Prototype implementation of IF EXISTS and IF NOT EXISTS clauses on the

various forms of ALTER TALE.

FossilOrigin-Name: 460abf93ac6c47b0e3462e941d5de8e6b678dce9fac04a1e4923e2bf65cb59b2

manifest

@@ -1,5 +1,5 @@
-C Writes\sto\sthe\ssubjournal\sshould\sbe\sall-or-nothing.\s\sFix\sfor\ndbsqlfuzz\sfe3c397fb90029313446c4e0f4a6cd0c81dd9621.
-D 2022-02-08T15:14:18.391
+C Prototype\simplementation\sof\sIF\sEXISTS\sand\sIF\sNOT\sEXISTS\sclauses\son\sthe\nvarious\sforms\sof\sALTER\sTALE.
+D 2022-02-09T16:18:44.549
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -485,7 +485,7 @@ F spec.template 86a4a43b99ebb3e75e6b9a735d5fd293a24e90ca
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
-F src/alter.c e31cae888bc3077e34f9a82c6b4a96e4e44d37861eeb6472d68a378f1e8e46ba
+F src/alter.c 60dd7d624985ea5502aaec0852b6a516622437369d2138b1d4038a96400a95f8
 F src/analyze.c 7518b99e07c5494111fe3bd867f28f804b6c5c1ad0703ec3d116de9bab3fa516
 F src/attach.c f26d400f3ffe2cdca01406bca70e5f58c5488bf165b4fc37c228136dfcf1b583
 F src/auth.c f4fa91b6a90bbc8e0d0f738aa284551739c9543a367071f55574681e0f24f8cf
@@ -495,7 +495,7 @@ F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
 F src/btree.c ddab31c38d5f16114bc68392430556b1063fe14e0020f9a56d2c35ddd58ba7e3
 F src/btree.h 74d64b8f28cfa4a894d14d4ed64fa432cd697b98b61708d4351482ae15913e22
 F src/btreeInt.h ee9348c4cb9077243b049edc93a82c1f32ca48baeabf2140d41362b9f9139ff7
-F src/build.c b59ff41525c10b429adc277d3bca6e433b09d055b0df8c1529385763cea8bb04
+F src/build.c b6ab5a41941e0b1fd4caf644f52c0fff650504d0def5d6036d9696875319d4b4
 F src/callback.c 4c19af69835787bfe790ac560f3071a824eb629f34e41f97b52ce5235c77de1c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 2cce39df1a13e05b7633e6d21b651f21492471f991dd7b323a4ee4e7b7f0b7f1
@@ -541,7 +541,7 @@ F src/os_win.c 77d39873836f1831a9b0b91894fec45ab0e9ca8e067dc8c549e1d1eca1566fe9
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 29e4d6d8e0a6d092644c58109a36293d1ea6fd2e1e7a26042f5462fd819493b7
 F src/pager.h 4bf9b3213a4b2bebbced5eaa8b219cf25d4a82f385d093cd64b7e93e5285f66f
-F src/parse.y b34d4eb8105271ea0d577ef165bb7b2a2b70e03b2e694e68e2e43b76389bf660
+F src/parse.y 0ab7c540d99bc0860d6ef07991ff9cc78673e4f4a80f431320f8155c769bf96e
 F src/pcache.c 084e638432c610f95aea72b8509f0845d2791293f39d1b82f0c0a7e089c3bb6b
 F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
 F src/pcache1.c 54881292a9a5db202b2c0ac541c5e3ef9a5e8c4f1c1383adb2601d5499a60e65
@@ -557,7 +557,7 @@ F src/shell.c.in b800bf8e02d9b4fd97078b68ca4371048f7196fc63accaa99c3c5943f72c80a
 F src/sqlite.h.in b07c70b7f3b9363aeb59ead2c2ceb2748b890c0012eb8a399987331baae09d1c
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a95cb9ed106e3d39e2118e4dcc15a14faec3fa50d0093425083d340d9dfd96e6
-F src/sqliteInt.h b6619030ed13b2a8d49c0b5cb0525db1f727966b65ab1ec40b5f11102af7254d
+F src/sqliteInt.h 5a22bd250cb65077b66cad652f6a3257547a0952f391e9f29574c4757d5b6629
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 4b8bc2a6905163a38b739854a35b826c737333fab5b1f8e03fa7eb9a4799c4c1
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -1943,8 +1943,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 1269206db810460e55a52e178ba3332add42a11f66c5f292f8f0d29ccd61a4b8
-R 152bd288ae589530fc2745d322f45fd2
+P 22cc55e84f67f6f39b7dba07a4ef7ae958b2d926633faec91a278922053e50c6
+R 625d7798cb6317c1febdd91af24cd0e1
+T *branch * alter-table-if-exists
+T *sym-alter-table-if-exists *
+T -sym-trunk *
 U drh
-Z b4c4dbfb44e2c416fb7b7bc180b39619
+Z 4d9daece2ae14d7891d26fed97e3045c
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-22cc55e84f67f6f39b7dba07a4ef7ae958b2d926633faec91a278922053e50c6
+460abf93ac6c47b0e3462e941d5de8e6b678dce9fac04a1e4923e2bf65cb59b2

src/alter.c

@@ -124,7 +124,8 @@ static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
 void sqlite3AlterRenameTable(
   Parse *pParse,            /* Parser context. */
   SrcList *pSrc,            /* The table to rename. */
-  Token *pName              /* The new table name. */
+  Token *pName,             /* The new table name. */
+  int noErr                 /* Suppress "no such table" errors */
 ){
   int iDb;                  /* Database that contains the table */
   char *zDb;                /* Name of database iDb */
@@ -140,8 +141,16 @@ void sqlite3AlterRenameTable(
   assert( pSrc->nSrc==1 );
   assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );
 
+  if( noErr ) db->suppressErr++;
   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
-  if( !pTab ) goto exit_rename_table;
+  if( noErr ) db->suppressErr--;
+  if( !pTab ){
+    if( noErr ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    goto exit_rename_table;
+  }
   iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
   zDb = db->aDb[iDb].zDbSName;
 
@@ -328,7 +337,7 @@ void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
   if( pParse->nErr ) return;
   assert( db->mallocFailed==0 );
   pNew = pParse->pNewTable;
-  assert( pNew );
+  if( pNew==0 ) return;  /* ALTER TABLE IF EXISTS and it does not exist */
 
   assert( sqlite3BtreeHoldsAllMutexes(db) );
   iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
@@ -338,6 +347,12 @@ void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
   pDflt = sqlite3ColumnExpr(pNew, pCol);
   pTab = sqlite3FindTable(db, zTab, zDb);
   assert( pTab );
+  if( pParse->ifNotExists>=2 ){
+    sqlite3CodeVerifyNamedSchema(pParse, zDb);
+    sqlite3ForceNotReadOnly(pParse);
+    return;
+  }
+
 
 #ifndef SQLITE_OMIT_AUTHORIZATION
   /* Invoke the authorization callback. */
@@ -475,7 +490,12 @@ void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
 ** Routine sqlite3AlterFinishAddColumn() will be called to complete
 ** coding the "ALTER TABLE ... ADD" statement.
 */
-void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
+void sqlite3AlterBeginAddColumn(
+  Parse *pParse,
+  SrcList *pSrc,
+  int ifExists,          /* ALTER TABLE IF EXISTS... */
+  int ifNotExists        /* ... ADD COLUMN IF NOT EXISTS .... */
+){
   Table *pNew;
   Table *pTab;
   int iDb;
@@ -485,10 +505,21 @@ void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
 
   /* Look up the table being altered. */
   assert( pParse->pNewTable==0 );
+  assert( ifExists==0 || ifExists==1 );
+  assert( ifNotExists==0 || ifNotExists==1 );
   assert( sqlite3BtreeHoldsAllMutexes(db) );
   if( db->mallocFailed ) goto exit_begin_add_column;
+  db->suppressErr += ifExists;
   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
-  if( !pTab ) goto exit_begin_add_column;
+  db->suppressErr -= ifExists;
+  if( !pTab ){
+    if( ifExists ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    goto exit_begin_add_column;
+  }
+  pParse->ifNotExists = ifNotExists;
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
   if( IsVirtual(pTab) ){
@@ -592,7 +623,9 @@ void sqlite3AlterRenameColumn(
   Parse *pParse,                  /* Parsing context */
   SrcList *pSrc,                  /* Table being altered.  pSrc->nSrc==1 */
   Token *pOld,                    /* Name of column being changed */
-  Token *pNew                     /* New column name */
+  Token *pNew,                    /* New column name */
+  int ifExistsTable,              /* IF EXISTS on table */
+  int ifExistsCol                 /* IF EXISTS on the column */
 ){
   sqlite3 *db = pParse->db;       /* Database connection */
   Table *pTab;                    /* Table being updated */
@@ -604,8 +637,16 @@ void sqlite3AlterRenameColumn(
   int bQuote;                     /* True to quote the new name */
 
   /* Locate the table to be altered */
+  db->suppressErr += ifExistsTable;
   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
-  if( !pTab ) goto exit_rename_column;
+  db->suppressErr -= ifExistsTable;
+  if( !pTab ){
+    if( ifExistsTable ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    goto exit_rename_column;
+  }
 
   /* Cannot alter a system table */
   if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_rename_column;
@@ -631,7 +672,12 @@ void sqlite3AlterRenameColumn(
     if( 0==sqlite3StrICmp(pTab->aCol[iCol].zCnName, zOld) ) break;
   }
   if( iCol==pTab->nCol ){
-    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pOld);
+    if( ifExistsCol ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }else{
+      sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pOld);
+    }
     goto exit_rename_column;
   }
 
@@ -2103,7 +2149,13 @@ drop_column_done:
 ** statement. Argument pSrc contains the possibly qualified name of the
 ** table being edited, and token pName the name of the column to drop.
 */
-void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, const Token *pName){
+void sqlite3AlterDropColumn(
+  Parse *pParse,                  /* Parsing context */
+  SrcList *pSrc,                  /* Table to be altered */
+  const Token *pName,             /* Name of column to be dropped */
+  int ifExistsTable,              /* IF EXISTS flag on the table */
+  int ifExistsColumn              /* IF EXISTS flags on the column */
+){
   sqlite3 *db = pParse->db;       /* Database handle */
   Table *pTab;                    /* Table to modify */
   int iDb;                        /* Index of db containing pTab in aDb[] */
@@ -2115,8 +2167,16 @@ void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, const Token *pName){
   assert( pParse->pNewTable==0 );
   assert( sqlite3BtreeHoldsAllMutexes(db) );
   if( NEVER(db->mallocFailed) ) goto exit_drop_column;
+  db->suppressErr += ifExistsTable;
   pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
-  if( !pTab ) goto exit_drop_column;
+  db->suppressErr -= ifExistsTable;
+  if( !pTab ){
+    if( ifExistsTable ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }
+    goto exit_drop_column;
+  }
 
   /* Make sure this is not an attempt to ALTER a view, virtual table or 
   ** system table. */
@@ -2131,7 +2191,12 @@ void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, const Token *pName){
   }
   iCol = sqlite3ColumnIndex(pTab, zCol);
   if( iCol<0 ){
-    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pName);
+    if( ifExistsColumn ){
+      sqlite3CodeVerifyNamedSchema(pParse, pSrc->a[0].zDatabase);
+      sqlite3ForceNotReadOnly(pParse);
+    }else{
+      sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pName);
+    }
     goto exit_drop_column;
   }
 

src/build.c

@@ -1189,7 +1189,7 @@ i16 sqlite3TableColumnToStorage(Table *pTab, i16 iCol){
 ** will return false for sqlite3_stmt_readonly() even if that statement
 ** is a read-only no-op.
 */
-static void sqlite3ForceNotReadOnly(Parse *pParse){
+void sqlite3ForceNotReadOnly(Parse *pParse){
   int iReg = ++pParse->nMem;
   Vdbe *v = sqlite3GetVdbe(pParse);
   if( v ){
@@ -1561,7 +1561,11 @@ void sqlite3AddColumn(Parse *pParse, Token sName, Token sType){
   hName = sqlite3StrIHash(z);
   for(i=0; i<p->nCol; i++){
     if( p->aCol[i].hName==hName && sqlite3StrICmp(z, p->aCol[i].zCnName)==0 ){
-      sqlite3ErrorMsg(pParse, "duplicate column name: %s", z);
+      if( pParse->ifNotExists ){
+        pParse->ifNotExists = 2;
+      }else{
+        sqlite3ErrorMsg(pParse, "duplicate column name: %s", z);
+      }
       sqlite3DbFree(db, z);
       return;
     }

src/parse.y

@@ -1637,24 +1637,24 @@ cmd ::= ANALYZE nm(X) dbnm(Y).  {sqlite3Analyze(pParse, &X, &Y);}
 //////////////////////// ALTER TABLE table ... ////////////////////////////////
 %ifndef SQLITE_OMIT_ALTERTABLE 
 %ifndef SQLITE_OMIT_VIRTUALTABLE
-cmd ::= ALTER TABLE fullname(X) RENAME TO nm(Z). {
-  sqlite3AlterRenameTable(pParse,X,&Z);
+cmd ::= ALTER TABLE ifexists(E) fullname(X) RENAME TO nm(Z). {
+  sqlite3AlterRenameTable(pParse,X,&Z,E);
 }
-cmd ::= ALTER TABLE add_column_fullname
-        ADD kwcolumn_opt columnname(Y) carglist. {
+cmd ::= ALTER TABLE add_column_fullname columnname(Y) carglist. {
   Y.n = (int)(pParse->sLastToken.z-Y.z) + pParse->sLastToken.n;
   sqlite3AlterFinishAddColumn(pParse, &Y);
 }
-cmd ::= ALTER TABLE fullname(X) DROP kwcolumn_opt nm(Y). {
-  sqlite3AlterDropColumn(pParse, X, &Y);
+cmd ::= ALTER TABLE ifexists(E1) fullname(X) DROP kwcolumn_opt ifexists(E2) nm(Y). {
+  sqlite3AlterDropColumn(pParse, X, &Y, E1, E2);
 }
 
-add_column_fullname ::= fullname(X). {
+add_column_fullname ::= ifexists(E1) fullname(X) ADD kwcolumn_opt ifnotexists(E2). {
   disableLookaside(pParse);
-  sqlite3AlterBeginAddColumn(pParse, X);
+  sqlite3AlterBeginAddColumn(pParse, X, E1, E2);
 }
-cmd ::= ALTER TABLE fullname(X) RENAME kwcolumn_opt nm(Y) TO nm(Z). {
-  sqlite3AlterRenameColumn(pParse, X, &Y, &Z);
+cmd ::= ALTER TABLE ifexists(E1) fullname(X)
+        RENAME kwcolumn_opt ifexists(E2) nm(Y) TO nm(Z). {
+  sqlite3AlterRenameColumn(pParse, X, &Y, &Z, E1, E2);
 }
 
 kwcolumn_opt ::= .

src/sqliteInt.h

@@ -3580,6 +3580,7 @@ struct Parse {
   u8 bReturning;       /* Coding a RETURNING trigger */
   u8 eOrconf;          /* Default ON CONFLICT policy for trigger steps */
   u8 disableTriggers;  /* True to disable triggers */
+  u8 ifNotExists;      /* IF NOT EXISTS flag on ALTER TABLE ADD COLUMN */
 
   /**************************************************************************
   ** Fields above must be initialized to zero.  The fields that follow,
@@ -4478,6 +4479,7 @@ i16 sqlite3TableColumnToIndex(Index*, i16);
   i16 sqlite3TableColumnToStorage(Table*, i16);
   i16 sqlite3StorageColumnToTable(Table*, i16);
 #endif
+void sqlite3ForceNotReadOnly(Parse*);
 void sqlite3StartTable(Parse*,Token*,Token*,int,int,int,int);
 #if SQLITE_ENABLE_HIDDEN_COLUMNS
   void sqlite3ColumnPropertiesFromName(Table*, Column*);
@@ -4917,8 +4919,8 @@ extern sqlite3_uint64 sqlite3NProfileCnt;
 void sqlite3RootPageMoved(sqlite3*, int, Pgno, Pgno);
 void sqlite3Reindex(Parse*, Token*, Token*);
 void sqlite3AlterFunctions(void);
-void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
-void sqlite3AlterRenameColumn(Parse*, SrcList*, Token*, Token*);
+void sqlite3AlterRenameTable(Parse*, SrcList*, Token*, int);
+void sqlite3AlterRenameColumn(Parse*, SrcList*, Token*, Token*,int,int);
 int sqlite3GetToken(const unsigned char *, int *);
 void sqlite3NestedParse(Parse*, const char*, ...);
 void sqlite3ExpirePreparedStatements(sqlite3*, int);
@@ -4942,8 +4944,8 @@ int sqlite3ResolveSelfReference(Parse*,Table*,int,Expr*,ExprList*);
 int sqlite3ResolveOrderGroupBy(Parse*, Select*, ExprList*, const char*);
 void sqlite3ColumnDefault(Vdbe *, Table *, int, int);
 void sqlite3AlterFinishAddColumn(Parse *, Token *);
-void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
-void sqlite3AlterDropColumn(Parse*, SrcList*, const Token*);
+void sqlite3AlterBeginAddColumn(Parse *, SrcList *,int,int);
+void sqlite3AlterDropColumn(Parse*, SrcList*, const Token*, int, int);
 const void *sqlite3RenameTokenMap(Parse*, const void*, const Token*);
 void sqlite3RenameTokenRemap(Parse*, const void *pTo, const void *pFrom);
 void sqlite3RenameExprUnmap(Parse*, Expr*);