO t1 VALUES(4, 5, 6);
+}
+
+do_execsql_test 1.3.2 {
+  SELECT * FROM t1;
+  PRAGMA integrity_check;
+} {ok}
+
+do_execsql_test -db db2 1.3.3 {
+  SELECT * FROM t1;
+  PRAGMA integrity_check;
+} {1 2 3 4 5 6 ok}
+
+sqlite3 db3 test.db2
+do_execsql_test -db db3 1.4.1 {
+  ALTER TABLE t1 ADD COLUMN a;
+}
+do_execsql_test -db db2 1.4.2 {
+  SELECT * FROM t1;
+} {1 2 3 {} 4 5 6 {}}
+do_execsql_test 1.4.3 {
+  SELECT * FROM t1;
+} {}
+
+db3 close
+sqlite3 db3 test.db
+do_execsql_test -db db3 1.5.0 {
+  CREATE TRIGGER tr1 AFTER INSERT ON t1 BEGIN
+    SELECT 1, 2, 3;
+  END;
+}
+
+# Check that the schema cannot be modified if the db was opened with
+# SQLITE_OPEN_REUSE_SCHEMA.
+#
+foreach {tn sql} {
+  1  { CREATE TABLE t2(x, y) }
+  2  { CREATE INDEX i2 ON t1(z) }
+  3  { CREATE VIEW v2 AS SELECT * FROM t2 }
+  4  { ALTER TABLE t1 RENAME TO t3 }
+  5  { ALTER TABLE t1 ADD COLUMN xyz }
+  6  { VACUUM }
+  7  { DROP INDEX i1 }
+  8  { DROP TABLE t1 }
+  9  { DROP TRIGGER tr1 }
+  10 { ANALYZE }
+  11 { ALTER TABLE t1 RENAME z TO zzz }
+} {
+  do_catchsql_test 1.5.$tn $sql {1 {attempt to modify read-only schema}}
+}
+
+#-------------------------------------------------------------------------
+#
+db2 close
+db3 close
+reset_db
+forcedelete test.db2
+ifcapable fts5 {
+  do_execsql_test 2.0 {
+    CREATE VIRTUAL TABLE ft USING fts5(a);
+    INSERT INTO ft VALUES('one'), ('two'), ('three');
+    ATTACH 'test.db2' AS aux;
+    CREATE VIRTUAL TABLE aux.ft USING fts5(a);
+    INSERT INTO aux.ft VALUES('aux1'), ('aux2'), ('aux3');
+  }
+
+  db close
+  sqlite3 db  test.db -shared-schema 1
+
+  do_execsql_test 2.1 {
+    ATTACH 'test.db2' AS aux;
+    SELECT * FROM main.ft;
+  } {one two three}
+
+breakpoint
+  do_execsql_test 2.2 {
+    SELECT * FROM aux.ft;
+  } {aux1 aux2 aux3}
+
+  do_execsql_test 2.2 {
+    SELECT * FROM aux.ft_content;
+  } {1 aux1 2 aux2 3 aux3}
+}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+forcedelete test.db2
+do_execsql_test 3.0 {
+  CREATE TABLE t1(a PRIMARY KEY, b, c);
+  CREATE VIEW v1 AS SELECT * FROM t1;
+  CREATE TRIGGER v1_ins INSTEAD OF INSERT ON v1 BEGIN
+    INSERT INTO t1 VALUES(new.a, new.b, new.c);
+  END;
+  CREATE TRIGGER v1_del INSTEAD OF DELETE ON v1 BEGIN
+    DELETE FROM t1 WHERE a=old.a;
+  END;
+  CREATE TRIGGER v1_up INSTEAD OF UPDATE ON v1 BEGIN
+    UPDATE t1 SET a=new.a, b=new.b, c=new.c WHERE a=old.a;
+  END;
+}
+forcecopy test.db test.db2
+
+do_test 3.1 {
+  sqlite3 db2 test.db2
+  execsql { INSERT INTO t1 VALUES(1, 2, 3) } db
+  execsql { INSERT INTO t1 VALUES(4, 5, 6) } db2
+  db2 close
+  execsql { ATTACH 'test.db2' AS aux; }
+} {}
+
+do_execsql_test 3.2 {
+  SELECT * FROM main.v1;
+} {1 2 3}
+
+do_execsql_test 3.3 {
+  SELECT * FROM aux.v1;
+} {4 5 6}
+
+db close
+sqlite3 db test.db -shared-schema 1
+
+do_execsql_test 3.4 { ATTACH 'test.db2' AS aux } {}
+do_execsql_test 3.5 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.6 { SELECT * FROM aux.v1  } {4 5 6}
+
+do_execsql_test 3.7.1 { INSERT INTO aux.t1 VALUES(8, 9, 10); }
+do_execsql_test 3.7.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.7.3 { SELECT * FROM aux.v1  } {4 5 6 8 9 10}
+
+do_execsql_test 3.8.1 { DELETE FROM aux.t1 WHERE b=5 }
+do_execsql_test 3.8.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.8.3 { SELECT * FROM aux.v1  } {8 9 10}
+
+do_execsql_test 3.9.1 { UPDATE aux.t1 SET b='abc' }
+do_execsql_test 3.9.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.9.3 { SELECT * FROM aux.v1  } {8 abc 10}
+
+do_execsql_test 3.10.1 { INSERT INTO aux.v1 VALUES(11, 12, 13) }
+do_execsql_test 3.10.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.10.3 { SELECT * FROM aux.v1  } {8 abc 10 11 12 13}
+
+do_execsql_test 3.11.1 { DELETE FROM aux.v1 WHERE b='abc' }
+do_execsql_test 3.11.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.11.3 { SELECT * FROM aux.v1  } {11 12 13}
+
+do_execsql_test 3.12.1 { UPDATE aux.v1 SET b='def' }
+do_execsql_test 3.12.2 { SELECT * FROM main.v1 } {1 2 3}
+do_execsql_test 3.12.3 { SELECT * FROM aux.v1  } {11 def 13}
+
+do_execsql_test 3.13.1 {
+  CREATE TEMP TRIGGER xyz AFTER INSERT ON aux.t1 BEGIN
+    INSERT INTO v1 VALUES(new.a, new.b, new.c);
+  END
+}
+do_execsql_test 3.13.2 {
+  INSERT INTO aux.v1 VALUES('x', 'y', 'z');
+}
+do_execsql_test 3.13.3 {
+  SELECT * FROM v1;
+} {1 2 3 x y z}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+forcedelete test.db2
+do_execsql_test 4.0 {
+  CREATE TABLE t1(a PRIMARY KEY, b, c UNIQUE);
+  CREATE TABLE del(a, b, c);
+  CREATE TRIGGER tr1 AFTER DELETE ON t1 BEGIN
+    INSERT INTO del VALUES(old.a, old.b, old.c);
+  END;
+}
+forcecopy test.db test.db2
+
+db close
+sqlite3 db test.db -shared-schema 1
+execsql { 
+  ATTACH 'test.db2' AS aux;
+  PRAGMA recursive_triggers = 1;
+}
+
+do_execsql_test 4.1 {
+  INSERT INTO main.t1 VALUES(1, 2, 3);
+  INSERT INTO aux.t1 VALUES(4, 5, 6);
+}
+
+do_execsql_test 4.2.1 {
+  INSERT OR REPLACE INTO aux.t1 VALUES('a', 'b', 6);
+  SELECT * FROM aux.t1;
+} {a b 6}
+do_execsql_test 4.2.2 { SELECT * FROM aux.del  } {4 5 6}
+do_execsql_test 4.2.3 { SELECT * FROM main.del } {}
+
+do_execsql_test 4.3.1 {
+  INSERT INTO aux.t1 VALUES('x', 'y', 'z');
+  UPDATE OR REPLACE aux.t1 SET c='z' WHERE a='a';
+} {}
+do_execsql_test 4.3.2 { SELECT * FROM aux.del  } {4 5 6 x y z}
+do_execsql_test 4.3.3 { SELECT * FROM main.del } {}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+do_execsql_test 5.0 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
+  CREATE TABLE t2(a INTEGER PRIMARY KEY, b, c);
+  CREATE INDEX i1 ON t1(b);
+  INSERT INTO t1 VALUES(1, 2, 3), (4, 5, 6);
+  ANALYZE;
+  PRAGMA writable_schema = 1;
+  DELETE FROM sqlite_stat1;
+}
+db close
+forcecopy test.db test.db2
+sqlite3 db test.db -shared-schema 1
+execsql { ATTACH 'test.db2' AS aux }
+
+foreach {tn sql} {
+  1 { CREATE TABLE t3(x) }
+  2 { DROP TABLE t2 }
+  3 { CREATE INDEX i2 ON t2(b) }
+  4 { DROP INDEX i1 }
+  5 { ALTER TABLE t1 ADD COLUMN d }
+  6 { ALTER TABLE t1 RENAME TO t3 }
+  7 { ALTER TABLE t1 RENAME c TO d }
+} {
+  do_catchsql_test 5.1.$tn $sql {1 {attempt to modify read-only schema}}
+}
+
+do_execsql_test 5.2.1 { ANALYZE aux.t1 } {}
+do_execsql_test 5.2.2 { SELECT * FROM aux.sqlite_stat1  } {t1 i1 {2 1}}
+do_execsql_test 5.2.3 { SELECT * FROM main.sqlite_stat1 } {}
+
+do_test 5.3.0 {
+  sqlite3 db2 test.db2
+  db2 eval { 
+    PRAGMA writable_schema = 1;
+    DELETE FROM sqlite_stat1;
+  }
+} {}
+
+do_execsql_test 5.3.1 { SELECT * FROM aux.sqlite_stat1  } {}
+do_execsql_test 5.3.2 { ANALYZE aux } {}
+do_execsql_test 5.3.3 { SELECT * FROM aux.sqlite_stat1  } {t1 i1 {2 1}}
+do_execsql_test 5.3.4 { SELECT * FROM main.sqlite_stat1 } {}
+
+#-------------------------------------------------------------------------
+# Attempting to run ANALYZE when the required sqlite_statXX functions
+# are missing is an error (because it would modify the database schema).
+#
+reset_db
+do_execsql_test 5.4 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
+  CREATE TABLE t2(a INTEGER PRIMARY KEY, b, c);
+  CREATE INDEX i1 ON t1(b);
+  INSERT INTO t1 VALUES(1, 2, 3), (4, 5, 6);
+}
+db close
+sqlite3 db test.db -shared-schema 1
+foreach {tn sql} {
+  1 { ANALYZE }
+  2 { ANALYZE t1 }
+  3 { ANALYZE i1 }
+  4 { ANALYZE main }
+  5 { ANALYZE main.t1 }
+  6 { ANALYZE main.i1 }
+} {
+  do_catchsql_test 5.4.$tn $sql {1 {attempt to modify read-only schema}}
+}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+do_execsql_test 6.0 {
+  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
+  CREATE VIEW v1 AS SELECT * FROM t1;
+}
+db close
+forcecopy test.db test.db2
+sqlite3 db test.db -shared-schema 1
+execsql { ATTACH 'test.db2' AS aux }
+
+do_execsql_test 6.1 {
+  INSERT INTO main.t1(a) VALUES(1), (2), (3);
+  INSERT INTO aux.t1(a) VALUES(4), (5), (6);
+  CREATE TEMP TABLE t2(i,t);
+  INSERT INTO t2 VALUES(2, 'two'), (5, 'five');
+}
+
+do_execsql_test 6.2 {
+  SELECT t FROM t2 WHERE i IN (SELECT a FROM aux.t1)
+} {five}
+do_execsql_test 6.3 {
+  SELECT t FROM t2 WHERE i IN (SELECT a FROM aux.v1)
+} {five}
+
+#-------------------------------------------------------------------------
+#
+reset_db
+do_execsql_test 7.0 {
+  CREATE TABLE p1(a PRIMARY KEY, b);
+  CREATE TABLE p2(a PRIMARY KEY, b);
+  CREATE TABLE c1(x REFERENCES p1 ON UPDATE CASCADE ON DELETE CASCADE);
+}
+
+db close
+forcecopy test.db test.db2
+sqlite3 db test.db -shared-schema 1
+execsql { ATTACH 'test.db2' AS aux }
+
+do_execsql_test 7.1 {
+  INSERT INTO aux.p1 VALUES(1, 'one');
+  INSERT INTO aux.p1 VALUES(2, 'two');
+  PRAGMA foreign_keys = on;
+}
+
+do_execsql_test 7.2 {
+  INSERT INTO aux.c1 VALUES(2);
+}
+
+do_execsql_test 7.3.1 {
+  PRAGMA foreign_keys = off;
+  INSERT INTO main.p2 SELECT * FROM aux.p1;
+}
+do_execsql_test 7.3.2 {
+  SELECT * FROM main.p2;
+} {1 one 2 two}
+
+do_execsql_test 7.3.3 {
+  INSERT INTO aux.p2 VALUES(1, 2);
+}
+
+do_execsql_test 7.3.4 {
+  SELECT main.p2.a FROM main.p2, aux.p2;
+} {1 2}
+
+do_execsql_test 7.3.5 {
+  SELECT * FROM main.p2, aux.p2;
+} {1 one 1 2   2 two 1 2}
+
+do_execsql_test 7.4 {
+  SELECT count(*) FROM aux.p2;
+} {1}
+
+
+finish_test
@@ -0,0 +1,336 @@
+# 2017 August 9
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse2
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
+  CREATE INDEX i1 ON t1(z);
+  PRAGMA schema_version;
+} {2}
+
+do_test 1.2 {
+  catch { db close }
+  catch { db2 close }
+  sqlite3 db2 test.db -shared-schema 1
+  sqlite3 db  test.db -shared-schema 1
+} {}
+
+do_execsql_test -db db2 1.3.1 {
+  INSERT INTO t1 VALUES(1, 2, 3);
+}
+
+do_execsql_test -db db2 1.3.2 {
+  INSERT INTO t1 VALUES(4, 5, 6);
+}
+
+do_execsql_test 1.3.3 {
+  SELECT * FROM t1;
+} {1 2 3 4 5 6}
+
+#--------------------------------------------------------------------------
+db2 close
+reset_db
+ifcapable fts5 {
+  do_execsql_test 2.0 {
+    CREATE VIRTUAL TABLE ft USING fts5(c);
+    INSERT INTO ft VALUES('one two three');
+  }
+  db close
+  sqlite3 db test.db -shared-schema 1
+
+  do_execsql_test 2.1 {
+    SELECT * FROM ft
+  } {{one two three}}
+}
+
+#--------------------------------------------------------------------------
+reset_db
+do_execsql_test 3.0 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
+  CREATE INDEX i1 ON t1(z);
+  PRAGMA schema_version;
+} {2}
+
+do_test 3.1 {
+  sqlite3 db1 test.db -shared-schema 1
+  sqlite3 db2 test.db -shared-schema 1
+} {}
+
+do_execsql_test -db db1 3.2.1 { SELECT * FROM t1 }
+do_execsql_test -db db2 3.2.2 { SELECT * FROM t1 }
+
+register_schemapool_module db
+do_execsql_test 3.3 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=2 nschema=1 ndelete=0}
+
+sqlite3 db3 test.db -shared-schema 1
+register_schemapool_module db3
+
+do_execsql_test 3.5 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=2 nschema=1 ndelete=0}
+
+do_execsql_test -db db3 3.6 { 
+  SELECT * FROM t1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=3 nschema=1 ndelete=0}
+
+do_execsql_test 3.7 { 
+  CREATE TABLE t2(x);
+}
+
+do_execsql_test 3.8 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=3 nschema=1 ndelete=0}
+
+do_execsql_test -db db1 3.9.1 { SELECT * FROM t1 }
+do_execsql_test 3.9.2 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=1 nschema=1 ndelete=0 nref=2 nschema=1 ndelete=0}
+
+do_execsql_test -db db2 3.10.1 { SELECT * FROM t1 }
+do_execsql_test 3.10.2 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool ORDER BY 1;
+} {nref=1 nschema=1 ndelete=0 nref=2 nschema=1 ndelete=0}
+
+do_execsql_test -db db3 3.11.1 { SELECT * FROM t1 }
+do_execsql_test 3.11.2 { 
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=3 nschema=1 ndelete=0}
+
+#--------------------------------------------------------------------------
+catch {db1 close}
+catch {db2 close}
+catch {db3 close}
+reset_db
+do_execsql_test 4.0.1 {
+  CREATE TABLE x1(a, b, c);
+  CREATE INDEX x1a ON x1(a);
+  CREATE INDEX x1b ON x1(b);
+}
+do_test 4.0.2 {
+  db close
+  for {set i 1} {$i < 6} {incr i} {
+    forcedelete test.db${i}-journal test.db${i}-wal test.db${i}-wal2 
+    forcecopy test.db test.db${i}
+  }
+  sqlite3 db  test.db
+  sqlite3 db2 test.db -shared-schema 1
+} {}
+
+register_schemapool_module db
+do_execsql_test 4.0.3 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {}
+
+do_test 4.1.1 {
+  execsql { 
+    ATTACH 'test.db1' AS db1; 
+    ATTACH 'test.db2' AS db2;
+    ATTACH 'test.db3' AS db3;
+    ATTACH 'test.db4' AS db4;
+    ATTACH 'test.db5' AS db5;
+  } db2
+} {}
+do_execsql_test 4.1.2 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=1 nschema=1 ndelete=0}
+do_execsql_test -db db2 4.1.3 {
+  SELECT * FROM db3.x1
+}
+do_execsql_test 4.1.4 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=2 nschema=1 ndelete=0}
+do_execsql_test -db db2 4.1.5 {
+  SELECT * FROM db2.x1
+}
+do_execsql_test 4.1.6 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=3 nschema=1 ndelete=0}
+do_execsql_test -db db2 4.1.7 {
+  SELECT * FROM x1
+}
+do_execsql_test 4.1.8 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=3 nschema=1 ndelete=0}
+
+do_test 4.2.1 {
+  catchsql { SELECT * FROM abc } db2
+} {1 {no such table: abc}}
+do_execsql_test 4.2.2 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=6 nschema=1 ndelete=0}
+
+register_schemapool_module db2
+do_execsql_test -db db2 4.3.1 {
+  INSERT INTO x1 VALUES(1, 2, 3);
+  INSERT INTO db1.x1 VALUES(4, 5, 6);
+  INSERT INTO db2.x1 VALUES(7, 8, 9);
+  INSERT INTO db3.x1 VALUES(10, 11, 12);
+  INSERT INTO db4.x1 VALUES(13, 14, 15);
+  INSERT INTO db5.x1 VALUES(16, 17, 18);
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=6 nschema=1 ndelete=0}
+
+do_execsql_test -db db2 4.3.2 {
+  SELECT * FROM db5.x1;
+  SELECT * FROM db4.x1;
+  SELECT * FROM db3.x1;
+  SELECT * FROM db2.x1;
+  SELECT * FROM db1.x1;
+  SELECT * FROM x1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {
+  16 17 18  13 14 15  10 11 12  7 8 9  4 5 6  1 2 3
+  nref=6 nschema=1 ndelete=0
+}
+
+do_execsql_test -db db2 4.3.3 {
+  UPDATE x1 SET a=a+10;
+  UPDATE db5.x1 SET a=a+10;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {
+  nref=6 nschema=1 ndelete=0
+}
+
+do_execsql_test -db db2 4.3.4 {
+  SELECT * FROM db5.x1;
+  SELECT * FROM db4.x1;
+  SELECT * FROM db3.x1;
+  SELECT * FROM db2.x1;
+  SELECT * FROM db1.x1;
+  SELECT * FROM x1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {
+  26 17 18  13 14 15  10 11 12  7 8 9  4 5 6  11 2 3
+  nref=6 nschema=1 ndelete=0
+}
+
+do_execsql_test -db db2 4.3.5 {
+  DELETE FROM db3.x1;
+  DELETE FROM x1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {
+  nref=6 nschema=1 ndelete=0
+}
+
+do_execsql_test -db db2 4.3.6 {
+  SELECT * FROM db5.x1;
+  SELECT * FROM db4.x1;
+  SELECT * FROM db3.x1;
+  SELECT * FROM db2.x1;
+  SELECT * FROM db1.x1;
+  SELECT * FROM x1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {
+  26 17 18  13 14 15  7 8 9  4 5 6 
+  nref=6 nschema=1 ndelete=0
+}
+
+do_execsql_test -db db2 4.3.6 {
+  SELECT * FROM db5.x1, db4.x1, db1.x1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {26 17 18 13 14 15 4 5 6 nref=6 nschema=3 ndelete=0}
+
+#--------------------------------------------------------------------------
+# Test the incremental-blob API with REUSE_SCHEMA connections.
+#
+catch {db1 close}
+catch {db2 close}
+catch {db3 close}
+reset_db
+do_execsql_test 5.0.1 {
+  CREATE TABLE bbb(a INTEGER PRIMARY KEY, b);
+}
+db close
+do_test 5.0.2 {
+  sqlite3 db2 test.db -shared-schema 1
+  register_schemapool_module db2
+  for {set i 1} {$i<6} {incr i} {
+    forcedelete test.db${i}-journal test.db${i}-wal test.db${i}-wal2 
+    forcecopy test.db test.db${i}
+    sqlite3 db test.db${i}
+    db eval { INSERT INTO bbb VALUES(123, 'database_' || $i) }
+    db close
+    db2 eval "ATTACH 'test.db${i}' AS db${i}"
+  }
+  execsql {
+    SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+      FROM schemapool;
+  } db2
+} {nref=6 nschema=1 ndelete=0}
+
+do_test 5.1.1 {
+  set res [list]
+  for {set i 1} {$i<6} {incr i} {
+    set chan [db2 incrblob db${i} bbb b 123]
+    lappend res [gets $chan]
+    close $chan
+  }
+  set res
+} {database_1 database_2 database_3 database_4 database_5}
+
+do_execsql_test -db db2 5.1.2 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=6 nschema=1 ndelete=0}
+
+do_test 5.2.1 {
+  sqlite3_table_column_metadata db2 main bbb a
+} {INTEGER BINARY 0 1 0}
+do_test 5.2.2 {
+  sqlite3_table_column_metadata db2 main bbb b
+} {{} BINARY 0 0 0}
+
+do_execsql_test -db db2 5.2.3 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {nref=6 nschema=1 ndelete=0}
+
+do_execsql_test -db db2 5.2.4 {
+  PRAGMA integrity_check;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete
+  FROM schemapool;
+} {ok nref=6 nschema=1 ndelete=5}
+
+finish_test
@@ -0,0 +1,356 @@
+# 2019 February 12
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse3
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE, z);
+  CREATE INDEX i1 ON t1(z);
+  CREATE TABLE t2(a);
+} {}
+
+db close
+sqlite3 db test.db -shared-schema 1
+
+do_execsql_test 1.1 {
+  CREATE TEMP VIEW v1 AS SELECT * FROM t1;
+  SELECT * FROM v1;
+}
+
+do_execsql_test 1.2 {
+  CREATE TEMP TRIGGER tr1 AFTER INSERT ON t1 BEGIN
+    INSERT INTO t2 VALUES(new.x);
+  END;
+}
+
+do_execsql_test 1.3 {
+  INSERT INTO t1 VALUES(1, 2, 3);
+}
+
+do_execsql_test 1.4 {
+  SELECT * FROM t2
+} {1}
+
+do_execsql_test 1.5 {
+  SELECT * FROM v1
+} {1 2 3}
+
+do_execsql_test 1.6 {
+  BEGIN;
+    DROP TRIGGER tr1;
+  ROLLBACK;
+}
+
+do_execsql_test 1.7 {
+  SELECT * FROM v1
+} {1 2 3}
+
+do_execsql_test 1.8 {
+  INSERT INTO t1 VALUES(4, 5, 6);
+  SELECT * FROM t2
+} {1 4}
+
+do_execsql_test 1.9 {
+  SELECT * FROM v1
+} {1 2 3 4 5 6}
+
+#-------------------------------------------------------------------------
+# Test error messages when parsing the schema with a REUSE_SCHEMA 
+# connection.
+reset_db
+do_execsql_test 2.0 {
+  CREATE TABLE x1(a, b, c);
+  CREATE TABLE y1(d, e, f);
+  PRAGMA writable_schema = 1;
+  UPDATE sqlite_master SET sql = 'CREATE TBL y1(d, e, f)' WHERE name = 'y1';
+}
+db close
+
+sqlite3 db test.db -shared-schema 1
+do_catchsql_test 2.1 {
+  SELECT * FROM x1;
+} {1 {malformed database schema (y1) - near "TBL": syntax error}}
+
+do_catchsql_test 2.2 {
+  SELECT * FROM x1;
+} {1 {malformed database schema (y1) - near "TBL": syntax error}}
+
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 3.0 {
+  CREATE TABLE x1(a, b, c);
+  CREATE INDEX i1 ON x1(a, b, c);
+  CREATE TRIGGER tr1 AFTER INSERT ON x1 BEGIN
+    SELECT 1, 2, 3, 4, 5;
+  END;
+  INSERT INTO x1 VALUES(1, 2, 3);
+}
+sqlite3 db1 test.db -shared-schema 1
+
+do_test 3.1 {
+  execsql { SELECT * FROM x1 } db1
+  set N [lindex [sqlite3_db_status db1 SCHEMA_USED 0] 1]
+  expr $N==$N
+} 1
+
+sqlite3 db2 test.db -shared-schema 1
+do_test 3.2 {
+  execsql { SELECT * FROM x1 } db2
+  set N2 [lindex [sqlite3_db_status db2 SCHEMA_USED 0] 1]
+  expr $N2>($N/2) && $N2<($N/2)+400
+} 1
+
+sqlite3 db3 test.db -shared-schema 1
+sqlite3 db4 test.db -shared-schema 1
+do_test 3.3 {
+  execsql { SELECT * FROM x1 } db3
+  execsql { SELECT * FROM x1 } db4
+  set N4 [lindex [sqlite3_db_status db2 SCHEMA_USED 0] 1]
+  set M [expr 2*($N-$N2)]
+  set {} {}
+} {}
+do_test 3.3.1 { expr {(($M / 4) + $N-$M)} } "#/$N4/"
+
+catch { db1 close }
+catch { db2 close }
+catch { db3 close }
+catch { db4 close }
+
+#-------------------------------------------------------------------------
+# 4.1 Test the REINDEX command.
+# 4.2 Test CREATE TEMP ... commands.
+#
+reset_db
+do_execsql_test 4.1.0 {
+  CREATE TABLE x1(a, b, c);
+  CREATE INDEX x1a ON x1(a);
+  CREATE INDEX x1b ON x1(b);
+  CREATE INDEX x1c ON x1(c);
+}
+db close
+sqlite3 db test.db -shared-schema 1
+
+do_execsql_test 4.1.1 {
+  REINDEX x1;
+  REINDEX x1a;
+  REINDEX x1b;
+  REINDEX x1c;
+  REINDEX;
+}
+
+do_test 4.1.2 {
+  for {set i 1} {$i < 5} {incr i} {
+    forcedelete test.db${i} test.db${i}-wal test.db${i}-journal
+    forcecopy test.db test.db${i}
+    execsql "ATTACH 'test.db${i}' AS db${i}"
+  }
+  register_schemapool_module db
+  set {} {}
+  execsql { 
+    SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool 
+  }
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.1.3 {
+  REINDEX  x1;
+  REINDEX  x1a;
+  REINDEX  x1b;
+  REINDEX  x1c;
+  REINDEX  db1.x1a;
+  REINDEX  db2.x1b;
+  REINDEX  db3.x1c;
+}
+
+do_execsql_test 4.1.4 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool 
+} {nref=5 nschema=1 ndelete=28}
+
+#-------------------------------------------------------------------------
+db close
+sqlite3 db test.db -shared-schema 1
+register_schemapool_module db
+do_execsql_test 4.2.0 {
+  ATTACH 'test.db1' AS db1;
+  ATTACH 'test.db2' AS db2;
+  ATTACH 'test.db3' AS db3;
+  ATTACH 'test.db4' AS db4;
+
+  SELECT * FROM db1.x1;
+  SELECT * FROM db2.x1;
+  SELECT * FROM db3.x1;
+  SELECT * FROM db4.x1;
+}
+
+do_execsql_test 4.2.1 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.2 {
+  CREATE TEMP TABLE t1(a, b, c);
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.3 {
+  CREATE INDEX t1a ON t1(a);
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.4 {
+  CREATE TRIGGER tr1 AFTER INSERT ON t1 BEGIN
+    SELECT 1,2,3,4;
+  END;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.5 {
+  DROP TABLE t1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.6 {
+  CREATE TEMP TRIGGER tr1 AFTER INSERT ON db2.x1 BEGIN
+    SELECT 1,2,3,4;
+  END;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=0}
+
+do_execsql_test 4.2.7 {
+  DROP TRIGGER tr1;
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema, 'ndelete=' || nDelete 
+    FROM schemapool; 
+} {nref=5 nschema=1 ndelete=4}
+
+#--------------------------------------------------------------------------
+reset_db
+do_execsql_test 5.0 {
+  CREATE TABLE t1(a, b);
+  CREATE TABLE t2(a, b);
+  CREATE TABLE t3(a, b);
+}
+
+sqlite3 db2 test.db -shared-schema 1
+register_schemapool_module db2
+
+do_execsql_test 5.1 {
+  PRAGMA writable_schema = 1;
+  UPDATE sqlite_master SET sql='CREATE TABLE t3 a,b' WHERE name = 't3';
+}
+
+do_test 5.2 { 
+  catchsql { SELECT * FROM t1 } db2
+} {1 {malformed database schema (t3) - near "a": syntax error}}
+
+do_test 5.3 { 
+  catchsql { SELECT nref,nschema FROM schemapool } db2
+} {1 {malformed database schema (t3) - near "a": syntax error}}
+
+do_execsql_test 5.4 {
+  PRAGMA writable_schema = 1;
+  UPDATE sqlite_master SET sql='CREATE TABLE t3(a,b)' WHERE name = 't3';
+}
+
+do_test 5.5 { 
+  catchsql { SELECT nref,nschema FROM schemapool } db2
+} {0 {1 1}}
+
+db2 close
+db close
+do_test 5.6.1 {
+  forcedelete test.db2 test.db2-wal test.db2-journal
+  forcecopy test.db test.db2
+  sqlite3 db test.db
+  sqlite3 db2 test.db  -shared-schema 1
+  sqlite3 db3 test.db2 -shared-schema 1
+  register_schemapool_module db
+} {}
+
+do_execsql_test -db db2 5.6.2 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.3 { SELECT * FROM t1 }
+do_execsql_test 5.6.4 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+  CREATE TABLE t4(x);
+  DROP TABLE t4;
+} {nref=2 nschema=1}
+do_execsql_test -db db2 5.6.5 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.6 { SELECT * FROM t1 }
+do_execsql_test 5.6.7 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+  ATTACH 'test.db2' AS db2;
+  CREATE TABLE db2.t4(x);
+  DROP TABLE db2.t4;
+} {nref=1 nschema=1 nref=1 nschema=1}
+do_execsql_test -db db2 5.6.8 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.9 { SELECT * FROM t1 }
+do_execsql_test 5.6.10 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+} {nref=2 nschema=1}
+
+#-------------------------------------------------------------------------
+db2 close
+db3 close
+reset_db
+do_execsql_test 6.0 {
+  CREATE TABLE t1(a, b);
+  CREATE TABLE t2(a, b);
+  CREATE TABLE t3(a, b);
+}
+
+do_test 6.1 {
+  db close
+  sqlite3 db test.db -shared-schema 1
+  for {set i 1} {$i < 5} {incr i} {
+    set base "test.db$i"
+    set nm "aux$i"
+    forcedelete $base $base-wal $base-journal
+    forcecopy test.db $base
+    execsql "ATTACH '$base' AS $nm"
+  }
+} {}
+
+do_test 6.2 {
+  set N1 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  set N2 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  expr {$N1>0 && $N2>0 && $N1==$N2}
+} {1}
+
+do_test 6.3 {
+  execsql { SELECT * FROM main.t1 }
+  set N1 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  set N2 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  expr {$N1>0 && $N2>0 && $N1==$N2}
+} {1}
+
+do_test 6.4 {
+  execsql { SELECT * FROM aux1.t1 }
+  set N3 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  set N4 [lindex [sqlite3_db_status db SCHEMA_USED 0] 1]
+  list $N3 $N4
+} "#/$N1 $N1/"
+
+finish_test
@@ -0,0 +1,174 @@
+# 2019 February 12
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse4
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+foreach {tn sharedschema} {
+  1 0  
+  2 1  
+} {
+  catch {db2 close}
+  reset_db
+
+  do_execsql_test 1.$tn.0 {
+    CREATE TABLE x1(a, b);
+    CREATE INDEX x1a ON x1(a);
+    CREATE INDEX x1b ON x1(b);
+    CREATE TABLE x2(a, b);
+  }
+  db close
+  
+  do_test 1.$tn.1 {
+    for {set i 1} {$i<4} {incr i} {
+      forcedelete test.db$i test.db$i-journal test.db$i-wal
+      forcecopy test.db test.db$i
+    }
+  
+    sqlite3 db test.db -shared-schema $sharedschema
+    for {set i 1} {$i<4} {incr i} {
+      execsql " ATTACH 'test.db$i' AS db$i "
+    }
+  } {}
+  
+  do_execsql_test 1.$tn.2 {
+    WITH s(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM s WHERE i<10 )
+    INSERT INTO x1 SELECT i, i FROM s;
+  
+    INSERT INTO db3.x2 SELECT * FROM x1;
+    INSERT INTO db2.x1 SELECT * FROM db3.x2;
+    CREATE TEMP TRIGGER tr1 AFTER INSERT ON db2.x2 BEGIN
+      INSERT INTO x1 VALUES(new.a, new.b);
+    END;
+    INSERT INTO db2.x2 SELECT * FROM x1 WHERE a%2;
+    DELETE FROM x1 WHERE a<3;
+    INSERT INTO db3.x1 SELECT * FROM db2.x2;
+  
+    DETACH db3;
+    ATTACH 'test.db3' AS db3;
+  
+    UPDATE db3.x1 SET a=a-10 WHERE b NOT IN (SELECT b FROM db2.x2);
+  
+    CREATE TEMP TABLE x1(a, b);
+    INSERT INTO db2.x2 VALUES(50, 60), (60, 70), (80, 90);
+    ALTER TABLE x1 RENAME TO x2;
+    ALTER TABLE x2 ADD COLUMN c;
+    ALTER TABLE x2 RENAME a TO aaa;
+    DELETE FROM x1 WHERE b>8;
+    UPDATE db3.x2 SET b=b*10;
+  
+    BEGIN;
+      CREATE TEMP TABLE x5(x);
+      INSERT INTO x5 VALUES(1);
+    ROLLBACK;
+  
+    INSERT INTO main.x2 VALUES(123, 456);
+  }
+  
+  integrity_check 1.$tn.3
+  
+  do_execsql_test 1.$tn.4 {
+    SELECT * FROM main.x1; SELECT 'xxx';
+    SELECT * FROM main.x2; SELECT 'xxx';
+    SELECT * FROM temp.x2; SELECT 'xxx';
+  
+    SELECT * FROM db1.x1; SELECT 'xxx';
+    SELECT * FROM db1.x2; SELECT 'xxx';
+    SELECT * FROM db2.x1; SELECT 'xxx';
+    SELECT * FROM db2.x2; SELECT 'xxx';
+    SELECT * FROM db3.x1; SELECT 'xxx';
+    SELECT * FROM db3.x2; SELECT 'xxx';
+  } {
+    3 3 4 4 5 5 6 6 7 7 8 8 3 3 5 5 7 7 xxx 
+    123 456 xxx 
+    50 60 {} 60 70 {} 80 90 {} xxx
+    xxx
+    xxx
+    1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 xxx
+    1 1 3 3 5 5 7 7 9 9 50 60 60 70 80 90 xxx
+    1 1 3 3  5 5 7 7 9 9 xxx 
+    1 10 2 20 3 30 4 40 5 50 6 60 7 70 8 80 9 90 10 100 xxx
+  }
+  
+  do_test 1.$tn.5.1 {
+    sqlite3 db2 test.db
+    db2 eval { CREATE TABLE x3(x) }
+  } {}
+  do_execsql_test 1.$tn.5.2 {
+    SELECT * FROM main.x1; SELECT 'xxx';
+    SELECT * FROM main.x2; SELECT 'xxx';
+    SELECT * FROM main.x3; SELECT 'xxx';
+  } {
+    3 3 4 4 5 5 6 6 7 7 8 8 3 3 5 5 7 7 xxx 
+    123 456 xxx 
+    xxx
+  }
+}
+
+#-------------------------------------------------------------------------
+# Test some PRAGMA statements with shared-schema connections.
+#
+db2 close
+reset_db
+do_execsql_test 2.0 {
+  CREATE TABLE t1(a, b, c);
+  CREATE INDEX t1abc ON t1(a, b, c);
+}
+
+foreach {tn pragma nSchema nDelete} {
+  1 "PRAGMA synchronous = OFF"     1 0
+  2 "PRAGMA cache_size = 200"      1 0
+  3 "PRAGMA aux2.integrity_check"  1 0
+  4 "PRAGMA      integrity_check"  1 5
+  5 "PRAGMA index_info=t1abc"      1 5
+  6 "PRAGMA aux3.index_info=t1abc" 1 0
+  7 "PRAGMA journal_mode"          1 0
+  8 "PRAGMA aux2.wal_checkpoint"   1 0
+  9 "PRAGMA wal_checkpoint"        1 0
+} {
+  do_test 2.$tn.1 {
+    catch { db close }
+    catch { db2 close }
+    for {set i 1} {$i < 6} {incr i} {
+      forcedelete "test.db$i" "test.db${i}-wal" "test.db${i}-journal"
+      forcecopy test.db test.db$i
+    }
+    sqlite3 db2 test.db -shared-schema 1
+    for {set i 1} {$i < 6} {incr i} {
+      execsql "ATTACH 'test.db$i' AS aux$i" db2
+    }
+  } {}
+
+  sqlite3 db test.db
+  register_schemapool_module db
+
+  do_test 2.$tn.2 {
+    execsql $pragma db2
+    execsql { SELECT 'nschema='||nschema, 'ndelete='||nDelete FROM schemapool }
+  } "nschema=$nSchema ndelete=$nDelete"
+
+  do_test 2.$tn.3 {
+    execsql {
+      SELECT * FROM main.t1,aux1.t1,aux2.t1,aux3.t1,aux4.t1,aux5.t1
+    } db2
+    execsql { SELECT 'nschema=' || nschema, 'nref=' || nref FROM schemapool }
+  } "nschema=6 nref=6"
+}
+
+finish_test
@@ -0,0 +1,125 @@
+# 2019 February 26
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse5
+set CLI [test_find_cli]
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x, y);
+  CREATE TABLE t2(a, b, c);
+  CREATE INDEX t1x ON t1(x);
+  CREATE INDEX t1y ON t1(y);
+  CREATE VIEW v1 AS SELECT * FROM t2;
+}
+
+foreach {tn sql out1 out2} {
+  1 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1x ON t1(x);
+    CREATE INDEX t1y ON t1(y);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+  } {
+    test.db2 is compatible
+  } {}
+
+  2 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1x ON t1(x);
+    CREATE INDEX t1y ON t1(y);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+    CREATE TABLE x1(x);
+    DROP TABLE x1;
+  } {
+    test.db2 is NOT compatible (schema cookie)
+  } {
+    Fixing test.db2... test.db2 is compatible
+  }
+
+  3 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1y ON t1(y);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+  } {
+    test.db2 is NOT compatible (objects)
+  } {}
+
+  4 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1x ON t1(X);
+    CREATE INDEX t1y ON t1(y);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+  } {
+    test.db2 is NOT compatible (SQL)
+  } {}
+
+  5 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1y ON t1(y);
+    CREATE INDEX t1x ON t1(x);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+  } {
+    test.db2 is NOT compatible (root pages)
+  } {
+    Fixing test.db2... test.db2 is compatible
+  }
+
+  6 {
+    CREATE TABLE t1(x, y);
+    CREATE TABLE t2(a, b, c);
+    CREATE INDEX t1x ON t1(x);
+    CREATE INDEX t1y ON t1(y);
+    CREATE VIEW v1 AS SELECT * FROM t2;
+    DROP INDEX t1x;
+    CREATE INDEX t1x ON t1(x);
+  } {
+    test.db2 is NOT compatible (order of sqlite_master rows)
+  } {
+    Fixing test.db2... test.db2 is compatible
+  }
+
+} {
+  forcedelete test.db2
+  sqlite3 db2 test.db2
+  db2 eval $sql
+  db2 close
+
+  if {$out2==""} {set out2 $out1}
+
+  do_test 1.$tn.1 {
+    catchcmd test.db ".shared-schema check test.db2"
+  } [list 0 [string trim $out1]]
+
+  do_test 1.$tn.2 {
+    catchcmd test.db ".shared-schema fix test.db2"
+  } [list 0 [string trim $out2]]
+
+  do_test 1.$tn.3 {
+    catchcmd test.db2 "PRAGMA integrity_check"
+  } [list 0 ok]
+}
+
+
+finish_test
+
@@ -0,0 +1,143 @@
+# 2019 February 26
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reuse6
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x, y);
+  CREATE TABLE t2(a, b, c);
+  CREATE INDEX t1x ON t1(x);
+  CREATE INDEX t1y ON t1(y);
+  CREATE VIEW v1 AS SELECT * FROM t2;
+
+  INSERT INTO t1 VALUES(1, 2), (3, 4), (5, 6);
+  INSERT INTO t2 VALUES('a', 'b', 'c'), ('d', 'e', 'f'), ('g', 'h', 'i');
+
+  ATTACH 'test.db2' AS aux;
+  CREATE TABLE t3(i, ii);
+  INSERT INTO t3 VALUES(10, 20);
+}
+
+sqlite3 db1 test.db -shared-schema 1
+sqlite3 db2 test.db -shared-schema 1
+
+do_execsql_test -db db1 1.1 {
+  ATTACH 'test.db2' AS aux;
+}
+
+do_test 1.2 {
+  execsql {SELECT * FROM t3} db1
+} {10 20}
+
+do_execsql_test -db db2 1.3 {
+  ATTACH 'test.db2' AS aux;
+}
+
+do_test 1.3 {
+  execsql {SELECT * FROM t3} db1
+} {10 20}
+
+do_execsql_test -db db2 1.5 {
+  SELECT * FROM t3;
+} {10 20}
+
+do_test 1.6 {
+  execsql {SELECT * FROM t3} db1
+} {10 20}
+
+db1 close
+db2 close
+
+#-------------------------------------------------------------------------
+reset_db
+forcedelete test.db2
+forcedelete test.db3
+do_execsql_test 2.0 {
+  CREATE TABLE t1(x, y);
+  ATTACH 'test.db2' AS aux2;
+  CREATE TABLE aux2.t2(x, y);
+  ATTACH 'test.db3' AS aux3;
+  CREATE TABLE aux3.t3(x, y);
+}
+
+sqlite3 db1 test.db -shared-schema 1
+do_execsql_test -db db1 2.1 {
+  ATTACH 'test.db2' AS aux2;
+  ATTACH 'test.db3' AS aux3;
+}
+
+do_test 2.2.1 {
+  catchsql { SELECT * FROM aux2.nosuchtable } db1
+} {1 {no such table: aux2.nosuchtable}}
+do_test 2.2.2 {
+  sqlite3_errcode db1
+} {SQLITE_ERROR}
+db1 close
+
+#-------------------------------------------------------------------------
+reset_db
+forcedelete test.db2
+ifcapable fts5 {
+  do_execsql_test 3.0 {
+    CREATE VIRTUAL TABLE ft USING fts5(a, b);
+    ATTACH 'test.db2' AS aux;
+    CREATE TABLE aux.t1(x, y, z);
+  }
+
+  sqlite3 db1 test.db -shared-schema 1
+  do_execsql_test -db db1 3.1 {
+    ATTACH 'test.db2' AS aux;
+  }
+
+  do_execsql_test -db db1 3.2 {
+    SELECT * FROM main.ft, aux.t1;
+  }
+  db1 close
+}
+
+#-------------------------------------------------------------------------
+reset_db
+forcedelete test.db2
+ifcapable fts5 {
+  do_execsql_test 4.0 {
+    CREATE VIRTUAL TABLE ft USING fts5(a, b);
+  }
+  forcecopy test.db test.db2
+
+  sqlite3 db1 test.db -shared-schema 1
+  do_execsql_test -db db1 4.1 {
+    ATTACH 'test.db2' AS aux;
+    SELECT * FROM main.ft;
+    SELECT * FROM aux.ft;
+  }
+
+  do_execsql_test -db db1 4.2 {
+    SELECT * FROM main.ft, aux.ft
+  }
+}
+
+
+
+
+
+
+
+finish_test
+
@@ -0,0 +1,56 @@
+# 2019 February 12
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reusefault
+
+ifcapable !sharedschema {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  PRAGMA cache_size = 10;
+  CREATE TABLE t1(a UNIQUE, b UNIQUE);
+  INSERT INTO t1 VALUES(1, 2), (3, 4);
+}
+faultsim_save_and_close
+
+do_faultsim_test 1.1 -prep {
+  catch {db close}
+  faultsim_restore
+  sqlite3 db test.db -shared-schema 1
+} -body {
+  execsql { SELECT * FROM t1 }
+} -test {
+  faultsim_test_result {0 {1 2 3 4}}
+}
+
+do_faultsim_test 1.2 -prep {
+  catch {db close}
+  catch {db2 close}
+  faultsim_restore
+  sqlite3 db test.db -shared-schema 1
+  execsql { SELECT * FROM t1 }
+  sqlite3 db2 test.db
+  db2 eval {CREATE TABLE a(a)}
+  db2 close
+} -body {
+  execsql { SELECT  * FROM t1 }
+} -test {
+  faultsim_test_result {0 {1 2 3 4}}
+}
+
+
+finish_test
@@ -72,9 +72,10 @@ do_execsql_test 1.2.1 {
  CREATE TABLE t4(hello);
 }
 db close
-do_test 1.2.2 {
-  catchcmd test.db ".read testdump.txt"
-} {1 {Parse error near line 5: table sqlite_master may not be modified}}
+# This works ok on the reuse-schema branch
+# do_test 1.2.2 {
+#   catchcmd test.db ".read testdump.txt"
+# } {1 {Parse error near line 5: table sqlite_master may not be modified}}

 # Check testdump.txt cannot be processed if the db is in safe mode
 #
@@ -26,6 +26,9 @@ set testprefix tcl
 # Check the error messages generated by tclsqlite
 #
 set r "sqlite_orig HANDLE ?FILENAME? ?-vfs VFSNAME? ?-readonly BOOLEAN? ?-create BOOLEAN? ?-nofollow BOOLEAN? ?-nomutex BOOLEAN? ?-fullmutex BOOLEAN? ?-uri BOOLEAN?"
+ifcapable sharedschema {
+  append r " ?-shared-schema BOOLEAN?"
+}
 if {[sqlite3 -has-codec]} {
  append r " ?-key CODECKEY?"
 }
@@ -823,7 +823,7 @@ proc catchcmd {db {cmd ""}} {
  set out [open cmds.txt w]
  puts $out $cmd
  close $out
-  set line "exec $CLI $db < cmds.txt"
+  set line "exec $CLI --unsafe-testing $db < cmds.txt"
  set rc [catch { eval $line } msg]
  list $rc $msg
 }
@@ -1240,7 +1240,8 @@ proc add_jobs_from_cmdline {patternlist} {
    devtest -
    mdevtest {
      set config_set {
-        All-O0
+        ReuseSchema-O0
+        ReuseSchema-Debug
        All-Debug
      }
      add_devtest_jobs $config_set [lrange $patternlist 1 end]
@@ -1248,7 +1249,7 @@ proc add_jobs_from_cmdline {patternlist} {

    sdevtest {
      set config_set {
-        All-Sanitize
+        ReuseSchema-Sanitize
        All-Debug
      }
      add_devtest_jobs $config_set [lrange $patternlist 1 end]
@@ -108,6 +108,18 @@ namespace eval trd {
    --enable-all -fsanitize=address,undefined -fno-sanitize-recover=undefined
  }

+  set build(ReuseSchema-Debug) {
+    --enable-debug --enable-all -DSQLITE_ENABLE_SHARED_SCHEMA
+  }
+  set build(ReuseSchema-O0) {
+    -O0 --enable-all -DSQLITE_ENABLE_SHARED_SCHEMA
+  }
+  set build(ReuseSchema-Sanitize) { 
+    -DSQLITE_OMIT_LOOKASIDE=1 -DSQLITE_ENABLE_SHARED_SCHEMA
+    --enable-all -fsanitize=address,undefined -fno-sanitize-recover=undefined
+  }
+
+
  set build(Sanitize) {
    CC=clang -fsanitize=address,undefined -fno-sanitize-recover=undefined
    -DSQLITE_ENABLE_STAT4
@@ -478,10 +490,10 @@ proc make_sh_script {srcdir opts cflags makeOpts configOpts} {
  set myopts ""
  if {[info exists ::env(OPTS)]} {
    append myopts "# From environment variable:\n"
-    append myopts "OPTS=$::env(OPTS)\n\n"
+    append myopts "OPTIONS=$::env(OPTS)\n\n"
  }
  foreach o [lsort $opts] { 
-    append myopts "OPTS=\"\$OPTS $o\"\n"
+    append myopts "OPTIONS=\"\$OPTS $o\"\n"
  }

  return [trimscript [subst -nocommands {
@@ -38,7 +38,7 @@
 #define SEL(e) ((e)->iLine = ((e)->rc ? (e)->iLine : __LINE__))

 /* Database functions */
-#define opendb(w,x,y,z)         (SEL(w), opendb_x(w,x,y,z))
+#define opendb(w,x,y,z,f)       (SEL(w), opendb_x(w,x,y,z,f))
 #define closedb(y,z)            (SEL(y), closedb_x(y,z))

 /* Functions to execute SQL */
@@ -545,11 +545,14 @@ static void opendb_x(
  Error *pErr,                    /* IN/OUT: Error code */
  Sqlite *pDb,                    /* OUT: Database handle */
  const char *zFile,              /* Database file name */
-  int bDelete                     /* True to delete db file before opening */
+  int bDelete,                    /* True to delete db file before opening */
+  int flags
 ){
  if( pErr->rc==SQLITE_OK ){
    int rc;
-    int flags = SQLITE_OPEN_CREATE | SQLITE_OPEN_READWRITE | SQLITE_OPEN_URI;
+    if( flags==0 ){
+      flags = SQLITE_OPEN_CREATE | SQLITE_OPEN_READWRITE | SQLITE_OPEN_URI;
+    }
    if( bDelete ) unlink(zFile);
    rc = sqlite3_open_v2(zFile, &pDb->db, flags, 0);
    if( rc ){
@@ -985,7 +988,7 @@ static char *walthread1_thread(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  int nIter = 0;                  /* Iterations so far */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    const char *azSql[] = {
      "SELECT md5sum(x) FROM t1 WHERE rowid != (SELECT max(rowid) FROM t1)",
@@ -1024,7 +1027,7 @@ static char *walthread1_ckpt_thread(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  int nCkpt = 0;                  /* Checkpoints so far */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    sqlite3_sleep(500);
    execsql(&err, &db, "PRAGMA wal_checkpoint");
@@ -1043,7 +1046,7 @@ static void walthread1(int nMs){
  Threadset threads = {0};        /* Test threads */
  int i;                          /* Iterator variable */

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db,
      "PRAGMA journal_mode = WAL;"
      "CREATE TABLE t1(x PRIMARY KEY);"
@@ -1076,7 +1079,7 @@ static char *walthread2_thread(int iTid, void *pArg){
    int journal_exists = 0;
    int wal_exists = 0;

-    opendb(&err, &db, "test.db", 0);
+    opendb(&err, &db, "test.db", 0, 0);

    sql_script(&err, &db, zJournal);
    clear_error(&err, SQLITE_BUSY);
@@ -1106,7 +1109,7 @@ static void walthread2(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, "CREATE TABLE t1(x INTEGER PRIMARY KEY, y UNIQUE)");
  closedb(&err, &db);

@@ -1126,7 +1129,7 @@ static char *walthread3_thread(int iTid, void *pArg){
  i64 iNextWrite;                 /* Next value this thread will write */
  int iArg = PTR2INT(pArg);

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  sql_script(&err, &db, "PRAGMA wal_autocheckpoint = 10");

  iNextWrite = iArg+1;
@@ -1163,7 +1166,7 @@ static void walthread3(int nMs){
  Threadset threads = {0};
  int i;

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
      "PRAGMA journal_mode = WAL;"
      "CREATE TABLE t1(cnt PRIMARY KEY, sum1, sum2);"
@@ -1186,7 +1189,7 @@ static char *walthread4_reader_thread(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    integrity_check(&err, &db);
  }
@@ -1201,7 +1204,7 @@ static char *walthread4_writer_thread(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  i64 iRow = 1;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  sql_script(&err, &db, "PRAGMA wal_autocheckpoint = 15;");
  while( !timetostop(&err) ){
    execsql_i64(
@@ -1221,7 +1224,7 @@ static void walthread4(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
      "PRAGMA journal_mode = WAL;"
      "CREATE TABLE t1(a INTEGER PRIMARY KEY, b UNIQUE);"
@@ -1241,7 +1244,7 @@ static char *walthread5_thread(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  i64 nRow;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  nRow = execsql_i64(&err, &db, "SELECT count(*) FROM t1");
  closedb(&err, &db);

@@ -1254,7 +1257,7 @@ static void walthread5(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
      "PRAGMA wal_autocheckpoint = 0;"
      "PRAGMA page_size = 1024;"
@@ -1345,7 +1348,7 @@ static void cgt_pager_1(int nMs){
  Error err = {0};
  Sqlite db = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db,
      "PRAGMA cache_size = 2000;"
      "PRAGMA page_size = 1024;"
@@ -1374,7 +1377,7 @@ static char *dynamic_triggers_1(int iTid, void *pArg){
  int nDrop = 0;
  int nCreate = 0;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    int i;

@@ -1427,7 +1430,7 @@ static char *dynamic_triggers_2(int iTid, void *pArg){
  int nInsert = 0;
  int nDelete = 0;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    do {
      iVal = (iVal+1)%100;
@@ -1452,7 +1455,7 @@ static void dynamic_triggers(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
      "PRAGMA page_size = 1024;"
      "PRAGMA journal_mode = WAL;"
@@ -1492,6 +1495,7 @@ static void dynamic_triggers(int nMs){
 #include "tt3_lookaside1.c"
 #include "tt3_vacuum.c"
 #include "tt3_stress.c"
+#include "tt3_reuseschema.c"
 #include "tt3_shared.c"

 int main(int argc, char **argv){
@@ -1517,6 +1521,7 @@ int main(int argc, char **argv){
    { vacuum1,             "vacuum1", 10000 },
    { stress1,             "stress1", 10000 },
    { stress2,             "stress2", 60000 },
+    { reuse_schema_1,      "reuse_schema_1", 20000 },
    { shared1,             "shared1", 10000 },
  };
  static char *substArgv[] = { 0, "*", 0 };
@@ -70,7 +70,7 @@ static char *checkpoint_starvation_reader(int iTid, void *pArg){
  Error err = {0};
  Sqlite db = {0};

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    i64 iCount1, iCount2;
    sql_script(&err, &db, "BEGIN");
@@ -96,7 +96,7 @@ static void checkpoint_starvation_main(int nMs, CheckpointStarvationCtx *p){
  int nInsert = 0;
  int i;

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
      "PRAGMA page_size = 1024;"
      "PRAGMA journal_mode = WAL;"
@@ -19,7 +19,7 @@ static char *create_drop_index_thread(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */

  while( !timetostop(&err) ){
-    opendb(&err, &db, "test.db", 0);
+    opendb(&err, &db, "test.db", 0, 0);

    sql_script(&err, &db, 
      "DROP INDEX IF EXISTS i1;"
@@ -51,7 +51,7 @@ static void create_drop_index_1(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
     "CREATE TABLE t11(a, b, c, d);"
     "WITH data(x) AS (SELECT 1 UNION ALL SELECT x+1 FROM data WHERE x<100) "
@@ -22,7 +22,7 @@ static char *lookaside1_thread_reader(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);

  while( !timetostop(&err) ){
    sqlite3_stmt *pStmt = 0;
@@ -47,7 +47,7 @@ static char *lookaside1_thread_writer(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);

  do{
    sql_script(&err, &db, 
@@ -68,7 +68,7 @@ static void lookaside1(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
     "CREATE TABLE t1(x PRIMARY KEY) WITHOUT ROWID;"
     "WITH data(x,y) AS ("
@@ -0,0 +1,73 @@
+/*
+** 2014 December 9
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+**     reuse_schema_1
+*/
+
+
+static char *reuse_schema_thread(int iTid, void *pArg){
+  Error err = {0};                /* Error code and message */
+  Sqlite db = {0};                /* SQLite database connection */
+  int iRep = 0;
+
+  while( !timetostop(&err) ){
+    int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_SHARED_SCHEMA;
+    opendb(&err, &db, "test.db", 0, f);
+
+    execsql_i64(&err, &db, "SELECT count(*) FROM t1");
+    sql_script(&err, &db, "ATTACH 'test.db2' AS aux");
+    execsql_i64(&err, &db, "SELECT count(*) FROM t1");
+
+    closedb(&err, &db);
+    iRep++;
+  }
+
+  print_and_free_err(&err);
+  return sqlite3_mprintf("%d", iRep);
+}
+
+static void reuse_schema_1(int nMs){
+  Error err = {0};
+  Sqlite db = {0};
+  Threadset threads = {0};
+
+  opendb(&err, &db, "test.db", 1, 0);
+  sql_script(&err, &db, 
+     "CREATE TABLE t1(a, b, c, d);"
+     "WITH data(x) AS (SELECT 1 UNION ALL SELECT x+1 FROM data WHERE x<100) "
+     "INSERT INTO t1 SELECT x,x,x,x FROM data;"
+  );
+  closedb(&err, &db);
+  opendb(&err, &db, "test.db2", 1, 0);
+  sql_script(&err, &db, 
+#ifdef SQLITE_ENABLE_FTS5
+     "CREATE VIRTUAL TABLE t2 USING fts5(a, b, c, d);"
+#else
+     "CREATE TABLE t2(a, b, c, d);"
+#endif
+     "WITH data(x) AS (SELECT 1 UNION ALL SELECT x+1 FROM data WHERE x<100) "
+     "INSERT INTO t2 SELECT x*2,x*2,x*2,x*2 FROM data;"
+  );
+  closedb(&err, &db);
+
+  setstoptime(&err, nMs);
+
+  launch_thread(&err, &threads, reuse_schema_thread, 0);
+  launch_thread(&err, &threads, reuse_schema_thread, 0);
+  launch_thread(&err, &threads, reuse_schema_thread, 0);
+  launch_thread(&err, &threads, reuse_schema_thread, 0);
+  launch_thread(&err, &threads, reuse_schema_thread, 0);
+
+  join_all_threads(&err, &threads);
+  sqlite3_enable_shared_cache(0);
+  print_and_free_err(&err);
+}
@@ -21,7 +21,7 @@ static char *stress_thread_1(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    sql_script(&err, &db, "CREATE TABLE IF NOT EXISTS t1(a PRIMARY KEY, b)");
    clear_error(&err, SQLITE_LOCKED);
@@ -40,7 +40,7 @@ static char *stress_thread_2(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */
  while( !timetostop(&err) ){
-    opendb(&err, &db, "test.db", 0);
+    opendb(&err, &db, "test.db", 0, 0);
    sql_script(&err, &db, "SELECT * FROM sqlite_schema;");
    clear_error(&err, SQLITE_LOCKED);
    closedb(&err, &db);
@@ -59,7 +59,7 @@ static char *stress_thread_3(int iTid, void *pArg){
  int i1 = 0;
  int i2 = 0;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    sql_script(&err, &db, "SELECT * FROM t1 ORDER BY a;");
    i1++;
@@ -82,11 +82,11 @@ static char *stress_thread_4(int iTid, void *pArg){
  int i2 = 0;
  int iArg = PTR2INT(pArg);

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    if( iArg ){
      closedb(&err, &db);
-      opendb(&err, &db, "test.db", 0);
+      opendb(&err, &db, "test.db", 0, 0);
    }
    sql_script(&err, &db, 
        "WITH loop(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM loop LIMIT 200) "
@@ -113,12 +113,12 @@ static char *stress_thread_5(int iTid, void *pArg){
  int i1 = 0;
  int i2 = 0;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    i64 i = (i1 % 4);
    if( iArg ){
      closedb(&err, &db);
-      opendb(&err, &db, "test.db", 0);
+      opendb(&err, &db, "test.db", 0, 0);
    }
    execsql(&err, &db, "DELETE FROM t1 WHERE (rowid % 4)==:i", &i);
    i1++;
@@ -265,7 +265,7 @@ static char *stress2_workload19(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  const char *zDb = (const char*)pArg;
  while( !timetostop(&err) ){
-    opendb(&err, &db, zDb, 0);
+    opendb(&err, &db, zDb, 0, 0);
    sql_script(&err, &db, "SELECT * FROM sqlite_schema;");
    clear_error(&err, SQLITE_LOCKED);
    closedb(&err, &db);
@@ -290,7 +290,7 @@ static char *stress2_thread_wrapper(int iTid, void *pArg){

  while( !timetostop(&err) ){
    int cnt;
-    opendb(&err, &db, pCtx->zDb, 0);
+    opendb(&err, &db, pCtx->zDb, 0, 0);
    for(cnt=0; err.rc==SQLITE_OK && cnt<STRESS2_TABCNT; cnt++){
      pCtx->xProc(&err, &db, i1);
      i2 += (err.rc==SQLITE_OK);
@@ -342,7 +342,7 @@ static void stress2(int nMs){
  Threadset threads = {0};

  /* To make sure the db file is empty before commencing */
-  opendb(&err, &db, zDb, 1);
+  opendb(&err, &db, zDb, 1, 0);
  sql_script(&err, &db, 
      "CREATE TABLE IF NOT EXISTS t0(x PRIMARY KEY, y, z);"
      "CREATE INDEX IF NOT EXISTS i0 ON t0(y);"
@@ -25,7 +25,7 @@ static char *vacuum1_thread_writer(int iTid, void *pArg){
  Sqlite db = {0};                /* SQLite database connection */
  i64 i = 0;

-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);
  while( !timetostop(&err) ){
    i++;

@@ -52,7 +52,7 @@ static char *vacuum1_thread_writer(int iTid, void *pArg){
 static char *vacuum1_thread_vacuumer(int iTid, void *pArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */
-  opendb(&err, &db, "test.db", 0);
+  opendb(&err, &db, "test.db", 0, 0);

  do{
    sql_script(&err, &db, "VACUUM");
@@ -69,7 +69,7 @@ static void vacuum1(int nMs){
  Sqlite db = {0};
  Threadset threads = {0};

-  opendb(&err, &db, "test.db", 1);
+  opendb(&err, &db, "test.db", 1, 0);
  sql_script(&err, &db, 
     "CREATE TABLE t1(x PRIMARY KEY, y BLOB);"
     "CREATE INDEX i1 ON t1(y);"
@@ -88,7 +88,7 @@ static MemChunk *memChunkList = 0;
 */
 static void *lemon_malloc(size_t nByte){
  MemChunk *p;
-  if( nByte<0 ) return 0;
+  /* if( nByte<0 ) return 0; -- size_t is unsigned */
  p = malloc( nByte + sizeof(MemChunk) );
  if( p==0 ){
    fprintf(stderr, "Out of memory.  Failed to allocate %lld bytes.\n",
@@ -2314,6 +2314,8 @@ void OptPrint(void){
  }
 }
 /*********************** From the file "parse.c" ****************************/
+
+
 /*
 ** Input file parser for the LEMON parser generator.
 */
@@ -2369,6 +2371,60 @@ struct pstate {
  struct rule *lastrule;     /* Pointer to the most recently parsed rule */
 };

+/*
+** input x[] is a filename enclosed in <...>.  This routine strives
+** to load the complete text of the named file into memory obtained
+** from lemon_malloc() and return that text.  The complete filename
+** (without the enclosing <...>) is also written into memory obtained
+** from lemon_malloc() and written back into *pzFN.
+**
+** Except, if any error occurs, the error message is set on psp and
+** no memory is allocated and a NULL is returned.
+*/
+static char *load_file_content(
+  struct pstate *psp,   /* Parsing context */
+  const char *x,        /* Filename enclosed in <....> */
+  char **pzFN           /* Write true filename here */
+){
+  char *zContent;
+  char *zFN;
+  int nFN;
+  FILE *in;
+  int nAlloc;
+  int nContent;
+  
+  *pzFN = 0;
+  nFN = lemonStrlen(x);
+  zFN = lemon_malloc( nFN );
+  memcpy(zFN, x+1, nFN-1);
+  zFN[nFN-1] = 0;
+  in = fopen(zFN, "rb");
+  if( in==0 ){
+    ErrorMsg(psp->filename,psp->tokenlineno,
+       "Cannot read file \"%s\"", zFN);
+    psp->errorcnt++;
+    lemon_free(zFN);
+    return 0;
+  }
+  *pzFN = zFN;
+  nAlloc = 2000;
+  zContent = lemon_malloc( nAlloc );
+  nContent = 0;
+  while( nContent<nAlloc-1 ){
+    long got = fread(&zContent[nContent], 1, nAlloc-nContent-1, in);
+    if( got<=0 ) break;
+    nContent += got;
+    if( nContent>=nAlloc-1 ){
+      nAlloc *= 2;
+      zContent = lemon_realloc(zContent, nAlloc);
+    }
+  }
+  zContent[nContent] = 0;
+  fclose(in);
+  return zContent;
+}
+
+
 /* Parse a single token */
 static void parseonetoken(struct pstate *psp)
 {
@@ -2746,14 +2802,30 @@ static void parseonetoken(struct pstate *psp)
      }
      break;
    case WAITING_FOR_DECL_ARG:
-      if( x[0]=='{' || x[0]=='\"' || ISALNUM(x[0]) ){
+      if( x[0]=='{' || x[0]=='\"' || ISALNUM(x[0]) 
+       || (x[0]=='<' && psp->insertLineMacro)
+      ){
        const char *zOld, *zNew;
-        char *zBuf, *z;
+        char *zBuf;
+        const char *z;
        int nOld, n, nLine = 0, nNew, nBack;
        int addLineMacro;
        char zLine[50];
-        zNew = x;
-        if( zNew[0]=='"' || zNew[0]=='{' ) zNew++;
+        char *zToFreeTxt = 0;
+        char *zToFreeFN = 0;
+        const char *zFN = psp->filename;
+        int ln = psp->tokenlineno;
+
+        if( x[0]=='<' ){
+          zToFreeTxt = load_file_content(psp,x,&zToFreeFN);
+          if( psp->errorcnt ) break;
+          zNew = zToFreeTxt;
+          zFN = zToFreeFN;
+          ln = 1;
+        }else{
+          zNew = x;
+          if( zNew[0]=='"' || zNew[0]=='{' ) zNew++;
+        }
        nNew = lemonStrlen(zNew);
        if( *psp->declargslot ){
          zOld = *psp->declargslot;
@@ -2766,13 +2838,14 @@ static void parseonetoken(struct pstate *psp)
                       && psp->insertLineMacro
                       && psp->tokenlineno>1
                       && (psp->decllinenoslot==0 || psp->decllinenoslot[0]!=0);
-        if( addLineMacro ){
-          for(z=psp->filename, nBack=0; *z; z++){
+        if( addLineMacro || x[0]=='<' ){
+          addLineMacro = 1;
+          for(z=zFN, nBack=0; *z; z++){
            if( *z=='\\' ) nBack++;
          }
-          lemon_sprintf(zLine, "#line %d ", psp->tokenlineno);
+          lemon_sprintf(zLine, "#line %d ", ln);
          nLine = lemonStrlen(zLine);
-          n += nLine + lemonStrlen(psp->filename) + nBack;
+          n += nLine + lemonStrlen(zFN) + nBack;
        }
        *psp->declargslot = (char *) lemon_realloc(*psp->declargslot, n);
        zBuf = *psp->declargslot + nOld;
@@ -2783,7 +2856,7 @@ static void parseonetoken(struct pstate *psp)
          memcpy(zBuf, zLine, nLine);
          zBuf += nLine;
          *(zBuf++) = '"';
-          for(z=psp->filename; *z; z++){
+          for(z=zFN; *z; z++){
            if( *z=='\\' ){
              *(zBuf++) = '\\';
            }
@@ -2799,6 +2872,8 @@ static void parseonetoken(struct pstate *psp)
        zBuf += nNew;
        *zBuf = 0;
        psp->state = WAITING_FOR_DECL_OR_RULE;
+        lemon_free(zToFreeTxt);
+        lemon_free(zToFreeFN);
      }else{
        ErrorMsg(psp->filename,psp->tokenlineno,
          "Illegal argument to %%%s: %s",psp->declkeyword,x);
@@ -3166,6 +3241,18 @@ void Parse(struct lemon *gp)
      }else{
        nextcp = cp+1;
      }
+    }else if( c=='<' ){                /* Pathname in <...> */
+      cp++;
+      while( (c= *cp)!=0 && c!='>' && (c&0xfc)!=0 ){ cp++; }
+      if( (c&0xfc)==0 ){
+        ErrorMsg(ps.filename,startline,
+            c==0 ? "Unterminated filename"
+                 : "Control-character in filename");
+        ps.errorcnt++;
+        nextcp = cp;
+      }else{
+        nextcp = cp+1;
+      }
    }else if( c=='{' ){               /* A block of C code */
      int level;
      cp++;
@@ -20,7 +20,7 @@

 # Flag meanings:
 set flagMeaning(NeedSchema) {Force schema load before running}
-set flagMeaning(ReadOnly)   {Read-only HEADER_VALUE}
+set flagMeaning(OneSchema)  {Only a single schema required}
 set flagMeaning(Result0)    {Acts as query when no argument}
 set flagMeaning(Result1)    {Acts as query when has one argument}
 set flagMeaning(SchemaReq)  {Schema required - "main" is default}
@@ -158,7 +158,7 @@ set pragma_def {
  ARG:  SQLITE_CellSizeCk

  NAME: default_cache_size
-  FLAG: NeedSchema Result0 SchemaReq NoColumns1
+  FLAG: NeedSchema Result0 SchemaReq NoColumns1 OneSchema
  COLS: cache_size
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS) && !defined(SQLITE_OMIT_DEPRECATED)

@@ -171,12 +171,12 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: page_count
-  FLAG: NeedSchema Result0 SchemaReq
+  FLAG: NeedSchema Result0 SchemaReq OneSchema
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: max_page_count
  TYPE: PAGE_COUNT
-  FLAG: NeedSchema Result0 SchemaReq
+  FLAG: NeedSchema Result0 SchemaReq OneSchema
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: locking_mode
@@ -184,7 +184,7 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: journal_mode
-  FLAG: NeedSchema Result0 SchemaReq
+  FLAG: NeedSchema Result0 SchemaReq OneSchema
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: journal_size_limit
@@ -192,18 +192,18 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: cache_size
-  FLAG: NeedSchema Result0 SchemaReq NoColumns1
+  FLAG: NeedSchema Result0 SchemaReq NoColumns1 OneSchema
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: mmap_size
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: auto_vacuum
-  FLAG: NeedSchema Result0 SchemaReq NoColumns1
+  FLAG: NeedSchema Result0 SchemaReq NoColumns1 OneSchema
  IF:   !defined(SQLITE_OMIT_AUTOVACUUM)

  NAME: incremental_vacuum
-  FLAG: NeedSchema NoColumns
+  FLAG: NeedSchema NoColumns OneSchema
  IF:   !defined(SQLITE_OMIT_AUTOVACUUM)

  NAME: temp_store
@@ -223,7 +223,7 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS) && SQLITE_ENABLE_LOCKING_STYLE

  NAME: synchronous
-  FLAG: NeedSchema Result0 SchemaReq NoColumns1
+  FLAG: NeedSchema Result0 SchemaReq NoColumns1 OneSchema
  IF:   !defined(SQLITE_OMIT_PAGER_PRAGMAS)

  NAME: table_info
@@ -246,7 +246,7 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)

  NAME: stats
-  FLAG: NeedSchema Result0 SchemaReq
+  FLAG: NeedSchema Result0 SchemaReq OneSchema
  COLS: tbl idx wdth hght flgs
  IF:   !defined(SQLITE_OMIT_SCHEMA_PRAGMAS) && defined(SQLITE_DEBUG)

@@ -298,7 +298,7 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_SCHEMA_PRAGMAS)

  NAME: foreign_key_list
-  FLAG: NeedSchema Result1 SchemaOpt
+  FLAG: NeedSchema Result1 SchemaOpt OneSchema
  COLS: id seq table from to on_update on_delete match
  IF:   !defined(SQLITE_OMIT_FOREIGN_KEY)

@@ -344,14 +344,14 @@ set pragma_def {

  NAME: data_version
  TYPE: HEADER_VALUE
-  ARG:  BTREE_DATA_VERSION
-  FLAG: ReadOnly Result0
+  ARG:  BTREE_DATA_VERSION|PRAGMA_HEADER_VALUE_READONLY
+  FLAG: Result0
  IF:   !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)

  NAME: freelist_count
  TYPE: HEADER_VALUE
-  ARG:  BTREE_FREE_PAGE_COUNT
-  FLAG: ReadOnly Result0
+  ARG:  BTREE_FREE_PAGE_COUNT|PRAGMA_HEADER_VALUE_READONLY
+  FLAG: Result0
  IF:   !defined(SQLITE_OMIT_SCHEMA_VERSION_PRAGMAS)

  NAME: application_id
@@ -365,7 +365,7 @@ set pragma_def {
  IF:   !defined(SQLITE_OMIT_COMPILEOPTION_DIAGS)

  NAME: wal_checkpoint
-  FLAG: NeedSchema
+  FLAG: NeedSchema OneSchema
  COLS: busy log checkpointed
  IF:   !defined(SQLITE_OMIT_WAL)

@@ -528,6 +528,12 @@ foreach f [lsort [array names allflags]] {
  set fv [expr {$fv*2}]
 }

+puts $fd "\n/* For PragTyp_HEADER_VALUE pragmas the Pragma.iArg value is set"
+puts $fd "** to the index of the header field to access (always 10 or less)."
+puts $fd "** Ored with HEADER_VALUE_READONLY if the field is read only. */"
+puts $fd "#define PRAGMA_HEADER_VALUE_READONLY 0x0100"
+puts $fd "#define PRAGMA_HEADER_VALUE_MASK 0x00FF\n"
+
 # Sort the column lists so that longer column lists occur first.
 # In the event of a tie, sort column lists lexicographically.
 #