Defer schema resets when the query planner is running.

Proposed fix for ticket [be436a7f4587ce517].

FossilOrigin-Name: a7bc7752ba0266684f5317e424a4ee9add4af002272082183519e708ab9ffc79

manifest

@@ -1,5 +1,5 @@
-C Avoid\sa\stest\sfor\sCURTYPE_BTREE\sin\ssqlite3VdbeCursorMoveto()\sin\sorder\sto\sreduce\nthe\ssize\sand\simprove\sthe\sperformance\sof\sOP_Column.
-D 2017-08-16T19:20:20.392
+C Defer\sschema\sresets\swhen\sthe\squery\splanner\sis\srunning.\nProposed\sfix\sfor\sticket\s[be436a7f4587ce517].
+D 2017-08-17T02:26:35.841
 F Makefile.in d9873c9925917cca9990ee24be17eb9613a668012c85a343aef7e5536ae266e8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 02b469e9dcd5b7ee63fc1fb05babc174260ee4cfa4e0ef2e48c3c6801567a016
@@ -400,8 +400,8 @@ F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
 F src/btree.c e1a98bef27d6189df5c5b8b3c9b5e53d6b74bf9a936af97757c21e9ea6a5c6b2
 F src/btree.h 32ef5d3f25dc70ef1ee9cecf84a023c21378f06a57cd701d2e866e141b150f09
 F src/btreeInt.h 55b702efce17e5d1941865464227d3802cfc9c7c832fac81d4c94dced47a71fc
-F src/build.c f8a85d2ad14c2201e10c2fe7185e1cb3f1db8b0c90d40d1fb99c20b135ab71bc
-F src/callback.c 930648a084a3adc741c6471adfbdc50ba47ba3542421cb80a26f259f467de65e
+F src/build.c 559bce114d59bb6dd795a7985a9eaac781d374ff31422d134dc147f9667a4d21
+F src/callback.c 28a8ede982fde4129b828350f78f2c01fe7d12c74d1a0a05d7108ab36f308688
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c ff1be3eed7bdd75aaca61ca8dc848f7c9f850ef2fb9cb56f2734e922a098f9c0
 F src/date.c 48f743d88bbe88f848532d333cca84f26e52a4f217e86f86be7fc1b919c33d74
@@ -449,7 +449,7 @@ F src/pcache.h 521bb9610d38ef17a3cc9b5ddafd4546c2ea67fa3d0e464823d73c2a28d50e11
 F src/pcache1.c 0b793738b5dddaf0a645784835c6b5557b1ecfaee339af9c26810c6ecdb273aa
 F src/pragma.c cd6aeda3587be6c5c08f9b2d45eae6068666a03c9d077c8c43cdb85fb0aa70f2
 F src/pragma.h bb83728944b42f6d409c77f5838a8edbdb0fe83046c5496ffc9602b40340a324
-F src/prepare.c 3cbb99757d7295997674972f9dd2331c5c544368854ca08954c9beb1e9b6145a
+F src/prepare.c 5da8a0563eff02e23584ec32863273eb3b1ac30bc736e1084efbcbf7379d1a56
 F src/printf.c 439c145d71ff9e0328ec26b7db23a45f995f742d3207dd546e034cdc1667ac9c
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 4324a94573b1e29286f8121e4881db59eaedc014afeb274c8d3e07ed282e0e20
@@ -460,7 +460,7 @@ F src/shell.c.in b5725acacba95ccefa57b6d068f710e29ba8239c3aa704628a1902a1f729c17
 F src/sqlite.h.in f0bd1abf5e27bd22b3bcaae2a861c1efc4ab7e752bf7eb102355135617eb8199
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a1fd3aa82f967da436164e0728a7d6841651fd0c6e27b9044e0eb9f6c8462e47
-F src/sqliteInt.h 854a122ff0ebde410a66d4f967e9923de9002f73965c6c9fa0db544bf7e657d1
+F src/sqliteInt.h 6dddca4e215f4088aeaf60aebaa6d913397d61422733e160f25ab9dc53605a36
 F src/sqliteLimit.h 1513bfb7b20378aa0041e7022d04acb73525de35b80b252f1b83fedb4de6a76b
 F src/status.c a9e66593dfb28a9e746cba7153f84d49c1ddc4b1
 F src/table.c b46ad567748f24a326d9de40e5b9659f96ffff34
@@ -1647,7 +1647,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 39543903282409ad3f139f8a0bb376661e7595a33af4f647945b1513a028ccb4
-R 6446f3c323d2c08f3899473bfc8c1574
+P f078deb25149b7b1881b7f3374b343d0677e82336d8fdd7f1cdd06d926b5dd57
+R 1aca6a5cd400a792803d04295cde6ca8
 U drh
-Z 68326b6d5ed2188a1ee820e19559d5ac
+Z ee696b9e27abcfab805d4537aa8e005a

manifest.uuid

@@ -1 +1 @@
-f078deb25149b7b1881b7f3374b343d0677e82336d8fdd7f1cdd06d926b5dd57
+a7bc7752ba0266684f5317e424a4ee9add4af002272082183519e708ab9ffc79

src/build.c

@@ -514,28 +514,26 @@ void sqlite3CollapseDatabaseArray(sqlite3 *db){
 
 /*
 ** Reset the schema for the database at index iDb.  Also reset the
-** TEMP schema.
+** TEMP schema.  The reset is deferred if db->nSchemaLock is not zero.
+** Deferred resets may be run by calling with iDb<0.
 */
 void sqlite3ResetOneSchema(sqlite3 *db, int iDb){
-  Db *pDb;
+  int i;
   assert( iDb<db->nDb );
 
-  /* Case 1:  Reset the single schema identified by iDb */
-  pDb = &db->aDb[iDb];
-  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
-  assert( pDb->pSchema!=0 );
-  sqlite3SchemaClear(pDb->pSchema);
-
-  /* If any database other than TEMP is reset, then also reset TEMP
-  ** since TEMP might be holding triggers that reference tables in the
-  ** other database.
-  */
-  if( iDb!=1 ){
-    pDb = &db->aDb[1];
-    assert( pDb->pSchema!=0 );
-    sqlite3SchemaClear(pDb->pSchema);
+  if( iDb>=0 ){
+    assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
+    DbSetProperty(db, iDb, DB_ResetWanted);
+    DbSetProperty(db, 1, DB_ResetWanted);
+  }
+
+  if( db->nSchemaLock==0 ){
+    for(i=0; i<db->nDb; i++){
+      if( DbHasProperty(db, i, DB_ResetWanted) ){
+        sqlite3SchemaClear(db->aDb[i].pSchema);
+      }
+    }
   }
-  return;
 }
 
 /*
@@ -545,6 +543,7 @@ void sqlite3ResetOneSchema(sqlite3 *db, int iDb){
 void sqlite3ResetAllSchemasOfConnection(sqlite3 *db){
   int i;
   sqlite3BtreeEnterAll(db);
+  assert( db->nSchemaLock==0 );
   for(i=0; i<db->nDb; i++){
     Db *pDb = &db->aDb[i];
     if( pDb->pSchema ){
@@ -2155,6 +2154,9 @@ int sqlite3ViewGetColumnNames(Parse *pParse, Table *pTable){
   int nErr = 0;     /* Number of errors encountered */
   int n;            /* Temporarily holds the number of cursors assigned */
   sqlite3 *db = pParse->db;  /* Database connection for malloc errors */
+#ifndef SQLITE_OMIT_VIRTUALTABLE	
+  int rc;
+#endif
 #ifndef SQLITE_OMIT_AUTHORIZATION
   sqlite3_xauth xAuth;       /* Saved xAuth pointer */
 #endif
@@ -2162,7 +2164,10 @@ int sqlite3ViewGetColumnNames(Parse *pParse, Table *pTable){
   assert( pTable );
 
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  if( sqlite3VtabCallConnect(pParse, pTable) ){
+  db->nSchemaLock++;
+  rc = sqlite3VtabCallConnect(pParse, pTable);
+  db->nSchemaLock--;
+  if( rc ){
     return SQLITE_ERROR;
   }
   if( IsVirtual(pTable) ) return 0;

src/callback.c

@@ -457,8 +457,8 @@ void sqlite3SchemaClear(void *p){
   pSchema->pSeqTab = 0;
   if( pSchema->schemaFlags & DB_SchemaLoaded ){
     pSchema->iGeneration++;
-    pSchema->schemaFlags &= ~DB_SchemaLoaded;
   }
+  pSchema->schemaFlags &= ~(DB_SchemaLoaded|DB_ResetWanted);
 }
 
 /*

src/prepare.c

@@ -686,7 +686,8 @@ static int sqlite3LockAndPrepare(
   sqlite3_mutex_enter(db->mutex);
   sqlite3BtreeEnterAll(db);
   rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
-  if( rc==SQLITE_SCHEMA ){
+  if( rc==SQLITE_SCHEMA && db->nSchemaLock==0 ){
+    sqlite3ResetOneSchema(db, -1);
     sqlite3_finalize(*ppStmt);
     rc = sqlite3Prepare(db, zSql, nBytes, prepFlags, pOld, ppStmt, pzTail);
   }

src/sqliteInt.h

@@ -1213,6 +1213,7 @@ struct Schema {
 #define DB_SchemaLoaded    0x0001  /* The schema has been loaded */
 #define DB_UnresetViews    0x0002  /* Some views have defined column names */
 #define DB_Empty           0x0004  /* The file is empty (length 0 bytes) */
+#define DB_ResetWanted     0x0008  /* Reset the schema when nSchemaLock==0 */
 
 /*
 ** The number of different kinds of things that can be limited
@@ -1329,6 +1330,7 @@ struct sqlite3 {
   u32 flags;                    /* flags settable by pragmas. See below */
   i64 lastRowid;                /* ROWID of most recent insert (see above) */
   i64 szMmap;                   /* Default mmap_size setting */
+  u32 nSchemaLock;              /* Do not reset the schema when non-zero */
   unsigned int openFlags;       /* Flags passed to sqlite3_vfs.xOpen() */
   int errCode;                  /* Most recent error code (SQLITE_*) */
   int errMask;                  /* & result codes with this before returning */