Try to make pcache1TruncateUnsafe() run faster for the case where iLimit is

very close to iMaxKey.

FossilOrigin-Name: 9ab53605d562a926c5620cba9dc96a3b812a432f

ext/rtree/rtree6.test

@@ -102,7 +102,7 @@ do_eqp_test rtree6.2.4.2 {
   SELECT * FROM t1,t2 WHERE v=10 and x1<10 and x2>10
 } {
   0 0 0 {SCAN TABLE t1 VIRTUAL TABLE INDEX 2:C0E1} 
-  0 1 1 {SEARCH TABLE t2 USING AUTOMATIC COVERING INDEX (v=?)}
+  0 1 1 {SEARCH TABLE t2 USING AUTOMATIC PARTIAL COVERING INDEX (v=?)}
 }
 
 do_eqp_test rtree6.2.5 {

manifest

@@ -1,5 +1,5 @@
-C Take\ssteps\sto\savoid\smisestimating\srange\squery\scosts\sbased\son\sSTAT4\sdata\ndue\sto\sthe\sroundoff\serror\sof\sconverting\sfrom\sintegers\sto\sLogEst\sand\sback\nto\sintegers.
-D 2014-10-22T15:27:05.734
+C Try\sto\smake\spcache1TruncateUnsafe()\srun\sfaster\sfor\sthe\scase\swhere\siLimit\sis\nvery\sclose\sto\siMaxKey.
+D 2016-08-10T03:35:50.389
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in cf57f673d77606ab0f2d9627ca52a9ba1464146a
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -130,7 +130,7 @@ F ext/rtree/rtree2.test acbb3a4ce0f4fbc2c304d2b4b784cfa161856bba
 F ext/rtree/rtree3.test a494da55c30ee0bc9b01a91c80c81b387b22d2dc
 F ext/rtree/rtree4.test c8fe384f60ebd49540a5fecc990041bf452eb6e0
 F ext/rtree/rtree5.test 6a510494f12454bf57ef28f45bc7764ea279431e
-F ext/rtree/rtree6.test 0cfbdf27ee086bf16a3da2c6f2d5b3d6473cb27e
+F ext/rtree/rtree6.test 773a90db2dce6a8353dd0d5b64bca69b29761196
 F ext/rtree/rtree7.test 1fa710b9e6bf997a0c1a537b81be7bb6fded1971
 F ext/rtree/rtree8.test db79c812f9e4a11f9b1f3f9934007884610a713a
 F ext/rtree/rtree9.test d86ebf08ff6328895613ed577dd8a2a37c472c34
@@ -166,13 +166,13 @@ F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 3d8b83c91651f53472ca17599dae3457b8b89494
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
 F src/alter.c ba266a779bc7ce10e52e59e7d3dc79fa342e8fdb
-F src/analyze.c 567c94b763b67f7abda06dbf0ba34b0343ed9447
+F src/analyze.c afbcca663c3f3625340b8e30d440cd7a97ded6bc
 F src/attach.c f4e94df2d1826feda65eb0939f7f6f5f923a0ad9
 F src/auth.c d8abcde53426275dab6243b441256fcd8ccbebb2
 F src/backup.c a31809c65623cc41849b94d368917f8bb66e6a7e
 F src/bitvec.c 19a4ba637bd85f8f63fc8c9bae5ade9fb05ec1cb
 F src/btmutex.c 49ca66250c7dfa844a4d4cb8272b87420d27d3a5
-F src/btree.c 1b1123cba0c65caa0baa51e71b8c089e3167c3ed
+F src/btree.c 44c34502f17681eb957149cc1b8b4e1964ed231a
 F src/btree.h a79aa6a71e7f1055f01052b7f821bd1c2dce95c8
 F src/btreeInt.h 026d0129724e8f265fdc60d44ec240cf5a4e6179
 F src/build.c 9dc2bd94347b878c89627000c92b0c8d97ec2919
@@ -181,7 +181,7 @@ F src/complete.c 535183afb3c75628b78ce82612931ac7cdf26f14
 F src/ctime.c bb434068b5308a857b181c2d204a320ff0d6c638
 F src/date.c 57a7f9ba9f6b4d5268f5e411739066a611f99036
 F src/delete.c fae81cc2eb14b75267d4f47d3cfc9ae02aae726f
-F src/expr.c fc204d08af06437ddaffe5a1b1f1f6f9e1a55d6d
+F src/expr.c 0391a657df4959eaf2a2fd7d77de5ebe750686ee
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c da985ae673efef2c712caef825a5d2edb087ead7
 F src/func.c ba47c1671ab3cfdafa6e9d6ee490939ea578adee
@@ -194,7 +194,7 @@ F src/journal.c b4124532212b6952f42eb2c12fa3c25701d8ba8d
 F src/legacy.c ba1863ea58c4c840335a84ec276fc2b25e22bc4e
 F src/lempar.c 7274c97d24bb46631e504332ccd3bd1b37841770
 F src/loadext.c de741e66e5ddc1598d904d7289239696e40ed994
-F src/main.c bbe872b0ac0007bed0ebe1936fc493b039ad4f51
+F src/main.c 8207ece1b4005b1efab55d1505d8ffb45bfced05
 F src/malloc.c 3c3ac67969612493d435e14b6832793209afd2ec
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c faf615aafd8be74a71494dfa027c113ea5c6615f
@@ -215,29 +215,29 @@ F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
 F src/os_unix.c fb587121840f690101336879adfa6d0b2cd0e8c7
 F src/os_win.c a019caaae2bcbbc0cc4c39af6e7d7e43d8426053
 F src/os_win.h 09e751b20bbc107ffbd46e13555dc73576d88e21
-F src/pager.c a98547ad9b1b5dbbc5e7d1c520be041b5d2c0926
-F src/pager.h ffd5607f7b3e4590b415b007a4382f693334d428
+F src/pager.c 8d97b3633f098fef817656dcbf167ca904511d78
+F src/pager.h d1eee3c3f741be247ce6d82752a178515fc8578b
 F src/parse.y 5dfead8aed90cb0c7c1115898ee2266804daff45
 F src/pcache.c 4121a0571c18581ee9f82f086d5e2030051ebd6a
 F src/pcache.h 9b559127b83f84ff76d735c8262f04853be0c59a
-F src/pcache1.c e412cb585f777c840ddce0500eddc5c6043c2bb5
+F src/pcache1.c 04279e6cf595ba3520707886e1f4e3a0b6312cad
 F src/pragma.c 3f3e959390a10c0131676f0e307acce372777e0f
 F src/prepare.c 6ef0cf2f9274982988ed6b7cab1be23147e94196
-F src/printf.c 6b79bbd063dcbadca4cf617a4cde255bcc13ea64
+F src/printf.c 090fac0f779c93c8a95089a125339686648835e4
 F src/random.c d10c1f85b6709ca97278428fd5db5bbb9c74eece
-F src/resolve.c a3466128b52a86c466e47ac1a19e2174f7b5cf89
+F src/resolve.c 4965007d6497b6a4d7a6d98751cc39712885f952
 F src/rowset.c eccf6af6d620aaa4579bd3b72c1b6395d9e9fa1e
 F src/select.c 428165951748151e87a15295b7357221433e311b
 F src/shell.c 282f8f5278e0c78eb442217531172ec9e1538796
 F src/sqlite.h.in 4a5e5158c189d2bcd45c7c4607c2c0eb6d25c153
 F src/sqlite3.rc 992c9f5fb8285ae285d6be28240a7e8d3a7f2bad
 F src/sqlite3ext.h 17d487c3c91b0b8c584a32fbeb393f6f795eea7d
-F src/sqliteInt.h d6d423b0f62846eb441236bc15417aeede2ebbdc
+F src/sqliteInt.h c5d6a3bd2f2514ed08e3b842201b211ad3795d25
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 961d5926e5a8fda611d385ec22c226b8635cd1cb
 F src/table.c 2e99ef7ef16187e17033d9398dc962ce22dab5cb
 F src/tclsqlite.c c67d310c833046cccc192125d64ad422ab882684
-F src/test1.c 518db4305d76b29dd9da3f022ca899c8fcdf9fc7
+F src/test1.c 63d4b1707c4052cf9c05c1cbb4a62666d70a0b48
 F src/test2.c 98049e51a17dc62606a99a9eb95ee477f9996712
 F src/test3.c 1c0e5d6f080b8e33c1ce8b3078e7013fdbcd560c
 F src/test4.c 9b32d22f5f150abe23c1830e2057c4037c45b3df
@@ -302,8 +302,8 @@ F src/vtab.c cb0c194303fea276b48d7d4b6d970b5a96bde8de
 F src/wal.c 10e7de7ce90865a68153f001a61f1d985cd17983
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c c253b95b4ee44b21c406e2a1052636c31ea27804
-F src/where.c 5099c42e24c63969b3cf3b52e18c1a36cb841a34
-F src/whereInt.h 4b459cdbfc9b01f5f27673a35f9967e4dea917e8
+F src/where.c 4ce8c4826b7f86d080f0ed4e7a9045bb5014be77
+F src/whereInt.h 19279cd0664ce1d90b9ad3ef0108cb494acfe455
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test b35b4cd69fc913f90d39a575e171e1116c3a4bb7
@@ -346,6 +346,7 @@ F test/autoinc.test c58912526998a39e11f66b533e23cfabea7f25b7
 F test/autoindex1.test 6ff78b94f43a59616c06c11c55b12935173506d7
 F test/autoindex2.test 60d2fc6f38364308ce73a9beb01b47ded38697de
 F test/autoindex3.test 8254f689c3241081fad52b7bea18ba53e07e14a2
+F test/autoindex4.test fc807f9efd158bec60f5dfdf34ebe46fb274612d
 F test/autovacuum.test 941892505d2c0f410a0cb5970dfa1c7c4e5f6e74
 F test/autovacuum_ioerr2.test 8a367b224183ad801e0e24dcb7d1501f45f244b4
 F test/avtrans.test 0252654f4295ddda3b2cce0e894812259e655a85
@@ -465,6 +466,7 @@ F test/e_select2.test aceb80ab927d46fba5ce7586ebabf23e2bb0604f
 F test/e_update.test 312cb8f5ccfe41515a6bb092f8ea562a9bd54d52
 F test/e_uri.test 5ae33760fb2039c61aa2d90886f1664664173585
 F test/e_vacuum.test 5bfbdc21b65c0abf24398d0ba31dc88d93ca77a9
+F test/e_wal.test 0967f0b8f1dfda871dc7b9b5574198f1f4f7d69a
 F test/enc.test e54531cd6bf941ee6760be041dff19a104c7acea
 F test/enc2.test 83437a79ba1545a55fb549309175c683fb334473
 F test/enc3.test 90683ad0e6ea587b9d5542ca93568af9a9858c40
@@ -1205,7 +1207,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 3e922208b68563489c7766abb9afb4885113e7b8
-R 5c508733aebac553de79291a7eabd709
+P 5980e625dbb694dc3b0535e71fd986a6d211e245
+R 2aecde0e663e22b28208114fb4e83a67
 U drh
-Z a3d7104c7f173585d7e788d6453aa065
+Z 9f57a23eafe4610b0bd9a6ac18d687c6

manifest.uuid

@@ -1 +1 @@
-3c933bf95f291f7957580d823dce92c981375a5c
+9ab53605d562a926c5620cba9dc96a3b812a432f

src/analyze.c

@@ -1861,7 +1861,7 @@ int sqlite3AnalysisLoad(sqlite3 *db, int iDb){
 
   /* Load the statistics from the sqlite_stat4 table. */
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
-  if( rc==SQLITE_OK ){
+  if( rc==SQLITE_OK && OptimizationEnabled(db, SQLITE_Stat34) ){
     int lookasideEnabled = db->lookaside.bEnabled;
     db->lookaside.bEnabled = 0;
     rc = loadStat4(db, sInfo.zDatabase);

src/expr.c

@@ -1210,20 +1210,24 @@ void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
 }
 
 /*
-** These routines are Walker callbacks.  Walker.u.pi is a pointer
-** to an integer.  These routines are checking an expression to see
-** if it is a constant.  Set *Walker.u.i to 0 if the expression is
-** not constant.
+** These routines are Walker callbacks used to check expressions to
+** see if they are "constant" for some definition of constant.  The
+** Walker.eCode value determines the type of "constant" we are looking
+** for.
 **
 ** These callback routines are used to implement the following:
 **
-**     sqlite3ExprIsConstant()                  pWalker->u.i==1
-**     sqlite3ExprIsConstantNotJoin()           pWalker->u.i==2
-**     sqlite3ExprIsConstantOrFunction()        pWalker->u.i==3 or 4
+**     sqlite3ExprIsConstant()                  pWalker->eCode==1
+**     sqlite3ExprIsConstantNotJoin()           pWalker->eCode==2
+**     sqlite3ExprRefOneTableOnly()             pWalker->eCode==3
+**     sqlite3ExprIsConstantOrFunction()        pWalker->eCode==4 or 5
+**
+** In all cases, the callbacks set Walker.eCode=0 and abort if the expression
+** is found to not be a constant.
 **
 ** The sqlite3ExprIsConstantOrFunction() is used for evaluating expressions
-** in a CREATE TABLE statement.  The Walker.u.i value is 4 when parsing
-** an existing schema and 3 when processing a new statement.  A bound
+** in a CREATE TABLE statement.  The Walker.eCode value is 5 when parsing
+** an existing schema and 4 when processing a new statement.  A bound
 ** parameter raises an error for new statements, but is silently converted
 ** to NULL for existing schemas.  This allows sqlite_master tables that 
 ** contain a bound parameter because they were generated by older versions
@@ -1232,23 +1236,25 @@ void sqlite3ExprListDelete(sqlite3 *db, ExprList *pList){
 */
 static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
 
-  /* If pWalker->u.i is 2 then any term of the expression that comes from
-  ** the ON or USING clauses of a join disqualifies the expression
+  /* If pWalker->eCode is 2 then any term of the expression that comes from
+  ** the ON or USING clauses of a left join disqualifies the expression
   ** from being considered constant. */
-  if( pWalker->u.i==2 && ExprHasProperty(pExpr, EP_FromJoin) ){
-    pWalker->u.i = 0;
+  if( pWalker->eCode==2 && ExprHasProperty(pExpr, EP_FromJoin) ){
+    pWalker->eCode = 0;
     return WRC_Abort;
   }
 
   switch( pExpr->op ){
     /* Consider functions to be constant if all their arguments are constant
-    ** and either pWalker->u.i==3 or 4 or the function as the SQLITE_FUNC_CONST
-    ** flag. */
+    ** and either pWalker->eCode==4 or 5 or the function has the
+    ** SQLITE_FUNC_CONST flag. */
     case TK_FUNCTION:
-      if( pWalker->u.i>=3 || ExprHasProperty(pExpr,EP_Constant) ){
+      if( pWalker->eCode>=4 || ExprHasProperty(pExpr,EP_Constant) ){
         return WRC_Continue;
+      }else{
+        pWalker->eCode = 0;
+        return WRC_Abort;
       }
-      /* Fall through */
     case TK_ID:
     case TK_COLUMN:
     case TK_AGG_FUNCTION:
@@ -1257,18 +1263,22 @@ static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
       testcase( pExpr->op==TK_COLUMN );
       testcase( pExpr->op==TK_AGG_FUNCTION );
       testcase( pExpr->op==TK_AGG_COLUMN );
-      pWalker->u.i = 0;
-      return WRC_Abort;
+      if( pWalker->eCode==3 && pExpr->iTable==pWalker->u.iCur ){
+        return WRC_Continue;
+      }else{
+        pWalker->eCode = 0;
+        return WRC_Abort;
+      }
     case TK_VARIABLE:
-      if( pWalker->u.i==4 ){
+      if( pWalker->eCode==5 ){
         /* Silently convert bound parameters that appear inside of CREATE
         ** statements into a NULL when parsing the CREATE statement text out
         ** of the sqlite_master table */
         pExpr->op = TK_NULL;
-      }else if( pWalker->u.i==3 ){
+      }else if( pWalker->eCode==4 ){
         /* A bound parameter in a CREATE statement that originates from
         ** sqlite3_prepare() causes an error */
-        pWalker->u.i = 0;
+        pWalker->eCode = 0;
         return WRC_Abort;
       }
       /* Fall through */
@@ -1280,21 +1290,22 @@ static int exprNodeIsConstant(Walker *pWalker, Expr *pExpr){
 }
 static int selectNodeIsConstant(Walker *pWalker, Select *NotUsed){
   UNUSED_PARAMETER(NotUsed);
-  pWalker->u.i = 0;
+  pWalker->eCode = 0;
   return WRC_Abort;
 }
-static int exprIsConst(Expr *p, int initFlag){
+static int exprIsConst(Expr *p, int initFlag, int iCur){
   Walker w;
   memset(&w, 0, sizeof(w));
-  w.u.i = initFlag;
+  w.eCode = initFlag;
   w.xExprCallback = exprNodeIsConstant;
   w.xSelectCallback = selectNodeIsConstant;
+  w.u.iCur = iCur;
   sqlite3WalkExpr(&w, p);
-  return w.u.i;
+  return w.eCode;
 }
 
 /*
-** Walk an expression tree.  Return 1 if the expression is constant
+** Walk an expression tree.  Return non-zero if the expression is constant
 ** and 0 if it involves variables or function calls.
 **
 ** For the purposes of this function, a double-quoted string (ex: "abc")
@@ -1302,21 +1313,31 @@ static int exprIsConst(Expr *p, int initFlag){
 ** a constant.
 */
 int sqlite3ExprIsConstant(Expr *p){
-  return exprIsConst(p, 1);
+  return exprIsConst(p, 1, 0);
 }
 
 /*
-** Walk an expression tree.  Return 1 if the expression is constant
+** Walk an expression tree.  Return non-zero if the expression is constant
 ** that does no originate from the ON or USING clauses of a join.
 ** Return 0 if it involves variables or function calls or terms from
 ** an ON or USING clause.
 */
 int sqlite3ExprIsConstantNotJoin(Expr *p){
-  return exprIsConst(p, 2);
+  return exprIsConst(p, 2, 0);
 }
 
 /*
-** Walk an expression tree.  Return 1 if the expression is constant
+** Walk an expression tree.  Return non-zero if the expression constant
+** for any single row of the table with cursor iCur.  In other words, the
+** expression must not refer to any non-deterministic function nor any
+** table other than iCur.
+*/
+int sqlite3ExprIsTableConstant(Expr *p, int iCur){
+  return exprIsConst(p, 3, iCur);
+}
+
+/*
+** Walk an expression tree.  Return non-zero if the expression is constant
 ** or a function call with constant arguments.  Return and 0 if there
 ** are any variables.
 **
@@ -1326,7 +1347,7 @@ int sqlite3ExprIsConstantNotJoin(Expr *p){
 */
 int sqlite3ExprIsConstantOrFunction(Expr *p, u8 isInit){
   assert( isInit==0 || isInit==1 );
-  return exprIsConst(p, 3+isInit);
+  return exprIsConst(p, 4+isInit, 0);
 }
 
 /*

src/main.c

@@ -2751,13 +2751,7 @@ int sqlite3_create_collation(
   void* pCtx,
   int(*xCompare)(void*,int,const void*,int,const void*)
 ){
-  int rc;
-  sqlite3_mutex_enter(db->mutex);
-  assert( !db->mallocFailed );
-  rc = createCollation(db, zName, (u8)enc, pCtx, xCompare, 0);
-  rc = sqlite3ApiExit(db, rc);
-  sqlite3_mutex_leave(db->mutex);
-  return rc;
+  return sqlite3_create_collation_v2(db, zName, enc, pCtx, xCompare, 0);
 }
 
 /*

src/pager.c

@@ -6847,6 +6847,18 @@ int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
 }
 #endif
 
+/*
+** The page handle passed as the first argument refers to a dirty page 
+** with a page number other than iNew. This function changes the page's 
+** page number to iNew and sets the value of the PgHdr.flags field to 
+** the value passed as the third parameter.
+*/
+void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
+  assert( pPg->pgno!=iNew );
+  pPg->flags = flags;
+  sqlite3PcacheMove(pPg, iNew);
+}
+
 /*
 ** Return a pointer to the data for the specified page.
 */
@@ -7245,4 +7257,5 @@ int sqlite3PagerWalFramesize(Pager *pPager){
 }
 #endif
 
+
 #endif /* SQLITE_OMIT_DISKIO */

src/pager.h

@@ -188,6 +188,8 @@ int sqlite3SectorSize(sqlite3_file *);
 /* Functions used to truncate the database file. */
 void sqlite3PagerTruncateImage(Pager*,Pgno);
 
+void sqlite3PagerRekey(DbPage*, Pgno, u16);
+
 #if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_WAL)
 void *sqlite3PagerCodec(DbPage *);
 #endif

src/pcache1.c

@@ -498,25 +498,55 @@ static void pcache1TruncateUnsafe(
   PCache1 *pCache,             /* The cache to truncate */
   unsigned int iLimit          /* Drop pages with this pgno or larger */
 ){
-  TESTONLY( unsigned int nPage = 0; )  /* To assert pCache->nPage is correct */
-  unsigned int h;
+  TESTONLY( int nPage = 0; )  /* To assert pCache->nPage is correct */
+  unsigned int h, iStop;
+  START_DEBUG_TIMER;
+  int nFree = 0;
   assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  for(h=0; h<pCache->nHash; h++){
-    PgHdr1 **pp = &pCache->apHash[h]; 
+  assert( pCache->iMaxKey >= iLimit );
+  assert( pCache->nHash > 0 );
+  if( pCache->iMaxKey - iLimit < pCache->nHash/2 ){
+    /* If we are just shaving the last few pages off the end of the
+    ** cache, then there is no point in scanning the entire hash table.
+    ** Only scan those hash slots that might contain pages that need to
+    ** be removed. */
+    iStop = iLimit % pCache->nHash;
+    h = pCache->iMaxKey % pCache->nHash;
+    TESTONLY( nPage = -10; )  /* Disable the pCache->nPage validity check */
+  }else{
+    /* This is the general case where many pages are being removed.
+    ** It is necessary to scan the entire hash table */
+    iStop = 0;
+    h = pCache->nHash - 1;
+  }
+  for(;;){
+    PgHdr1 **pp;
     PgHdr1 *pPage;
+    assert( h<pCache->nHash );
+    pp = &pCache->apHash[h]; 
     while( (pPage = *pp)!=0 ){
       if( pPage->iKey>=iLimit ){
         pCache->nPage--;
+        nFree++;
         *pp = pPage->pNext;
         if( !pPage->isPinned ) pcache1PinPage(pPage);
         pcache1FreePage(pPage);
       }else{
         pp = &pPage->pNext;
-        TESTONLY( nPage++; )
+        TESTONLY( if( nPage>=0 ) nPage++; )
       }
     }
+    if( h==iStop ) break;
+    h = h ? h-1 : pCache->nHash - 1;
+  }
+  assert( nPage<0 || pCache->nPage==(unsigned)nPage );
+  END_DEBUG_TIMER( DEBUG_TIMER_BIG_TIMEOUT ){
+    sqlite3_log(SQLITE_NOTICE, 
+       "slow pcache1TruncateUnsafe() %lld "
+       " nFree=%d nHash=%d nPage=%d iLimit=%d iMaxKey=%d",
+       iDebugTimer,
+       nFree, pCache->nHash, pCache->nPage, iLimit, pCache->iMaxKey);
   }
-  assert( pCache->nPage==nPage );
 }
 
 /******************************************************************************/
@@ -945,7 +975,7 @@ static void pcache1Destroy(sqlite3_pcache *p){
   PGroup *pGroup = pCache->pGroup;
   assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
   pcache1EnterMutex(pGroup);
-  pcache1TruncateUnsafe(pCache, 0);
+  if( pCache->nPage ) pcache1TruncateUnsafe(pCache, 0);
   assert( pGroup->nMaxPage >= pCache->nMax );
   pGroup->nMaxPage -= pCache->nMax;
   assert( pGroup->nMinPage >= pCache->nMin );

src/printf.c

@@ -21,11 +21,7 @@
 ** the glibc version so the glibc version is definitely preferred.
 */
 #if !defined(HAVE_STRCHRNUL)
-# if defined(linux)
-#  define HAVE_STRCHRNUL 1
-# else
-#  define HAVE_STRCHRNUL 0
-# endif
+# define HAVE_STRCHRNUL 0
 #endif
 
 

src/resolve.c

@@ -28,7 +28,7 @@
 ** is a helper function - a callback for the tree walker.
 */
 static int incrAggDepth(Walker *pWalker, Expr *pExpr){
-  if( pExpr->op==TK_AGG_FUNCTION ) pExpr->op2 += pWalker->u.i;
+  if( pExpr->op==TK_AGG_FUNCTION ) pExpr->op2 += pWalker->u.n;
   return WRC_Continue;
 }
 static void incrAggFunctionDepth(Expr *pExpr, int N){
@@ -36,7 +36,7 @@ static void incrAggFunctionDepth(Expr *pExpr, int N){
     Walker w;
     memset(&w, 0, sizeof(w));
     w.xExprCallback = incrAggDepth;
-    w.u.i = N;
+    w.u.n = N;
     sqlite3WalkExpr(&w, pExpr);
   }
 }
@@ -584,7 +584,7 @@ static int exprProbability(Expr *p){
   sqlite3AtoF(p->u.zToken, &r, sqlite3Strlen30(p->u.zToken), SQLITE_UTF8);
   assert( r>=0.0 );
   if( r>1.0 ) return -1;
-  return (int)(r*1000.0);
+  return (int)(r*134217728.0);
 }
 
 /*
@@ -716,7 +716,7 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
             ** EVIDENCE-OF: R-53436-40973 The likely(X) function is equivalent to
             ** likelihood(X,0.9375). */
             /* TUNING: unlikely() probability is 0.0625.  likely() is 0.9375 */
-            pExpr->iTable = pDef->zName[0]=='u' ? 62 : 938;
+            pExpr->iTable = pDef->zName[0]=='u' ? 8388608 : 125829120;
           }             
         }
 #ifndef SQLITE_OMIT_AUTHORIZATION

src/sqliteInt.h

@@ -199,7 +199,7 @@
 ** be overridden at runtime using the sqlite3_config() API.
 */
 #if !defined(SQLITE_DEFAULT_MEMSTATUS)
-# define SQLITE_DEFAULT_MEMSTATUS 1
+# define SQLITE_DEFAULT_MEMSTATUS 0
 #endif
 
 /*
@@ -1214,7 +1214,7 @@ struct sqlite3 {
 #define SQLITE_SubqCoroutine  0x0100   /* Evaluate subqueries as coroutines */
 #define SQLITE_Transitive     0x0200   /* Transitive constraints */
 #define SQLITE_OmitNoopJoin   0x0400   /* Omit unused tables in joins */
-#define SQLITE_Stat3          0x0800   /* Use the SQLITE_STAT3 table */
+#define SQLITE_Stat34         0x0800   /* Use STAT3 or STAT4 data */
 #define SQLITE_AllOpts        0xffff   /* All optimizations */
 
 /*
@@ -2000,7 +2000,7 @@ struct Expr {
   int iTable;            /* TK_COLUMN: cursor number of table holding column
                          ** TK_REGISTER: register number
                          ** TK_TRIGGER: 1 -> new, 0 -> old
-                         ** EP_Unlikely:  1000 times likelihood */
+                         ** EP_Unlikely:  134217728 times likelihood */
   ynVar iColumn;         /* TK_COLUMN: column index.  -1 for rowid.
                          ** TK_VARIABLE: variable number (always >= 1). */
   i16 iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */
@@ -2892,9 +2892,11 @@ struct Walker {
   void (*xSelectCallback2)(Walker*,Select*);/* Second callback for SELECTs */
   Parse *pParse;                            /* Parser context.  */
   int walkerDepth;                          /* Number of subqueries */
+  u8 eCode;                                 /* A small processing code */
   union {                                   /* Extra data for callback */
     NameContext *pNC;                          /* Naming context */
-    int i;                                     /* Integer value */
+    int n;                                     /* A counter */
+    int iCur;                                  /* A cursor number */
     SrcList *pSrcList;                         /* FROM clause */
     struct SrcCount *pSrcCount;                /* Counting column references */
   } u;
@@ -3295,6 +3297,7 @@ void sqlite3LeaveMutexAndCloseZombie(sqlite3*);
 int sqlite3ExprIsConstant(Expr*);
 int sqlite3ExprIsConstantNotJoin(Expr*);
 int sqlite3ExprIsConstantOrFunction(Expr*, u8);
+int sqlite3ExprIsTableConstant(Expr*,int);
 int sqlite3ExprIsInteger(Expr*, int*);
 int sqlite3ExprCanBeNull(const Expr*);
 int sqlite3ExprNeedsNoAffinityChange(const Expr*, char);
@@ -3812,4 +3815,25 @@ int sqlite3ThreadCreate(SQLiteThread**,void*(*)(void*),void*);
 int sqlite3ThreadJoin(SQLiteThread*, void**);
 #endif
 
+#include <sys/time.h>
+#define START_DEBUG_TIMER \
+  sqlite3_uint64 iDebugTimerStart, iDebugTimer;                     \
+  struct timeval debug_timer_var;                                   \
+  gettimeofday(&debug_timer_var, 0);                                \
+  iDebugTimerStart = 1000000*(sqlite3_uint64)debug_timer_var.tv_sec \
+                     + debug_timer_var.tv_usec;
+
+#define END_DEBUG_TIMER(nDebugUsec) \
+  gettimeofday(&debug_timer_var, 0);                                \
+  iDebugTimer = 1000000*(sqlite3_uint64)debug_timer_var.tv_sec      \
+                +debug_timer_var.tv_usec-iDebugTimerStart;          \
+  if( iDebugTimer>=nDebugUsec )
+
+#ifndef DEBUG_TIMER_BIG_TIMEOUT
+# define DEBUG_TIMER_BIG_TIMEOUT  10000
+#endif
+#ifndef DEBUG_TIMER_SMALL_TIMEOUT
+# define DEBUG_TIMER_SMALL_TIMEOUT 1000
+#endif
+
 #endif /* _SQLITEINT_H_ */

src/test1.c

@@ -6293,7 +6293,8 @@ static int optimization_control(
     { "transitive",          SQLITE_Transitive     },
     { "subquery-coroutine",  SQLITE_SubqCoroutine  },
     { "omit-noop-join",      SQLITE_OmitNoopJoin   },
-    { "stat3",               SQLITE_Stat3          },
+    { "stat3",               SQLITE_Stat34         },
+    { "stat4",               SQLITE_Stat34         },
   };
 
   if( objc!=4 ){

src/where.c

@@ -225,7 +225,7 @@ static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
   }
   pTerm = &pWC->a[idx = pWC->nTerm++];
   if( p && ExprHasProperty(p, EP_Unlikely) ){
-    pTerm->truthProb = sqlite3LogEst(p->iTable) - 99;
+    pTerm->truthProb = sqlite3LogEst(p->iTable) - 270;
   }else{
     pTerm->truthProb = 1;
   }
@@ -756,6 +756,15 @@ static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
   }
 }
 
+/*
+** Mark term iChild as being a child of term iParent
+*/
+static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){
+  pWC->a[iChild].iParent = iParent;
+  pWC->a[iChild].truthProb = pWC->a[iParent].truthProb;
+  pWC->a[iParent].nChild++;
+}
+
 #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
 /*
 ** Analyze a term that consists of two or more OR-connected
@@ -1053,8 +1062,7 @@ static void exprAnalyzeOrTerm(
         testcase( idxNew==0 );
         exprAnalyze(pSrc, pWC, idxNew);
         pTerm = &pWC->a[idxTerm];
-        pWC->a[idxNew].iParent = idxTerm;
-        pTerm->nChild = 1;
+        markTermAsChild(pWC, idxNew, idxTerm);
       }else{
         sqlite3ExprListDelete(db, pList);
       }
@@ -1156,9 +1164,8 @@ static void exprAnalyze(
         idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
         if( idxNew==0 ) return;
         pNew = &pWC->a[idxNew];
-        pNew->iParent = idxTerm;
+        markTermAsChild(pWC, idxNew, idxTerm);
         pTerm = &pWC->a[idxTerm];
-        pTerm->nChild = 1;
         pTerm->wtFlags |= TERM_COPIED;
         if( pExpr->op==TK_EQ
          && !ExprHasProperty(pExpr, EP_FromJoin)
@@ -1215,9 +1222,8 @@ static void exprAnalyze(
       testcase( idxNew==0 );
       exprAnalyze(pSrc, pWC, idxNew);
       pTerm = &pWC->a[idxTerm];
-      pWC->a[idxNew].iParent = idxTerm;
+      markTermAsChild(pWC, idxNew, idxTerm);
     }
-    pTerm->nChild = 2;
   }
 #endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
 
@@ -1292,9 +1298,8 @@ static void exprAnalyze(
     exprAnalyze(pSrc, pWC, idxNew2);
     pTerm = &pWC->a[idxTerm];
     if( isComplete ){
-      pWC->a[idxNew1].iParent = idxTerm;
-      pWC->a[idxNew2].iParent = idxTerm;
-      pTerm->nChild = 2;
+      markTermAsChild(pWC, idxNew1, idxTerm);
+      markTermAsChild(pWC, idxNew2, idxTerm);
     }
   }
 #endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
@@ -1327,9 +1332,8 @@ static void exprAnalyze(
       pNewTerm->leftCursor = pLeft->iTable;
       pNewTerm->u.leftColumn = pLeft->iColumn;
       pNewTerm->eOperator = WO_MATCH;
-      pNewTerm->iParent = idxTerm;
+      markTermAsChild(pWC, idxNew, idxTerm);
       pTerm = &pWC->a[idxTerm];
-      pTerm->nChild = 1;
       pTerm->wtFlags |= TERM_COPIED;
       pNewTerm->prereqAll = pTerm->prereqAll;
     }
@@ -1350,7 +1354,7 @@ static void exprAnalyze(
   if( pExpr->op==TK_NOTNULL
    && pExpr->pLeft->op==TK_COLUMN
    && pExpr->pLeft->iColumn>=0
-   && OptimizationEnabled(db, SQLITE_Stat3)
+   && OptimizationEnabled(db, SQLITE_Stat34)
   ){
     Expr *pNewExpr;
     Expr *pLeft = pExpr->pLeft;
@@ -1369,9 +1373,8 @@ static void exprAnalyze(
       pNewTerm->leftCursor = pLeft->iTable;
       pNewTerm->u.leftColumn = pLeft->iColumn;
       pNewTerm->eOperator = WO_GT;
-      pNewTerm->iParent = idxTerm;
+      markTermAsChild(pWC, idxNew, idxTerm);
       pTerm = &pWC->a[idxTerm];
-      pTerm->nChild = 1;
       pTerm->wtFlags |= TERM_COPIED;
       pNewTerm->prereqAll = pTerm->prereqAll;
     }
@@ -1591,6 +1594,8 @@ static void constructAutomaticIndex(
   Bitmask idxCols;            /* Bitmap of columns used for indexing */
   Bitmask extraCols;          /* Bitmap of additional columns */
   u8 sentWarning = 0;         /* True if a warnning has been issued */
+  Expr *pPartial = 0;         /* Partial Index Expression */
+  int iContinue = 0;          /* Jump here to skip excluded rows */
 
   /* Generate code to skip over the creation and initialization of the
   ** transient index on 2nd and subsequent iterations of the loop. */
@@ -1606,6 +1611,12 @@ static void constructAutomaticIndex(
   pLoop = pLevel->pWLoop;
   idxCols = 0;
   for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
+    if( pLoop->prereq==0
+     && (pTerm->wtFlags & TERM_VIRTUAL)==0
+     && sqlite3ExprIsTableConstant(pTerm->pExpr, pSrc->iCursor) ){
+      pPartial = sqlite3ExprAnd(pParse->db, pPartial,
+                                sqlite3ExprDup(pParse->db, pTerm->pExpr, 0));
+    }
     if( termCanDriveIndex(pTerm, pSrc, notReady) ){
       int iCol = pTerm->u.leftColumn;
       Bitmask cMask = iCol>=BMS ? MASKBIT(BMS-1) : MASKBIT(iCol);
@@ -1618,7 +1629,9 @@ static void constructAutomaticIndex(
         sentWarning = 1;
       }
       if( (idxCols & cMask)==0 ){
-        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ) return;
+        if( whereLoopResize(pParse->db, pLoop, nKeyCol+1) ){
+          goto end_auto_index_create;
+        }
         pLoop->aLTerm[nKeyCol++] = pTerm;
         idxCols |= cMask;
       }
@@ -1651,7 +1664,7 @@ static void constructAutomaticIndex(
 
   /* Construct the Index object to describe this index */
   pIdx = sqlite3AllocateIndexObject(pParse->db, nKeyCol+1, 0, &zNotUsed);
-  if( pIdx==0 ) return;
+  if( pIdx==0 ) goto end_auto_index_create;
   pLoop->u.btree.pIndex = pIdx;
   pIdx->zName = "auto-index";
   pIdx->pTable = pTable;
@@ -1703,18 +1716,29 @@ static void constructAutomaticIndex(
   VdbeComment((v, "for %s", pTable->zName));
 
   /* Fill the automatic index with content */
+  sqlite3ExprCachePush(pParse);
   addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur); VdbeCoverage(v);
+  if( pPartial ){
+    iContinue = sqlite3VdbeMakeLabel(v);
+    sqlite3ExprIfFalse(pParse, pPartial, iContinue, SQLITE_JUMPIFNULL);
+    pLoop->wsFlags |= WHERE_PARTIALIDX;
+  }
   regRecord = sqlite3GetTempReg(pParse);
   sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 0, 0, 0, 0);
   sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
   sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
+  if( pPartial ) sqlite3VdbeResolveLabel(v, iContinue);
   sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1); VdbeCoverage(v);
   sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
   sqlite3VdbeJumpHere(v, addrTop);
   sqlite3ReleaseTempReg(pParse, regRecord);
+  sqlite3ExprCachePop(pParse);
   
   /* Jump here when skipping the initialization */
   sqlite3VdbeJumpHere(v, addrInit);
+
+end_auto_index_create:
+  sqlite3ExprDelete(pParse->db, pPartial);
 }
 #endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
 
@@ -2159,7 +2183,6 @@ static int whereRangeScanEst(
 
   if( p->nSample>0
    && nEq<p->nSampleCol
-   && OptimizationEnabled(pParse->db, SQLITE_Stat3) 
   ){
     if( nEq==pBuilder->nRecValid ){
       UnpackedRecord *pRec = pBuilder->pRec;
@@ -2273,12 +2296,15 @@ static int whereRangeScanEst(
   nNew = whereRangeAdjust(pLower, nOut);
   nNew = whereRangeAdjust(pUpper, nNew);
 
-  /* TUNING: If there is both an upper and lower limit, assume the range is
+  /* TUNING: If there is both an upper and lower limit and neither limit
+  ** has an application-defined likelihood(), assume the range is
   ** reduced by an additional 75%. This means that, by default, an open-ended
   ** range query (e.g. col > ?) is assumed to match 1/4 of the rows in the
   ** index. While a closed range (e.g. col BETWEEN ? AND ?) is estimated to
   ** match 1/64 of the index. */ 
-  if( pLower && pUpper ) nNew -= 20;
+  if( pLower && pLower->truthProb>0 && pUpper && pUpper->truthProb>0 ){
+    nNew -= 20;
+  }
 
   nOut -= (pLower!=0) + (pUpper!=0);
   if( nNew<10 ) nNew = 10;
@@ -2841,6 +2867,8 @@ static void explainOneScan(
         if( isSearch ){
           zFmt = "PRIMARY KEY";
         }
+      }else if( flags & WHERE_PARTIALIDX ){
+        zFmt = "AUTOMATIC PARTIAL COVERING INDEX";
       }else if( flags & WHERE_AUTO_INDEX ){
         zFmt = "AUTOMATIC COVERING INDEX";
       }else if( flags & WHERE_IDX_ONLY ){
@@ -4422,7 +4450,6 @@ static int whereLoopAddBtreeIndex(
         if( nInMul==0 
          && pProbe->nSample 
          && pNew->u.btree.nEq<=pProbe->nSampleCol
-         && OptimizationEnabled(db, SQLITE_Stat3) 
          && ((eOp & WO_IN)==0 || !ExprHasProperty(pTerm->pExpr, EP_xIsSelect))
         ){
           Expr *pExpr = pTerm->pExpr;

src/whereInt.h

@@ -459,3 +459,4 @@ struct WhereInfo {
 #define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
 #define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
 #define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
+#define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */

test/autoindex4.test

@@ -0,0 +1,52 @@
+# 2014-10-24
+#
+# 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.
+#
+#*************************************************************************
+#
+# This file implements regression tests for SQLite library.  The
+# focus of this script is testing automatic index creation logic,
+# and specifically creation of automatic partial indexes.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+
+do_execsql_test autoindex4-1.0 {
+  CREATE TABLE t1(a,b);
+  INSERT INTO t1 VALUES(123,'abc'),(234,'def'),(234,'ghi'),(345,'jkl');
+  CREATE TABLE t2(x,y);
+  INSERT INTO t2 VALUES(987,'zyx'),(654,'wvu'),(987,'rqp');
+
+  SELECT *, '|' FROM t1, t2 WHERE a=234 AND x=987 ORDER BY +b;
+} {234 def 987 rqp | 234 def 987 zyx | 234 ghi 987 rqp | 234 ghi 987 zyx |}
+do_execsql_test autoindex4-1.1 {
+  SELECT *, '|' FROM t1, t2 WHERE a=234 AND x=555;
+} {}
+
+do_execsql_test autoindex4-1.2 {
+  SELECT *, '|' FROM t1 LEFT JOIN t2 ON a=234 AND x=555;
+} {123 abc {} {} | 234 def {} {} | 234 ghi {} {} | 345 jkl {} {} |}
+do_execsql_test autoindex4-1.3 {
+  SELECT *, '|' FROM t1 LEFT JOIN t2 ON x=555 WHERE a=234;
+} {234 def {} {} | 234 ghi {} {} |}
+do_execsql_test autoindex4-1.4 {
+  SELECT *, '|' FROM t1 LEFT JOIN t2 WHERE a=234 AND x=555;
+} {}
+
+
+do_execsql_test autoindex4-2.0 {
+  CREATE TABLE t3(e,f);
+  INSERT INTO t3 VALUES(123,654),(555,444),(234,987);
+
+  SELECT (SELECT count(*) FROM t1, t2 WHERE a=e AND x=f), e, f, '|'
+    FROM t3
+   ORDER BY rowid;
+} {1 123 654 | 0 555 444 | 4 234 987 |}
+
+finish_test

test/e_wal.test

@@ -0,0 +1,229 @@
+# 2011 May 06
+#
+# 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 e_wal
+
+db close
+testvfs oldvfs -iversion 1
+
+
+# EVIDENCE-OF: R-58297-14483 WAL databases can be created, read, and
+# written even if shared memory is unavailable as long as the
+# locking_mode is set to EXCLUSIVE before the first attempted access.
+#
+# EVIDENCE-OF: R-00449-33772 This feature allows WAL databases to be
+# created, read, and written by legacy VFSes that lack the "version 2"
+# shared-memory methods xShmMap, xShmLock, xShmBarrier, and xShmUnmap on
+# the sqlite3_io_methods object.
+#
+# 1.1: "create" tests.
+# 1.2: "read" tests.
+# 1.3: "write" tests.
+#
+# All three done with VFS "oldvfs", which has iVersion==1 and so does
+# not support shared memory.
+# 
+sqlite3 db test.db -vfs oldvfs
+do_execsql_test 1.1.1 {
+  PRAGMA journal_mode = WAL;
+} {delete}
+do_execsql_test 1.1.2 {
+  PRAGMA locking_mode = EXCLUSIVE;
+  PRAGMA journal_mode = WAL;
+} {exclusive wal}
+do_execsql_test 1.1.3 {
+  CREATE TABLE t1(x, y);
+  INSERT INTO t1 VALUES(1, 2);
+} {}
+do_test 1.1.4 {
+  list [file exists test.db-shm] [file exists test.db-wal]
+} {0 1}
+
+do_test 1.2.1 {
+  db close
+  sqlite3 db test.db -vfs oldvfs
+  catchsql { SELECT * FROM t1 }
+} {1 {unable to open database file}}
+do_test 1.2.2 {
+  execsql { PRAGMA locking_mode = EXCLUSIVE }
+  execsql { SELECT * FROM t1 }
+} {1 2}
+do_test 1.2.3 {
+  list [file exists test.db-shm] [file exists test.db-wal]
+} {0 1}
+
+do_test 1.3.1 {
+  db close
+  sqlite3 db test.db -vfs oldvfs
+  catchsql { INSERT INTO t1 VALUES(3, 4) }
+} {1 {unable to open database file}}
+do_test 1.3.2 {
+  execsql { PRAGMA locking_mode = EXCLUSIVE }
+  execsql { INSERT INTO t1 VALUES(3, 4) }
+  execsql { SELECT * FROM t1 }
+} {1 2 3 4}
+do_test 1.3.3 {
+  list [file exists test.db-shm] [file exists test.db-wal]
+} {0 1}
+
+# EVIDENCE-OF: R-31969-57825 If EXCLUSIVE locking mode is set prior to
+# the first WAL-mode database access, then SQLite never attempts to call
+# any of the shared-memory methods and hence no shared-memory wal-index
+# is ever created.
+#
+db close
+sqlite3 db test.db
+do_execsql_test 2.1.1 {
+  PRAGMA locking_mode = EXCLUSIVE;
+  SELECT * FROM t1;
+} {exclusive 1 2 3 4}
+do_test 2.1.2 {
+  list [file exists test.db-shm] [file exists test.db-wal]
+} {0 1}
+
+# EVIDENCE-OF: R-36328-16367 In that case, the database connection
+# remains in EXCLUSIVE mode as long as the journal mode is WAL; attempts
+# to change the locking mode using "PRAGMA locking_mode=NORMAL;" are
+# no-ops.
+#
+do_execsql_test 2.2.1 {
+  PRAGMA locking_mode = NORMAL;
+  SELECT * FROM t1;
+} {exclusive 1 2 3 4}
+do_test 2.2.2 {
+  sqlite3 db2 test.db
+  catchsql {SELECT * FROM t1} db2
+} {1 {database is locked}}
+db2 close
+
+# EVIDENCE-OF: R-63522-46088 The only way to change out of EXCLUSIVE
+# locking mode is to first change out of WAL journal mode.
+#
+do_execsql_test 2.3.1 {
+  PRAGMA journal_mode = DELETE;
+  SELECT * FROM t1;
+} {delete 1 2 3 4}
+do_test 2.3.2 {
+  sqlite3 db2 test.db
+  catchsql {SELECT * FROM t1} db2
+} {1 {database is locked}}
+do_execsql_test 2.3.3 {
+  PRAGMA locking_mode = NORMAL;
+  SELECT * FROM t1;
+} {normal 1 2 3 4}
+do_test 2.3.4 {
+  sqlite3 db2 test.db
+  catchsql {SELECT * FROM t1} db2
+} {0 {1 2 3 4}}
+db2 close
+db close
+
+
+# EVIDENCE-OF: R-57239-11845 If NORMAL locking mode is in effect for the
+# first WAL-mode database access, then the shared-memory wal-index is
+# created.
+#
+do_test 3.0 {
+  sqlite3 db test.db
+  execsql { PRAGMA journal_mode = WAL }
+  db close
+} {}
+do_test 3.1 {
+  sqlite3 db test.db
+  execsql { SELECT * FROM t1 }
+  list [file exists test.db-shm] [file exists test.db-wal]
+} {1 1}
+
+# EVIDENCE-OF: R-13779-07711 As long as exactly one connection is using
+# a shared-memory wal-index, the locking mode can be changed freely
+# between NORMAL and EXCLUSIVE.
+#
+do_execsql_test 3.2.1 {
+  PRAGMA locking_mode = EXCLUSIVE;
+  PRAGMA locking_mode = NORMAL;
+  PRAGMA locking_mode = EXCLUSIVE;
+  INSERT INTO t1 VALUES(5, 6);
+} {exclusive normal exclusive}
+do_test 3.2.2 {
+  sqlite3 db2 test.db
+  catchsql { SELECT * FROM t1 } db2
+} {1 {database is locked}}
+
+# EVIDENCE-OF: R-10993-11647 It is only when the shared-memory wal-index
+# is omitted, when the locking mode is EXCLUSIVE prior to the first
+# WAL-mode database access, that the locking mode is stuck in EXCLUSIVE.
+#
+do_execsql_test 3.2.3 {
+  PRAGMA locking_mode = NORMAL;
+  SELECT * FROM t1;
+} {normal 1 2 3 4 5 6}
+do_test 3.2.4 {
+  catchsql { SELECT * FROM t1 } db2
+} {0 {1 2 3 4 5 6}}
+
+do_catchsql_test 3.2.5 {
+  PRAGMA locking_mode = EXCLUSIVE;
+  INSERT INTO t1 VALUES(7, 8);
+} {1 {database is locked}}
+
+db2 close
+
+# EVIDENCE-OF: R-46197-42811 This means that the underlying VFS must
+# support the "version 2" shared-memory.
+#
+# EVIDENCE-OF: R-55316-21772 If the VFS does not support shared-memory
+# methods, then the attempt to open a database that is already in WAL
+# mode, or the attempt convert a database into WAL mode, will fail.
+#
+db close
+do_test 3.4.1 {
+  sqlite3 db test.db -vfs oldvfs
+  catchsql { SELECT * FROM t1 }
+} {1 {unable to open database file}}
+db close
+do_test 3.4.2 {
+  forcedelete test.db2
+  sqlite3 db test.db2 -vfs oldvfs
+  catchsql { PRAGMA journal_mode = WAL }
+} {0 delete}
+db close
+
+
+# EVIDENCE-OF: R-22428-28959 To prevent older versions of SQLite from
+# trying to recover a WAL-mode database (and making matters worse) the
+# database file format version numbers (bytes 18 and 19 in the database
+# header) are increased from 1 to 2 in WAL mode.
+#
+reset_db
+do_execsql_test 4.1.1 { CREATE TABLE t1(x, y) }
+do_test 4.1.2 { hexio_read test.db 18 2 } {0101}
+do_execsql_test 4.1.3 { PRAGMA journal_mode = wAL } {wal}
+do_test 4.1.4 { hexio_read test.db 18 2 } {0202}
+
+
+# EVIDENCE-OF: R-02535-05811 One can explicitly change out of WAL mode
+# using a pragma such as this: PRAGMA journal_mode=DELETE;
+#
+do_execsql_test 4.2.1 { INSERT INTO t1 VALUES(1, 1); } {}
+do_test 4.2.2 { file exists test.db-wal } {1}
+do_execsql_test 4.2.3 { PRAGMA journal_mode = delete } {delete}
+do_test 4.2.4 { file exists test.db-wal } {0}
+
+# EVIDENCE-OF: R-60175-02388 Deliberately changing out of WAL mode
+# changes the database file format version numbers back to 1 so that
+# older versions of SQLite can once again access the database file.
+#
+do_test 4.3 { hexio_read test.db 18 2 } {0101}
+
+finish_test