diff --git a/manifest b/manifest
index 484e81c049..36e7f8c989 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Simplifications\sto\spager.c\sin\ssupport\sof\sstructural\scoverage\stesting.\s(CVS\s6927)
-D 2009-07-24T16:32:01
+C Allow\svirtual\stables\sto\sbe\sused\sin\sshared-cache\smode.\s(CVS\s6928)
+D 2009-07-24T17:58:53
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -99,21 +99,21 @@ F spec.template 86a4a43b99ebb3e75e6b9a735d5fd293a24e90ca
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 6be1ad09113570e1fc8dcaff84c9b0b337db5ffc
 F sqlite3.pc.in ae6f59a76e862f5c561eb32a380228a02afc3cad
-F src/alter.c 95f41d957f56407aac6224041ca5b954042318d1
+F src/alter.c 8b42cace4f8e312de596807ba2685179da64fec4
 F src/analyze.c e239496cfb5394ac8867f1c112905ddab8d01cd9
 F src/attach.c 13995348fc5a26cdd136a50806faf292aabc173f
 F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c cfbf6af5b0ababb4f06ed3e75c616dadaf47fcbd
 F src/btmutex.c 0f43a75bb5b8147b386e8e1c3e71ba734e3863b7
-F src/btree.c 64fbba1140bb06edbac2553cfd339145bbdc2665
+F src/btree.c c1d3d67007f2f49697b4204bf44f2a8f45f750df
 F src/btree.h 577448a890c2ab9b21e6ab74f073526184bceebe
 F src/btreeInt.h 1c86297e69380f6577e7ae67452597dd8d5c2705
-F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
+F src/build.c a15de7c5d020a778b641fca0b2510126843f4b30
 F src/callback.c cb68b21b0d4ae7d11ae0e487933bce3323784dcf
 F src/complete.c 5ad5c6cd4548211867c204c41a126d73a9fbcea0
 F src/date.c ab5f7137656652a48434d64f96bdcdc823bb23b3
-F src/delete.c fb05e577ab273cc8a63b44809aa5078f72f475c1
+F src/delete.c 6f0192ecf2ae97dbbf4cccfa32639b504da70d4a
 F src/expr.c f6f21604c1367354b28d03c983a83279071a2948
 F src/fault.c dc88c821842157460750d2d61a8a8b4197d047ff
 F src/func.c 9856373f5315f6b8690d7f07f7191aa9f279ca87
@@ -121,7 +121,7 @@ F src/global.c 448419c44ce0701104c2121b0e06919b44514c0c
 F src/hash.c ebcaa921ffd9d86f7ea5ae16a0a29d1c871130a7
 F src/hash.h 35b216c13343d0b4f87d9f21969ac55ad72174e1
 F src/hwtime.h 4a1d45f4cae1f402ea19686acf24acf4f0cb53cb
-F src/insert.c 94e51344e01aea6be43e95cd24e8baa014d8c3d6
+F src/insert.c a4bbd811a15f8b24a311753da947d61368685db1
 F src/journal.c e00df0c0da8413ab6e1bb7d7cab5665d4a9000d0
 F src/legacy.c 54a11649f27ae55f4fcd6e6b5ba836f839cb8704
 F src/lempar.c 0c4d1ab0a5ef2b0381eb81a732c54f68f27a574d
@@ -154,16 +154,16 @@ F src/pcache.c 1dae135b70a029f81ed66f6e9b5d0db91480d5d0
 F src/pcache.h 9b927ccc5a538e31b4c3bc7eec4f976db42a1324
 F src/pcache1.c 6dc833c89feac405dd8b4858232c97e679f182ec
 F src/pragma.c 9eb44ac1d3dc1ac3ea4f444abe1a10ae8acaa16c
-F src/prepare.c 12e556fc9f72a6563db7099697f657d75d4bb91c
+F src/prepare.c 312ba96867ae9df6bd1a57cb84a9fd315e61cf8d
 F src/printf.c 508a1c59433353552b6553cba175eaa7331f8fc1
 F src/random.c 676b9d7ac820fe81e6fb2394ac8c10cff7f38628
 F src/resolve.c 4a61d03e49b15440878096e6030863fc628828f0
 F src/rowset.c c64dafba1f9fd876836c8db8682966b9d197eb1f
 F src/select.c 71748b8e244112cf73df9446c4246c192276c30d
 F src/shell.c db2643650b9268df89a4bedca3f1c6d9e786f1bb
-F src/sqlite.h.in 92a8960ca178cfbd73ce71cca65829c6262137ac
+F src/sqlite.h.in 5672d9a6e19f80c1c7f1276dbe10e7d51c8fd97b
 F src/sqlite3ext.h 1db7d63ab5de4b3e6b83dd03d1a4e64fef6d2a17
-F src/sqliteInt.h c638fff6a05bb1c546f361e8527385fef0638917
+F src/sqliteInt.h 11d239cc658823c719a3077ea2c7691795002c34
 F src/sqliteLimit.h ffe93f5a0c4e7bd13e70cd7bf84cfb5c3465f45d
 F src/status.c 237b193efae0cf6ac3f0817a208de6c6c6ef6d76
 F src/table.c cc86ad3d6ad54df7c63a3e807b5783c90411a08d
@@ -200,20 +200,20 @@ F src/test_thread.c b8a1ab7ca1a632f18e8a361880d5d65eeea08eac
 F src/test_wsd.c 3ae5101de6cbfda2720152ab659ea84079719241
 F src/tokenize.c af8a56e6a50c5042fc305bfa796275e9bf26ff2b
 F src/trigger.c c07c5157c58fcdb704f65d5f5e4775276e45bb8b
-F src/update.c a1bbe774bce495d62dce3df3f42a5f04c1de173a
+F src/update.c 7570d90842f0d9338906eeea443193358869ca97
 F src/utf.c 9541d28f40441812c0b40f00334372a0542c00ff
 F src/util.c 861d5b5c58be4921f0a254489ea94cb15f550ef8
 F src/vacuum.c 3fe0eebea6d2311c1c2ab2962887d11f7a4dcfb0
-F src/vdbe.c 3f4b02f59287cc65583c0bba371e9c7d047abad2
-F src/vdbe.h 35a648bc3279a120da24f34d9a25213ec15daf8a
+F src/vdbe.c 0ce57f8211899b59d1d6f1642f79e75fc212d6d0
+F src/vdbe.h 457b6c70f02885cec1f5225b5e6441d067b55d3f
 F src/vdbeInt.h 831c254a6eef237ef4664c8381a0137586567007
 F src/vdbeapi.c 0ab8ada7260b32031ca97f338caecf0812460624
-F src/vdbeaux.c a1ed07f91a9d59d39e97b2844554a07c91c9b809
+F src/vdbeaux.c e3943dae17dd29d749a3e9bb42e4eb7b7eca43ed
 F src/vdbeblob.c a3f3e0e877fc64ea50165eec2855f5ada4477611
 F src/vdbemem.c bfc25f9ef4fa914b473303566459552bdb2e008a
-F src/vtab.c 00902f289521041712fb0293d0bf8688c7af8e48
+F src/vtab.c b19c4e96dcf2b89b5b2ba48e8ef624e654a59b2c
 F src/walker.c 1edca756275f158b80f20eb6f104c8d3fcc96a04
-F src/where.c cf0d091748c2fa6f7df96e5b08d2db26fd2eb437
+F src/where.c bf56a85ab4f1e17f0c8060c97bd579cb8e0fa000
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/alias.test 4529fbc152f190268a15f9384a5651bbbabc9d87
 F test/all.test 14165b3e32715b700b5f0cbf8f6e3833dda0be45
@@ -703,7 +703,7 @@ F test/vtabC.test 1cf7896ab6859bfe3074244b2b0e12de5cbdd766
 F test/vtabD.test 74167b1578e5886fe4c886d6bef2fd1406444c42
 F test/vtab_alter.test 3a299749fee97ca3d53bd55717f536e4a2284856
 F test/vtab_err.test 0d4d8eb4def1d053ac7c5050df3024fd47a3fbd8
-F test/vtab_shared.test c19b2555b807ef2ee014c882cdda5bc8d84fcf48
+F test/vtab_shared.test 561305eff0bb574a983c29029ef294a4a895a14c
 F test/where.test de337a3fe0a459ec7c93db16a519657a90552330
 F test/where2.test 45eacc126aabb37959a387aa83e59ce1f1f03820
 F test/where3.test 97d3936e6a443b968f1a61cdcc0f673252000e94
@@ -741,7 +741,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P 2d2f42ca0a24ed8b33f9ad560c76a6c1301c757b
-R d83586425c23d3015fdf0b2326ebc67f
-U drh
-Z eeeb8d7f7200949823d967a49549fa65
+P 7222ad2667b95d6021d9ae47f548b76b224f46aa
+R 477ef377a502774f707ff161355dd337
+U danielk1977
+Z b547740a8551902f628dba2106d37250
diff --git a/manifest.uuid b/manifest.uuid
index 135cccaae8..d545e688d1 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-7222ad2667b95d6021d9ae47f548b76b224f46aa
\ No newline at end of file
+5d9e767a05e381235e064061043e30cc03a11a07
\ No newline at end of file
diff --git a/src/alter.c b/src/alter.c
index 36033a5095..be4a2e0862 100644
--- a/src/alter.c
+++ b/src/alter.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that used to generate VDBE code
 ** that implements the ALTER TABLE command.
 **
-** $Id: alter.c,v 1.61 2009/06/03 11:25:07 danielk1977 Exp $
+** $Id: alter.c,v 1.62 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -277,7 +277,7 @@ void sqlite3AlterRenameTable(
 #ifndef SQLITE_OMIT_TRIGGER
   char *zWhere = 0;         /* Where clause to locate temp triggers */
 #endif
-  int isVirtualRename = 0;  /* True if this is a v-table with an xRename() */
+  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */
   
   if( NEVER(db->mallocFailed) ) goto exit_rename_table;
   assert( pSrc->nSrc==1 );
@@ -332,8 +332,11 @@ void sqlite3AlterRenameTable(
   if( sqlite3ViewGetColumnNames(pParse, pTab) ){
     goto exit_rename_table;
   }
-  if( IsVirtual(pTab) && pTab->pMod->pModule->xRename ){
-    isVirtualRename = 1;
+  if( IsVirtual(pTab) ){
+    pVTab = sqlite3GetVTable(db, pTab);
+    if( pVTab->pVtab->pModule->xRename==0 ){
+      pVTab = 0;
+    }
   }
 #endif
 
@@ -346,7 +349,7 @@ void sqlite3AlterRenameTable(
   if( v==0 ){
     goto exit_rename_table;
   }
-  sqlite3BeginWriteOperation(pParse, isVirtualRename, iDb);
+  sqlite3BeginWriteOperation(pParse, pVTab!=0, iDb);
   sqlite3ChangeCookie(pParse, iDb);
 
   /* If this is a virtual table, invoke the xRename() function if
@@ -355,10 +358,10 @@ void sqlite3AlterRenameTable(
   ** SQLite tables) that are identified by the name of the virtual table.
   */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  if( isVirtualRename ){
+  if( pVTab ){
     int i = ++pParse->nMem;
     sqlite3VdbeAddOp4(v, OP_String8, 0, i, 0, zName, 0);
-    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pTab->pVtab, P4_VTAB);
+    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
   }
 #endif
 
diff --git a/src/btree.c b/src/btree.c
index a855798784..0e902b8fe6 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.701 2009/07/23 01:44:00 drh Exp $
+** $Id: btree.c,v 1.702 2009/07/24 17:58:53 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -1700,7 +1700,6 @@ int sqlite3BtreeOpen(
       char *zFullPathname = sqlite3Malloc(nFullPathname);
       sqlite3_mutex *mutexShared;
       p->sharable = 1;
-      db->flags |= SQLITE_SharedCache;
       if( !zFullPathname ){
         sqlite3_free(p);
         return SQLITE_NOMEM;
diff --git a/src/build.c b/src/build.c
index 0696f1c82d..7136cbc1b3 100644
--- a/src/build.c
+++ b/src/build.c
@@ -22,7 +22,7 @@
 **     COMMIT
 **     ROLLBACK
 **
-** $Id: build.c,v 1.556 2009/07/01 16:12:08 danielk1977 Exp $
+** $Id: build.c,v 1.557 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -162,7 +162,7 @@ void sqlite3FinishCoding(Parse *pParse){
       {
         int i;
         for(i=0; i<pParse->nVtabLock; i++){
-          char *vtab = (char *)pParse->apVtabLock[i]->pVtab;
+          char *vtab = (char *)sqlite3GetVTable(db, pParse->apVtabLock[i]);
           sqlite3VdbeAddOp4(v, OP_VBegin, 0, 0, 0, vtab, P4_VTAB);
         }
         pParse->nVtabLock = 0;
@@ -424,6 +424,7 @@ void sqlite3ResetInternalSchema(sqlite3 *db, int iDb){
   }
   assert( iDb==0 );
   db->flags &= ~SQLITE_InternChanges;
+  sqlite3VtabUnlockList(db);
   sqlite3BtreeLeaveAll(db);
 
   /* If one or more of the auxiliary database files has been closed,
@@ -2002,7 +2003,7 @@ void sqlite3DropTable(Parse *pParse, SrcList *pName, int isView, int noErr){
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     }else if( IsVirtual(pTab) ){
       code = SQLITE_DROP_VTABLE;
-      zArg2 = pTab->pMod->zName;
+      zArg2 = sqlite3GetVTable(db, pTab)->pMod->zName;
 #endif
     }else{
       if( !OMIT_TEMPDB && iDb==1 ){
diff --git a/src/delete.c b/src/delete.c
index cbd8b375e7..a2c97bc15b 100644
--- a/src/delete.c
+++ b/src/delete.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** in order to generate code for DELETE FROM statements.
 **
-** $Id: delete.c,v 1.204 2009/06/23 20:28:54 drh Exp $
+** $Id: delete.c,v 1.205 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -43,16 +43,26 @@ Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
 ** writable return 0;
 */
 int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
-  if( ((pTab->tabFlags & TF_Readonly)!=0
-        && (pParse->db->flags & SQLITE_WriteSchema)==0
-        && pParse->nested==0) 
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-      || (pTab->pMod && pTab->pMod->pModule->xUpdate==0)
-#endif
+  /* A table is not writable under the following circumstances:
+  **
+  **   1) It is a virtual table and no implementation of the xUpdate method
+  **      has been provided, or
+  **   2) It is a system table (i.e. sqlite_master), this call is not
+  **      part of a nested parse and writable_schema pragma has not 
+  **      been specified.
+  **
+  ** In either case leave an error message in pParse and return non-zero.
+  */
+  if( ( IsVirtual(pTab) 
+     && sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )
+   || ( (pTab->tabFlags & TF_Readonly)!=0
+     && (pParse->db->flags & SQLITE_WriteSchema)==0
+     && pParse->nested==0 )
   ){
     sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
     return 1;
   }
+
 #ifndef SQLITE_OMIT_VIEW
   if( !viewOk && pTab->pSelect ){
     sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
@@ -264,6 +274,12 @@ void sqlite3DeleteFrom(
 # define isView 0
 #endif
 
+  /* If pTab is really a view, make sure it has been initialized.
+  */
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+    goto delete_from_cleanup;
+  }
+
   if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
     goto delete_from_cleanup;
   }
@@ -277,12 +293,6 @@ void sqlite3DeleteFrom(
   }
   assert(!isView || pTrigger);
 
-  /* If pTab is really a view, make sure it has been initialized.
-  */
-  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
-    goto delete_from_cleanup;
-  }
-
   /* Allocate a cursor used to store the old.* data for a trigger.
   */
   if( pTrigger ){ 
@@ -443,9 +453,9 @@ void sqlite3DeleteFrom(
       /* Delete the row */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
       if( IsVirtual(pTab) ){
-        const char *pVtab = (const char *)pTab->pVtab;
+        const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
         sqlite3VtabMakeWritable(pParse, pTab);
-        sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVtab, P4_VTAB);
+        sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVTab, P4_VTAB);
       }else
 #endif
       {
diff --git a/src/insert.c b/src/insert.c
index f6d8b1c390..43fbe58515 100644
--- a/src/insert.c
+++ b/src/insert.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle INSERT statements in SQLite.
 **
-** $Id: insert.c,v 1.269 2009/06/23 20:28:54 drh Exp $
+** $Id: insert.c,v 1.270 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -131,9 +131,14 @@ void sqlite3TableAffinityStr(Vdbe *v, Table *pTab){
 ** a statement of the form  "INSERT INTO <iDb, pTab> SELECT ..." can 
 ** run without using temporary table for the results of the SELECT. 
 */
-static int readsTable(Vdbe *v, int iStartAddr, int iDb, Table *pTab){
+static int readsTable(Parse *p, int iStartAddr, int iDb, Table *pTab){
+  Vdbe *v = sqlite3GetVdbe(p);
   int i;
   int iEnd = sqlite3VdbeCurrentAddr(v);
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  VTable *pVTab = IsVirtual(pTab) ? sqlite3GetVTable(p->db, pTab) : 0;
+#endif
+
   for(i=iStartAddr; i<iEnd; i++){
     VdbeOp *pOp = sqlite3VdbeGetOp(v, i);
     assert( pOp!=0 );
@@ -150,7 +155,7 @@ static int readsTable(Vdbe *v, int iStartAddr, int iDb, Table *pTab){
       }
     }
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-    if( pOp->opcode==OP_VOpen && pOp->p4.pVtab==pTab->pVtab ){
+    if( pOp->opcode==OP_VOpen && pOp->p4.pVtab==pVTab ){
       assert( pOp->p4.pVtab!=0 );
       assert( pOp->p4type==P4_VTAB );
       return 1;
@@ -504,15 +509,6 @@ void sqlite3Insert(
 #endif
   assert( (pTrigger && tmask) || (pTrigger==0 && tmask==0) );
 
-  /* Ensure that:
-  *  (a) the table is not read-only, 
-  *  (b) that if it is a view then ON INSERT triggers exist
-  */
-  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
-    goto insert_cleanup;
-  }
-  assert( pTab!=0 );
-
   /* If pTab is really a view, make sure it has been initialized.
   ** ViewGetColumnNames() is a no-op if pTab is not a view (or virtual 
   ** module table).
@@ -521,6 +517,14 @@ void sqlite3Insert(
     goto insert_cleanup;
   }
 
+  /* Ensure that:
+  *  (a) the table is not read-only, 
+  *  (b) that if it is a view then ON INSERT triggers exist
+  */
+  if( sqlite3IsReadOnly(pParse, pTab, tmask) ){
+    goto insert_cleanup;
+  }
+
   /* Allocate a VDBE
   */
   v = sqlite3GetVdbe(pParse);
@@ -620,7 +624,7 @@ void sqlite3Insert(
     ** of the tables being read by the SELECT statement.  Also use a 
     ** temp table in the case of row triggers.
     */
-    if( pTrigger || readsTable(v, addrSelect, iDb, pTab) ){
+    if( pTrigger || readsTable(pParse, addrSelect, iDb, pTab) ){
       useTempTable = 1;
     }
 
@@ -976,9 +980,9 @@ void sqlite3Insert(
     */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( IsVirtual(pTab) ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
       sqlite3VtabMakeWritable(pParse, pTab);
-      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns,
-                     (const char*)pTab->pVtab, P4_VTAB);
+      sqlite3VdbeAddOp4(v, OP_VUpdate, 1, pTab->nCol+2, regIns, pVTab, P4_VTAB);
     }else
 #endif
     {
diff --git a/src/prepare.c b/src/prepare.c
index 4edbee0ac6..55208ea1b9 100644
--- a/src/prepare.c
+++ b/src/prepare.c
@@ -13,7 +13,7 @@
 ** interface, and routines that contribute to loading the database schema
 ** from disk.
 **
-** $Id: prepare.c,v 1.128 2009/07/03 19:19:50 drh Exp $
+** $Id: prepare.c,v 1.129 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -581,6 +581,7 @@ static int sqlite3Prepare(
     }
   }
 
+  sqlite3VtabUnlockList(db);
 
   pParse->db = db;
   if( nBytes>=0 && (nBytes==0 || zSql[nBytes-1]!=0) ){
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 29c14c7a2a..e62b4d5fb6 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -30,7 +30,7 @@
 ** the version number) and changes its name to "sqlite3.h" as
 ** part of the build process.
 **
-** @(#) $Id: sqlite.h.in,v 1.459 2009/07/15 11:26:44 drh Exp $
+** @(#) $Id: sqlite.h.in,v 1.460 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #ifndef _SQLITE3_H_
 #define _SQLITE3_H_
@@ -4331,7 +4331,7 @@ SQLITE_EXPERIMENTAL int sqlite3_create_module_v2(
 */
 struct sqlite3_vtab {
   const sqlite3_module *pModule;  /* The module for this virtual table */
-  int nRef;                       /* Used internally */
+  int nRef;                       /* NO LONGER USED */
   char *zErrMsg;                  /* Error message from sqlite3_mprintf() */
   /* Virtual table implementations will typically add additional fields */
 };
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 5427fc7aa7..9368586a36 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -11,7 +11,7 @@
 *************************************************************************
 ** Internal interface definitions for SQLite.
 **
-** @(#) $Id: sqliteInt.h,v 1.893 2009/07/13 15:52:38 drh Exp $
+** @(#) $Id: sqliteInt.h,v 1.894 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #ifndef _SQLITEINT_H_
 #define _SQLITEINT_H_
@@ -613,6 +613,7 @@ typedef struct TriggerStack TriggerStack;
 typedef struct TriggerStep TriggerStep;
 typedef struct Trigger Trigger;
 typedef struct UnpackedRecord UnpackedRecord;
+typedef struct VTable VTable;
 typedef struct Walker Walker;
 typedef struct WherePlan WherePlan;
 typedef struct WhereInfo WhereInfo;
@@ -839,8 +840,9 @@ struct sqlite3 {
 #ifndef SQLITE_OMIT_VIRTUALTABLE
   Hash aModule;                 /* populated by sqlite3_create_module() */
   Table *pVTab;                 /* vtab with active Connect/Create method */
-  sqlite3_vtab **aVTrans;       /* Virtual tables with open transactions */
+  VTable **aVTrans;             /* Virtual tables with open transactions */
   int nVTrans;                  /* Allocated size of aVTrans */
+  VTable *pDisconnect;    /* Disconnect these in next sqlite3_prepare() */
 #endif
   FuncDefHash aFunc;            /* Hash table of connection functions */
   Hash aCollSeq;                /* All collating sequences */
@@ -905,7 +907,6 @@ struct sqlite3 {
 #define SQLITE_LoadExtension  0x00020000  /* Enable load_extension */
 
 #define SQLITE_RecoveryMode   0x00040000  /* Ignore schema errors */
-#define SQLITE_SharedCache    0x00080000  /* Cache sharing is enabled */
 #define SQLITE_ReverseOrder   0x00100000  /* Reverse unordered SELECTs */
 
 /*
@@ -1114,6 +1115,56 @@ struct CollSeq {
 #define SQLITE_JUMPIFNULL   0x08  /* jumps if either operand is NULL */
 #define SQLITE_STOREP2      0x10  /* Store result in reg[P2] rather than jump */
 
+/*
+** An object of this type is created for each virtual table present in
+** the database schema. 
+**
+** If the database schema is shared, then there is one instance of this
+** structure for each database connection (sqlite3*) that uses the shared
+** schema. This is because each database connection requires its own unique
+** instance of the sqlite3_vtab* handle used to access the virtual table 
+** implementation. sqlite3_vtab* handles can not be shared between 
+** database connections, even when the rest of the in-memory database 
+** schema is shared, as the implementation often stores the database
+** connection handle passed to it via the xConnect() or xCreate() method
+** during initialization internally. This database connection handle may
+** then used by the virtual table implementation to access real tables 
+** within the database. So that they appear as part of the callers 
+** transaction, these accesses need to be made via the same database 
+** connection as that used to execute SQL operations on the virtual table.
+**
+** All VTable objects that correspond to a single table in a shared
+** database schema are initially stored in a linked-list pointed to by
+** the Table.pVTable member variable of the corresponding Table object.
+** When an sqlite3_prepare() operation is required to access the virtual
+** table, it searches the list for the VTable that corresponds to the
+** database connection doing the preparing so as to use the correct
+** sqlite3_vtab* handle in the compiled query.
+**
+** When an in-memory Table object is deleted (for example when the
+** schema is being reloaded for some reason), the VTable objects are not 
+** deleted and the sqlite3_vtab* handles are not xDisconnect()ed 
+** immediately. Instead, they are moved from the Table.pVTable list to
+** another linked list headed by the sqlite3.pDisconnect member of the
+** corresponding sqlite3 structure. They are then deleted/xDisconnected 
+** next time a statement is prepared using said sqlite3*. This is done
+** to avoid deadlock issues involving multiple sqlite3.mutex mutexes.
+** Refer to comments above function sqlite3VtabUnlockList() for an
+** explanation as to why it is safe to add an entry to an sqlite3.pDisconnect
+** list without holding the corresponding sqlite3.mutex mutex.
+**
+** The memory for objects of this type is always allocated by 
+** sqlite3DbMalloc(), using the connection handle stored in VTable.db as 
+** the first argument.
+*/
+struct VTable {
+  sqlite3 *db;              /* Database connection associated with this table */
+  Module *pMod;             /* Pointer to module implementation */
+  sqlite3_vtab *pVtab;      /* Pointer to vtab instance */
+  int nRef;                 /* Number of pointers to this structure */
+  VTable *pNext;            /* Next in linked list (see above) */
+};
+
 /*
 ** Each SQL table is represented in memory by an instance of the
 ** following structure.
@@ -1165,8 +1216,7 @@ struct Table {
   int addColOffset;    /* Offset in CREATE TABLE stmt to add a new column */
 #endif
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  Module *pMod;        /* Pointer to the implementation of the module */
-  sqlite3_vtab *pVtab; /* Pointer to the module instance */
+  VTable *pVTable;     /* List of VTable objects. */
   int nModuleArg;      /* Number of arguments to the module */
   char **azModuleArg;  /* Text of all module args. [0] is module name */
 #endif
@@ -2812,21 +2862,25 @@ void sqlite3AutoLoadExtensions(sqlite3*);
 #endif
 
 #ifdef SQLITE_OMIT_VIRTUALTABLE
-#  define sqlite3VtabClear(X)
+#  define sqlite3VtabClear(Y)
 #  define sqlite3VtabSync(X,Y) SQLITE_OK
 #  define sqlite3VtabRollback(X)
 #  define sqlite3VtabCommit(X)
 #  define sqlite3VtabInSync(db) 0
+#  define sqlite3VtabLock(X) 
+#  define sqlite3VtabUnlock(X)
+#  define sqlite3VtabUnlockList(X)
 #else
    void sqlite3VtabClear(Table*);
    int sqlite3VtabSync(sqlite3 *db, char **);
    int sqlite3VtabRollback(sqlite3 *db);
    int sqlite3VtabCommit(sqlite3 *db);
+   void sqlite3VtabLock(VTable *);
+   void sqlite3VtabUnlock(VTable *);
+   void sqlite3VtabUnlockList(sqlite3*);
 #  define sqlite3VtabInSync(db) ((db)->nVTrans>0 && (db)->aVTrans==0)
 #endif
 void sqlite3VtabMakeWritable(Parse*,Table*);
-void sqlite3VtabLock(sqlite3_vtab*);
-void sqlite3VtabUnlock(sqlite3*, sqlite3_vtab*);
 void sqlite3VtabBeginParse(Parse*, Token*, Token*, Token*);
 void sqlite3VtabFinishParse(Parse*, Token*);
 void sqlite3VtabArgInit(Parse*);
@@ -2834,7 +2888,7 @@ void sqlite3VtabArgExtend(Parse*, Token*);
 int sqlite3VtabCallCreate(sqlite3*, int, const char *, char **);
 int sqlite3VtabCallConnect(Parse*, Table*);
 int sqlite3VtabCallDestroy(sqlite3*, int, const char *);
-int sqlite3VtabBegin(sqlite3 *, sqlite3_vtab *);
+int sqlite3VtabBegin(sqlite3 *, VTable *);
 FuncDef *sqlite3VtabOverloadFunction(sqlite3 *,FuncDef*, int nArg, Expr*);
 void sqlite3InvalidFunction(sqlite3_context*,int,sqlite3_value**);
 int sqlite3TransferBindings(sqlite3_stmt *, sqlite3_stmt *);
@@ -2842,6 +2896,7 @@ int sqlite3Reprepare(Vdbe*);
 void sqlite3ExprListCheckLength(Parse*, ExprList*, const char*);
 CollSeq *sqlite3BinaryCompareCollSeq(Parse *, Expr *, Expr *);
 int sqlite3TempInMemory(const sqlite3*);
+VTable *sqlite3GetVTable(sqlite3*, Table*);
 
 
 
diff --git a/src/update.c b/src/update.c
index fb69799c56..6e33f0b3af 100644
--- a/src/update.c
+++ b/src/update.c
@@ -12,7 +12,7 @@
 ** This file contains C code routines that are called by the parser
 ** to handle UPDATE statements.
 **
-** $Id: update.c,v 1.204 2009/06/27 11:17:35 drh Exp $
+** $Id: update.c,v 1.205 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -155,10 +155,10 @@ void sqlite3Update(
 # define isView 0
 #endif
 
-  if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
+  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
     goto update_cleanup;
   }
-  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
+  if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
     goto update_cleanup;
   }
   aXRef = sqlite3DbMallocRaw(db, sizeof(int) * pTab->nCol );
@@ -631,7 +631,7 @@ static void updateVirtualTable(
   int addr;                 /* Address of top of loop */
   int iReg;                 /* First register in set passed to OP_VUpdate */
   sqlite3 *db = pParse->db; /* Database connection */
-  const char *pVtab = (const char*)pTab->pVtab;
+  const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
   SelectDest dest;
 
   /* Construct the SELECT statement that will find the new values for
@@ -676,7 +676,7 @@ static void updateVirtualTable(
     sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i+1+(pRowid!=0), iReg+2+i);
   }
   sqlite3VtabMakeWritable(pParse, pTab);
-  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVtab, P4_VTAB);
+  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVTab, P4_VTAB);
   sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1);
   sqlite3VdbeJumpHere(v, addr);
   sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
diff --git a/src/vdbe.c b/src/vdbe.c
index 76641c4b6d..e27fbeb48e 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.873 2009/07/22 00:35:24 drh Exp $
+** $Id: vdbe.c,v 1.874 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -5017,13 +5017,13 @@ case OP_TableLock: {
 ** code will be set to SQLITE_LOCKED.
 */
 case OP_VBegin: {
-  sqlite3_vtab *pVtab;
-  pVtab = pOp->p4.pVtab;
-  rc = sqlite3VtabBegin(db, pVtab);
-  if( pVtab ){
+  VTable *pVTab;
+  pVTab = pOp->p4.pVtab;
+  rc = sqlite3VtabBegin(db, pVTab);
+  if( pVTab ){
     sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = pVtab->zErrMsg;
-    pVtab->zErrMsg = 0;
+    p->zErrMsg = pVTab->pVtab->zErrMsg;
+    pVTab->pVtab->zErrMsg = 0;
   }
   break;
 }
@@ -5070,7 +5070,7 @@ case OP_VOpen: {
 
   pCur = 0;
   pVtabCursor = 0;
-  pVtab = pOp->p4.pVtab;
+  pVtab = pOp->p4.pVtab->pVtab;
   pModule = (sqlite3_module *)pVtab->pModule;
   assert(pVtab && pModule);
   if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
@@ -5153,14 +5153,12 @@ case OP_VFilter: {   /* jump */
     }
 
     if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
-    sqlite3VtabLock(pVtab);
     p->inVtabMethod = 1;
     rc = pModule->xFilter(pVtabCursor, iQuery, pOp->p4.z, nArg, apArg);
     p->inVtabMethod = 0;
     sqlite3DbFree(db, p->zErrMsg);
     p->zErrMsg = pVtab->zErrMsg;
     pVtab->zErrMsg = 0;
-    sqlite3VtabUnlock(db, pVtab);
     if( rc==SQLITE_OK ){
       res = pModule->xEof(pVtabCursor);
     }
@@ -5268,14 +5266,12 @@ case OP_VNext: {   /* jump */
   ** some other method is next invoked on the save virtual table cursor.
   */
   if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
-  sqlite3VtabLock(pVtab);
   p->inVtabMethod = 1;
   rc = pModule->xNext(pCur->pVtabCursor);
   p->inVtabMethod = 0;
   sqlite3DbFree(db, p->zErrMsg);
   p->zErrMsg = pVtab->zErrMsg;
   pVtab->zErrMsg = 0;
-  sqlite3VtabUnlock(db, pVtab);
   if( rc==SQLITE_OK ){
     res = pModule->xEof(pCur->pVtabCursor);
   }
@@ -5300,18 +5296,16 @@ case OP_VRename: {
   sqlite3_vtab *pVtab;
   Mem *pName;
 
-  pVtab = pOp->p4.pVtab;
+  pVtab = pOp->p4.pVtab->pVtab;
   pName = &p->aMem[pOp->p1];
   assert( pVtab->pModule->xRename );
   REGISTER_TRACE(pOp->p1, pName);
   assert( pName->flags & MEM_Str );
   if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
-  sqlite3VtabLock(pVtab);
   rc = pVtab->pModule->xRename(pVtab, pName->z);
   sqlite3DbFree(db, p->zErrMsg);
   p->zErrMsg = pVtab->zErrMsg;
   pVtab->zErrMsg = 0;
-  sqlite3VtabUnlock(db, pVtab);
   if( sqlite3SafetyOn(db) ) goto abort_due_to_misuse;
 
   break;
@@ -5351,7 +5345,7 @@ case OP_VUpdate: {
   Mem **apArg;
   Mem *pX;
 
-  pVtab = pOp->p4.pVtab;
+  pVtab = pOp->p4.pVtab->pVtab;
   pModule = (sqlite3_module *)pVtab->pModule;
   nArg = pOp->p2;
   assert( pOp->p4type==P4_VTAB );
@@ -5364,12 +5358,10 @@ case OP_VUpdate: {
       pX++;
     }
     if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
-    sqlite3VtabLock(pVtab);
     rc = pModule->xUpdate(pVtab, nArg, apArg, &rowid);
     sqlite3DbFree(db, p->zErrMsg);
     p->zErrMsg = pVtab->zErrMsg;
     pVtab->zErrMsg = 0;
-    sqlite3VtabUnlock(db, pVtab);
     if( sqlite3SafetyOn(db) ) goto abort_due_to_misuse;
     if( rc==SQLITE_OK && pOp->p1 ){
       assert( nArg>1 && apArg[0] && (apArg[0]->flags&MEM_Null) );
diff --git a/src/vdbe.h b/src/vdbe.h
index 64c440e513..c72ebe1c8e 100644
--- a/src/vdbe.h
+++ b/src/vdbe.h
@@ -15,7 +15,7 @@
 ** or VDBE.  The VDBE implements an abstract machine that runs a
 ** simple program to access and modify the underlying database.
 **
-** $Id: vdbe.h,v 1.141 2009/04/10 00:56:29 drh Exp $
+** $Id: vdbe.h,v 1.142 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #ifndef _SQLITE_VDBE_H_
 #define _SQLITE_VDBE_H_
@@ -58,7 +58,7 @@ struct VdbeOp {
     VdbeFunc *pVdbeFunc;   /* Used when p4type is P4_VDBEFUNC */
     CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
     Mem *pMem;             /* Used when p4type is P4_MEM */
-    sqlite3_vtab *pVtab;   /* Used when p4type is P4_VTAB */
+    VTable *pVtab;         /* Used when p4type is P4_VTAB */
     KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
     int *ai;               /* Used when p4type is P4_INTARRAY */
   } p4;
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 118f4ee2b9..b09c741bf0 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -14,7 +14,7 @@
 ** to version 2.8.7, all this code was combined into the vdbe.c source file.
 ** But that file was getting too big so this subroutines were split out.
 **
-** $Id: vdbeaux.c,v 1.477 2009/07/22 00:35:24 drh Exp $
+** $Id: vdbeaux.c,v 1.478 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -478,6 +478,10 @@ static void freeP4(sqlite3 *db, int p4type, void *p4){
         sqlite3ValueFree((sqlite3_value*)p4);
         break;
       }
+      case P4_VTAB : {
+        sqlite3VtabUnlock((VTable *)p4);
+        break;
+      }
     }
   }
 }
@@ -531,7 +535,7 @@ void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
   db = p->db;
   assert( p->magic==VDBE_MAGIC_INIT );
   if( p->aOp==0 || db->mallocFailed ){
-    if (n != P4_KEYINFO) {
+    if ( n!=P4_KEYINFO && n!=P4_VTAB ) {
       freeP4(db, n, (void*)*(char**)&zP4);
     }
     return;
@@ -576,6 +580,11 @@ void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
   }else if( n==P4_KEYINFO_HANDOFF ){
     pOp->p4.p = (void*)zP4;
     pOp->p4type = P4_KEYINFO;
+  }else if( n==P4_VTAB ){
+    pOp->p4.p = (void*)zP4;
+    pOp->p4type = P4_VTAB;
+    sqlite3VtabLock((VTable *)zP4);
+    assert( ((VTable *)zP4)->db==p->db );
   }else if( n<0 ){
     pOp->p4.p = (void*)zP4;
     pOp->p4type = (signed char)n;
@@ -731,7 +740,7 @@ static char *displayP4(Op *pOp, char *zTemp, int nTemp){
     }
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     case P4_VTAB: {
-      sqlite3_vtab *pVtab = pOp->p4.pVtab;
+      sqlite3_vtab *pVtab = pOp->p4.pVtab->pVtab;
       sqlite3_snprintf(nTemp, zTemp, "vtab:%p:%p", pVtab, pVtab->pModule);
       break;
     }
diff --git a/src/vtab.c b/src/vtab.c
index e870ec043c..e09dcd53a3 100644
--- a/src/vtab.c
+++ b/src/vtab.c
@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file contains code used to help implement virtual tables.
 **
-** $Id: vtab.c,v 1.92 2009/07/01 18:04:21 danielk1977 Exp $
+** $Id: vtab.c,v 1.93 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
 #include "sqliteInt.h"
@@ -27,7 +27,7 @@ static int createModule(
   const sqlite3_module *pModule,  /* The definition of the module */
   void *pAux,                     /* Context pointer for xCreate/xConnect */
   void (*xDestroy)(void *)        /* Module destructor function */
-) {
+){
   int rc, nName;
   Module *pMod;
 
@@ -93,33 +93,128 @@ int sqlite3_create_module_v2(
 ** If a disconnect is attempted while a virtual table is locked,
 ** the disconnect is deferred until all locks have been removed.
 */
-void sqlite3VtabLock(sqlite3_vtab *pVtab){
-  pVtab->nRef++;
+void sqlite3VtabLock(VTable *pVTab){
+  pVTab->nRef++;
+}
+
+
+/*
+** pTab is a pointer to a Table structure representing a virtual-table.
+** Return a pointer to the VTable object used by connection db to access 
+** this virtual-table, if one has been created, or NULL otherwise.
+*/
+VTable *sqlite3GetVTable(sqlite3 *db, Table *pTab){
+  VTable *pVtab;
+  assert( IsVirtual(pTab) );
+  for(pVtab=pTab->pVTable; pVtab && pVtab->db!=db; pVtab=pVtab->pNext);
+  return pVtab;
 }
 
 /*
-** Unlock a virtual table.  When the last lock is removed,
-** disconnect the virtual table.
+** Decrement the ref-count on a virtual table object. When the ref-count
+** reaches zero, call the xDisconnect() method to delete the object.
 */
-void sqlite3VtabUnlock(sqlite3 *db, sqlite3_vtab *pVtab){
-#ifndef SQLITE_DEBUG
-  UNUSED_PARAMETER(db);
-#endif
-  assert( pVtab->nRef>0 );
-  pVtab->nRef--;
-  assert(db);
+void sqlite3VtabUnlock(VTable *pVTab){
+  sqlite3 *db = pVTab->db;
+
+  assert( db );
+  assert( pVTab->nRef>0 );
   assert( sqlite3SafetyCheckOk(db) );
-  if( pVtab->nRef==0 ){
+
+  pVTab->nRef--;
+  if( pVTab->nRef==0 ){
+    sqlite3_vtab *p = pVTab->pVtab;
+    if( p ){
 #ifdef SQLITE_DEBUG
-    if( db->magic==SQLITE_MAGIC_BUSY ){
-      (void)sqlite3SafetyOff(db);
-      pVtab->pModule->xDisconnect(pVtab);
-      (void)sqlite3SafetyOn(db);
-    } else 
+      if( pVTab->db->magic==SQLITE_MAGIC_BUSY ){
+        (void)sqlite3SafetyOff(db);
+        p->pModule->xDisconnect(p);
+        (void)sqlite3SafetyOn(db);
+      } else
 #endif
-    {
-      pVtab->pModule->xDisconnect(pVtab);
+      {
+        p->pModule->xDisconnect(p);
+      }
     }
+    sqlite3DbFree(db, pVTab);
+  }
+}
+
+/*
+** Table p is a virtual table. This function moves all elements in the
+** p->pVTable list to the sqlite3.pDisconnect lists of their associated
+** database connections to be disconnected at the next opportunity. 
+** Except, if argument db is not NULL, then the entry associated with
+** connection db is left in the p->pVTable list.
+*/
+static VTable *vtabDisconnectAll(sqlite3 *db, Table *p){
+  VTable *pRet = 0;
+  VTable *pVTable = p->pVTable;
+  p->pVTable = 0;
+
+  /* Assert that the mutex (if any) associated with the BtShared database 
+  ** that contains table p is held by the caller. See header comments 
+  ** above function sqlite3VtabUnlockList() for an explanation of why
+  ** this makes it safe to access the sqlite3.pDisconnect list of any
+  ** database connection that may have an entry in the p->pVTable list.  */
+  assert( db==0 ||
+    sqlite3BtreeHoldsMutex(db->aDb[sqlite3SchemaToIndex(db, p->pSchema)].pBt) 
+  );
+
+  while( pVTable ){
+    sqlite3 *db2 = pVTable->db;
+    VTable *pNext = pVTable->pNext;
+    assert( db2 );
+    if( db2==db ){
+      pRet = pVTable;
+      p->pVTable = pRet;
+      pRet->pNext = 0;
+    }else{
+      pVTable->pNext = db2->pDisconnect;
+      db2->pDisconnect = pVTable;
+    }
+    pVTable = pNext;
+  }
+
+  assert( !db || pRet );
+  return pRet;
+}
+
+
+/*
+** Disconnect all the virtual table objects in the sqlite3.pDisconnect list.
+**
+** This function may only be called when the mutexes associated with all
+** shared b-tree databases opened using connection db are held by the 
+** caller. This is done to protect the sqlite3.pDisconnect list. The
+** sqlite3.pDisconnect list is accessed only as follows:
+**
+**   1) By this function. In this case, all BtShared mutexes and the mutex
+**      associated with the database handle itself must be held.
+**
+**   2) By function vtabDisconnectAll(), when it adds a VTable entry to
+**      the sqlite3.pDisconnect list. In this case either the BtShared mutex
+**      associated with the database the virtual table is stored in is held
+**      or, if the virtual table is stored in a non-sharable database, then
+**      the database handle mutex is held.
+**
+** As a result, a sqlite3.pDisconnect cannot be accessed simultaneously 
+** by multiple threads. It is thread-safe.
+*/
+void sqlite3VtabUnlockList(sqlite3 *db){
+  VTable *p = db->pDisconnect;
+  db->pDisconnect = 0;
+
+  assert( sqlite3BtreeHoldsAllMutexes(db) );
+  assert( sqlite3_mutex_held(db->mutex) );
+
+  if( p ){
+    sqlite3ExpirePreparedStatements(db);
+    do {
+      VTable *pNext = p->pNext;
+      sqlite3VtabUnlock(p);
+      p = pNext;
+    }while( p );
   }
 }
 
@@ -127,22 +222,24 @@ void sqlite3VtabUnlock(sqlite3 *db, sqlite3_vtab *pVtab){
 ** Clear any and all virtual-table information from the Table record.
 ** This routine is called, for example, just before deleting the Table
 ** record.
+**
+** Since it is a virtual-table, the Table structure contains a pointer
+** to the head of a linked list of VTable structures. Each VTable 
+** structure is associated with a single sqlite3* user of the schema.
+** The reference count of the VTable structure associated with database 
+** connection db is decremented immediately (which may lead to the 
+** structure being xDisconnected and free). Any other VTable structures
+** in the list are moved to the sqlite3.pDisconnect list of the associated 
+** database connection.
 */
 void sqlite3VtabClear(Table *p){
-  sqlite3_vtab *pVtab = p->pVtab;
-  Schema *pSchema = p->pSchema;
-  sqlite3 *db = pSchema ? pSchema->db : 0;
-  if( pVtab ){
-    assert( p->pMod && p->pMod->pModule );
-    sqlite3VtabUnlock(db, pVtab);
-    p->pVtab = 0;
-  }
+  vtabDisconnectAll(0, p);
   if( p->azModuleArg ){
     int i;
     for(i=0; i<p->nModuleArg; i++){
-      sqlite3DbFree(db, p->azModuleArg[i]);
+      sqlite3DbFree(p->dbMem, p->azModuleArg[i]);
     }
-    sqlite3DbFree(db, p->azModuleArg);
+    sqlite3DbFree(p->dbMem, p->azModuleArg);
   }
 }
 
@@ -187,11 +284,6 @@ void sqlite3VtabBeginParse(
   Table *pTable;        /* The new virtual table */
   sqlite3 *db;          /* Database connection */
 
-  if( pParse->db->flags & SQLITE_SharedCache ){
-    sqlite3ErrorMsg(pParse, "Cannot use virtual tables in shared-cache mode");
-    return;
-  }
-
   sqlite3StartTable(pParse, pName1, pName2, 0, 0, 1, 0);
   pTable = pParse->pNewTable;
   if( pTable==0 ) return;
@@ -240,23 +332,13 @@ static void addArgumentToVtab(Parse *pParse){
 ** has been completely parsed.
 */
 void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
-  Table *pTab;        /* The table being constructed */
-  sqlite3 *db;        /* The database connection */
-  char *zModule;      /* The module name of the table: USING modulename */
-  Module *pMod = 0;
+  Table *pTab = pParse->pNewTable;  /* The table being constructed */
+  sqlite3 *db = pParse->db;         /* The database connection */
 
+  if( pTab==0 ) return;
   addArgumentToVtab(pParse);
   pParse->sArg.z = 0;
-
-  /* Lookup the module name. */
-  pTab = pParse->pNewTable;
-  if( pTab==0 ) return;
-  db = pParse->db;
   if( pTab->nModuleArg<1 ) return;
-  zModule = pTab->azModuleArg[0];
-  pMod = (Module*)sqlite3HashFind(&db->aModule, zModule,
-                                  sqlite3Strlen30(zModule));
-  pTab->pMod = pMod;
   
   /* If the CREATE VIRTUAL TABLE statement is being entered for the
   ** first time (in other words if the virtual table is actually being
@@ -307,9 +389,10 @@ void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
   }
 
   /* If we are rereading the sqlite_master table create the in-memory
-  ** record of the table. If the module has already been registered,
-  ** also call the xConnect method here.
-  */
+  ** record of the table. The xConnect() method is not called until
+  ** the first time the virtual table is used in an SQL statement. This
+  ** allows a schema that contains virtual tables to be loaded before
+  ** the required virtual table implementations are registered.  */
   else {
     Table *pOld;
     Schema *pSchema = pTab->pSchema;
@@ -363,9 +446,8 @@ static int vtabCallConstructor(
   int (*xConstruct)(sqlite3*,void*,int,const char*const*,sqlite3_vtab**,char**),
   char **pzErr
 ){
+  VTable *pVTable;
   int rc;
-  int rc2;
-  sqlite3_vtab *pVtab = 0;
   const char *const*azArg = (const char *const*)pTab->azModuleArg;
   int nArg = pTab->nModuleArg;
   char *zErr = 0;
@@ -375,22 +457,23 @@ static int vtabCallConstructor(
     return SQLITE_NOMEM;
   }
 
+  pVTable = sqlite3DbMallocZero(db, sizeof(VTable));
+  if( !pVTable ){
+    sqlite3DbFree(db, zModuleName);
+    return SQLITE_NOMEM;
+  }
+  pVTable->db = db;
+  pVTable->pMod = pMod;
+
   assert( !db->pVTab );
   assert( xConstruct );
-
   db->pVTab = pTab;
-  rc = sqlite3SafetyOff(db);
-  assert( rc==SQLITE_OK );
-  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVtab, &zErr);
-  rc2 = sqlite3SafetyOn(db);
+
+  /* Invoke the virtual table constructor */
+  (void)sqlite3SafetyOff(db);
+  rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVTable->pVtab, &zErr);
+  (void)sqlite3SafetyOn(db);
   if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
-  /* Justification of ALWAYS():  A correct vtab constructor must allocate
-  ** the sqlite3_vtab object if successful. */
-  if( rc==SQLITE_OK && ALWAYS(pVtab) ){
-    pVtab->pModule = pMod->pModule;
-    pVtab->nRef = 1;
-    pTab->pVtab = pVtab;
-  }
 
   if( SQLITE_OK!=rc ){
     if( zErr==0 ){
@@ -399,54 +482,61 @@ static int vtabCallConstructor(
       *pzErr = sqlite3MPrintf(db, "%s", zErr);
       sqlite3DbFree(db, zErr);
     }
-  }else if( db->pVTab ){
-    const char *zFormat = "vtable constructor did not declare schema: %s";
-    *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
-    rc = SQLITE_ERROR;
-  } 
-  if( rc==SQLITE_OK ){
-    rc = rc2;
-  }
-  db->pVTab = 0;
-  sqlite3DbFree(db, zModuleName);
+    sqlite3DbFree(db, pVTable);
+  }else if( ALWAYS(pVTable->pVtab) ){
+    /* Justification of ALWAYS():  A correct vtab constructor must allocate
+    ** the sqlite3_vtab object if successful.  */
+    pVTable->pVtab->pModule = pMod->pModule;
+    pVTable->nRef = 1;
+    if( db->pVTab ){
+      const char *zFormat = "vtable constructor did not declare schema: %s";
+      *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
+      sqlite3VtabUnlock(pVTable);
+      rc = SQLITE_ERROR;
+    }else{
+      int iCol;
+      /* If everything went according to plan, link the new VTable structure
+      ** into the linked list headed by pTab->pVTable. Then loop through the 
+      ** columns of the table to see if any of them contain the token "hidden".
+      ** If so, set the Column.isHidden flag and remove the token from
+      ** the type string.  */
+      pVTable->pNext = pTab->pVTable;
+      pTab->pVTable = pVTable;
 
-  /* If everything went according to plan, loop through the columns
-  ** of the table to see if any of them contain the token "hidden".
-  ** If so, set the Column.isHidden flag and remove the token from
-  ** the type string.
-  */
-  if( rc==SQLITE_OK ){
-    int iCol;
-    for(iCol=0; iCol<pTab->nCol; iCol++){
-      char *zType = pTab->aCol[iCol].zType;
-      int nType;
-      int i = 0;
-      if( !zType ) continue;
-      nType = sqlite3Strlen30(zType);
-      if( sqlite3StrNICmp("hidden", zType, 6) || (zType[6] && zType[6]!=' ') ){
-        for(i=0; i<nType; i++){
-          if( (0==sqlite3StrNICmp(" hidden", &zType[i], 7))
-           && (zType[i+7]=='\0' || zType[i+7]==' ')
-          ){
-            i++;
-            break;
+      for(iCol=0; iCol<pTab->nCol; iCol++){
+        char *zType = pTab->aCol[iCol].zType;
+        int nType;
+        int i = 0;
+        if( !zType ) continue;
+        nType = sqlite3Strlen30(zType);
+        if( sqlite3StrNICmp("hidden", zType, 6)||(zType[6] && zType[6]!=' ') ){
+          for(i=0; i<nType; i++){
+            if( (0==sqlite3StrNICmp(" hidden", &zType[i], 7))
+             && (zType[i+7]=='\0' || zType[i+7]==' ')
+            ){
+              i++;
+              break;
+            }
           }
         }
-      }
-      if( i<nType ){
-        int j;
-        int nDel = 6 + (zType[i+6] ? 1 : 0);
-        for(j=i; (j+nDel)<=nType; j++){
-          zType[j] = zType[j+nDel];
+        if( i<nType ){
+          int j;
+          int nDel = 6 + (zType[i+6] ? 1 : 0);
+          for(j=i; (j+nDel)<=nType; j++){
+            zType[j] = zType[j+nDel];
+          }
+          if( zType[i]=='\0' && i>0 ){
+            assert(zType[i-1]==' ');
+            zType[i-1] = '\0';
+          }
+          pTab->aCol[iCol].isHidden = 1;
         }
-        if( zType[i]=='\0' && i>0 ){
-          assert(zType[i-1]==' ');
-          zType[i-1] = '\0';
-        }
-        pTab->aCol[iCol].isHidden = 1;
       }
     }
   }
+
+  sqlite3DbFree(db, zModuleName);
+  db->pVTab = 0;
   return rc;
 }
 
@@ -458,20 +548,25 @@ static int vtabCallConstructor(
 ** This call is a no-op if table pTab is not a virtual table.
 */
 int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
+  sqlite3 *db = pParse->db;
+  const char *zMod;
   Module *pMod;
-  int rc = SQLITE_OK;
+  int rc;
 
   assert( pTab );
-  if( (pTab->tabFlags & TF_Virtual)==0 || pTab->pVtab ){
+  if( (pTab->tabFlags & TF_Virtual)==0 || sqlite3GetVTable(db, pTab) ){
     return SQLITE_OK;
   }
 
-  pMod = pTab->pMod;
+  /* Locate the required virtual table module */
+  zMod = pTab->azModuleArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod, sqlite3Strlen30(zMod));
+
   if( !pMod ){
     const char *zModule = pTab->azModuleArg[0];
     sqlite3ErrorMsg(pParse, "no such module: %s", zModule);
     rc = SQLITE_ERROR;
-  } else {
+  }else{
     char *zErr = 0;
     sqlite3 *db = pParse->db;
     rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xConnect, &zErr);
@@ -485,14 +580,14 @@ int sqlite3VtabCallConnect(Parse *pParse, Table *pTab){
 }
 
 /*
-** Add the virtual table pVtab to the array sqlite3.aVTrans[].
+** Add the virtual table pVTab to the array sqlite3.aVTrans[].
 */
-static int addToVTrans(sqlite3 *db, sqlite3_vtab *pVtab){
+static int addToVTrans(sqlite3 *db, VTable *pVTab){
   const int ARRAY_INCR = 5;
 
   /* Grow the sqlite3.aVTrans array if required */
   if( (db->nVTrans%ARRAY_INCR)==0 ){
-    sqlite3_vtab **aVTrans;
+    VTable **aVTrans;
     int nBytes = sizeof(sqlite3_vtab *) * (db->nVTrans + ARRAY_INCR);
     aVTrans = sqlite3DbRealloc(db, (void *)db->aVTrans, nBytes);
     if( !aVTrans ){
@@ -503,8 +598,8 @@ static int addToVTrans(sqlite3 *db, sqlite3_vtab *pVtab){
   }
 
   /* Add pVtab to the end of sqlite3.aVTrans */
-  db->aVTrans[db->nVTrans++] = pVtab;
-  sqlite3VtabLock(pVtab);
+  db->aVTrans[db->nVTrans++] = pVTab;
+  sqlite3VtabLock(pVTab);
   return SQLITE_OK;
 }
 
@@ -520,19 +615,21 @@ int sqlite3VtabCallCreate(sqlite3 *db, int iDb, const char *zTab, char **pzErr){
   int rc = SQLITE_OK;
   Table *pTab;
   Module *pMod;
-  const char *zModule;
+  const char *zMod;
 
   pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);
-  assert(pTab && (pTab->tabFlags & TF_Virtual)!=0 && !pTab->pVtab);
-  pMod = pTab->pMod;
-  zModule = pTab->azModuleArg[0];
+  assert( pTab && (pTab->tabFlags & TF_Virtual)!=0 && !pTab->pVTable );
+
+  /* Locate the required virtual table module */
+  zMod = pTab->azModuleArg[0];
+  pMod = (Module*)sqlite3HashFind(&db->aModule, zMod, sqlite3Strlen30(zMod));
 
   /* If the module has been registered and includes a Create method, 
   ** invoke it now. If the module has not been registered, return an 
   ** error. Otherwise, do nothing.
   */
   if( !pMod ){
-    *pzErr = sqlite3MPrintf(db, "no such module: %s", zModule);
+    *pzErr = sqlite3MPrintf(db, "no such module: %s", zMod);
     rc = SQLITE_ERROR;
   }else{
     rc = vtabCallConstructor(db, pTab, pMod, pMod->pModule->xCreate, pzErr);
@@ -540,8 +637,8 @@ int sqlite3VtabCallCreate(sqlite3 *db, int iDb, const char *zTab, char **pzErr){
 
   /* Justification of ALWAYS():  The xConstructor method is required to
   ** create a valid sqlite3_vtab if it returns SQLITE_OK. */
-  if( rc==SQLITE_OK && ALWAYS(pTab->pVtab) ){
-      rc = addToVTrans(db, pTab->pVtab);
+  if( rc==SQLITE_OK && ALWAYS(sqlite3GetVTable(db, pTab)) ){
+      rc = addToVTrans(db, sqlite3GetVTable(db, pTab));
   }
 
   return rc;
@@ -566,7 +663,7 @@ int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
     sqlite3_mutex_leave(db->mutex);
     return SQLITE_MISUSE;
   }
-  assert((pTab->tabFlags & TF_Virtual)!=0 && pTab->nCol==0 && pTab->aCol==0);
+  assert( (pTab->tabFlags & TF_Virtual)!=0 );
 
   pParse = sqlite3StackAllocZero(db, sizeof(*pParse));
   if( pParse==0 ){
@@ -581,10 +678,12 @@ int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
         !pParse->pNewTable->pSelect && 
         (pParse->pNewTable->tabFlags & TF_Virtual)==0
     ){
-      pTab->aCol = pParse->pNewTable->aCol;
-      pTab->nCol = pParse->pNewTable->nCol;
-      pParse->pNewTable->nCol = 0;
-      pParse->pNewTable->aCol = 0;
+      if( !pTab->aCol ){
+        pTab->aCol = pParse->pNewTable->aCol;
+        pTab->nCol = pParse->pNewTable->nCol;
+        pParse->pNewTable->nCol = 0;
+        pParse->pNewTable->aCol = 0;
+      }
       db->pVTab = 0;
     } else {
       sqlite3Error(db, SQLITE_ERROR, zErr);
@@ -618,21 +717,20 @@ int sqlite3VtabCallDestroy(sqlite3 *db, int iDb, const char *zTab){
   Table *pTab;
 
   pTab = sqlite3FindTable(db, zTab, db->aDb[iDb].zName);
-  if( ALWAYS(pTab!=0 && pTab->pVtab!=0) ){
-    int (*xDestroy)(sqlite3_vtab *pVTab) = pTab->pMod->pModule->xDestroy;
+  if( ALWAYS(pTab!=0 && pTab->pVTable!=0) ){
+    VTable *p = vtabDisconnectAll(db, pTab);
+
     rc = sqlite3SafetyOff(db);
     assert( rc==SQLITE_OK );
-    rc = xDestroy(pTab->pVtab);
+    rc = p->pMod->pModule->xDestroy(p->pVtab);
     (void)sqlite3SafetyOn(db);
+
+    /* Remove the sqlite3_vtab* from the aVTrans[] array, if applicable */
     if( rc==SQLITE_OK ){
-      int i;
-      for(i=0; i<db->nVTrans; i++){
-        if( db->aVTrans[i]==pTab->pVtab ){
-          db->aVTrans[i] = db->aVTrans[--db->nVTrans];
-          break;
-        }
-      }
-      pTab->pVtab = 0;
+      assert( pTab->pVTable==p && p->pNext==0 );
+      p->pVtab = 0;
+      pTab->pVTable = 0;
+      sqlite3VtabUnlock(p);
     }
   }
 
@@ -651,13 +749,14 @@ static void callFinaliser(sqlite3 *db, int offset){
   int i;
   if( db->aVTrans ){
     for(i=0; i<db->nVTrans; i++){
-      sqlite3_vtab *pVtab = db->aVTrans[i];
-      int (*x)(sqlite3_vtab *);
-
-      assert( pVtab!=0 );
-      x = *(int (**)(sqlite3_vtab *))((char *)pVtab->pModule + offset);
-      if( x ) x(pVtab);
-      sqlite3VtabUnlock(db, pVtab);
+      VTable *pVTab = db->aVTrans[i];
+      sqlite3_vtab *p = pVTab->pVtab;
+      if( p ){
+        int (*x)(sqlite3_vtab *);
+        x = *(int (**)(sqlite3_vtab *))((char *)p->pModule + offset);
+        if( x ) x(p);
+      }
+      sqlite3VtabUnlock(pVTab);
     }
     sqlite3DbFree(db, db->aVTrans);
     db->nVTrans = 0;
@@ -677,16 +776,14 @@ int sqlite3VtabSync(sqlite3 *db, char **pzErrmsg){
   int i;
   int rc = SQLITE_OK;
   int rcsafety;
-  sqlite3_vtab **aVTrans = db->aVTrans;
+  VTable **aVTrans = db->aVTrans;
 
   rc = sqlite3SafetyOff(db);
   db->aVTrans = 0;
   for(i=0; rc==SQLITE_OK && i<db->nVTrans; i++){
-    sqlite3_vtab *pVtab = aVTrans[i];
     int (*x)(sqlite3_vtab *);
-    assert( pVtab!=0 );
-    x = pVtab->pModule->xSync;
-    if( x ){
+    sqlite3_vtab *pVtab = aVTrans[i]->pVtab;
+    if( pVtab && (x = pVtab->pModule->xSync)!=0 ){
       rc = x(pVtab);
       sqlite3DbFree(db, *pzErrmsg);
       *pzErrmsg = pVtab->zErrMsg;
@@ -728,7 +825,7 @@ int sqlite3VtabCommit(sqlite3 *db){
 ** If the xBegin call is successful, place the sqlite3_vtab pointer
 ** in the sqlite3.aVTrans array.
 */
-int sqlite3VtabBegin(sqlite3 *db, sqlite3_vtab *pVtab){
+int sqlite3VtabBegin(sqlite3 *db, VTable *pVTab){
   int rc = SQLITE_OK;
   const sqlite3_module *pModule;
 
@@ -740,10 +837,10 @@ int sqlite3VtabBegin(sqlite3 *db, sqlite3_vtab *pVtab){
   if( sqlite3VtabInSync(db) ){
     return SQLITE_LOCKED;
   }
-  if( !pVtab ){
+  if( !pVTab ){
     return SQLITE_OK;
   } 
-  pModule = pVtab->pModule;
+  pModule = pVTab->pVtab->pModule;
 
   if( pModule->xBegin ){
     int i;
@@ -751,15 +848,15 @@ int sqlite3VtabBegin(sqlite3 *db, sqlite3_vtab *pVtab){
 
     /* If pVtab is already in the aVTrans array, return early */
     for(i=0; i<db->nVTrans; i++){
-      if( db->aVTrans[i]==pVtab ){
+      if( db->aVTrans[i]==pVTab ){
         return SQLITE_OK;
       }
     }
 
     /* Invoke the xBegin method */
-    rc = pModule->xBegin(pVtab);
+    rc = pModule->xBegin(pVTab->pVtab);
     if( rc==SQLITE_OK ){
-      rc = addToVTrans(db, pVtab);
+      rc = addToVTrans(db, pVTab);
     }
   }
   return rc;
@@ -801,7 +898,7 @@ FuncDef *sqlite3VtabOverloadFunction(
   pTab = pExpr->pTab;
   if( NEVER(pTab==0) ) return pDef;
   if( (pTab->tabFlags & TF_Virtual)==0 ) return pDef;
-  pVtab = pTab->pVtab;
+  pVtab = sqlite3GetVTable(db, pTab)->pVtab;
   assert( pVtab!=0 );
   assert( pVtab->pModule!=0 );
   pMod = (sqlite3_module *)pVtab->pModule;
diff --git a/src/where.c b/src/where.c
index efadfc1b8b..4416b8d81b 100644
--- a/src/where.c
+++ b/src/where.c
@@ -16,7 +16,7 @@
 ** so is applicable.  Because this module is responsible for selecting
 ** indices, you might also think of this module as the "query optimizer".
 **
-** $Id: where.c,v 1.408 2009/06/16 14:15:22 shane Exp $
+** $Id: where.c,v 1.409 2009/07/24 17:58:53 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -1726,7 +1726,7 @@ static sqlite3_index_info *allocateIndexInfo(
 ** that this is required.
 */
 static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
-  sqlite3_vtab *pVtab = pTab->pVtab;
+  sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
   int i;
   int rc;
 
@@ -1823,7 +1823,7 @@ static void bestVirtualIndex(
   ** sqlite3ViewGetColumnNames() would have picked up the error. 
   */
   assert( pTab->azModuleArg && pTab->azModuleArg[0] );
-  assert( pTab->pVtab );
+  assert( sqlite3GetVTable(pParse->db, pTab) );
 
   /* Set the aConstraint[].usable fields and initialize all 
   ** output variables to zero.
@@ -3404,13 +3404,13 @@ WhereInfo *sqlite3WhereBegin(
 #endif /* SQLITE_OMIT_EXPLAIN */
     pTabItem = &pTabList->a[pLevel->iFrom];
     pTab = pTabItem->pTab;
-    iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
+    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
     if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
+      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
       int iCur = pTabItem->iCursor;
-      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0,
-                        (const char*)pTab->pVtab, P4_VTAB);
+      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
     }else
 #endif
     if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
diff --git a/test/vtab_shared.test b/test/vtab_shared.test
index cfc48d9a6f..e195ef232b 100644
--- a/test/vtab_shared.test
+++ b/test/vtab_shared.test
@@ -11,7 +11,7 @@
 # This file tests interactions between the virtual table and
 # shared-schema functionality.
 #
-# $Id: vtab_shared.test,v 1.2 2008/03/19 13:03:34 drh Exp $
+# $Id: vtab_shared.test,v 1.3 2009/07/24 17:58:53 danielk1977 Exp $
 
 set testdir [file dirname $argv0]
 source $testdir/tester.tcl
@@ -23,39 +23,207 @@ ifcapable !vtab||!shared_cache {
 
 db close
 sqlite3_enable_shared_cache 1
-sqlite3 db test.db
-
-do_test vtab_shared-1.0 {
-  register_echo_module [sqlite3_connection_pointer db]
-  catchsql {
-    CREATE TABLE t0(a, b, c);
-    CREATE VIRTUAL TABLE t1 USING echo(t0);
-  }
-} {1 {Cannot use virtual tables in shared-cache mode}}
-
-db close
-sqlite3_enable_shared_cache 0
-sqlite3 db test.db
+sqlite3 db  test.db
+sqlite3 db2 test.db
 
 do_test vtab_shared-1.1 {
   register_echo_module [sqlite3_connection_pointer db]
-  catchsql {
+  execsql {
+    CREATE TABLE t0(a, b, c);
+    INSERT INTO t0 VALUES(1, 2, 3);
     CREATE VIRTUAL TABLE t1 USING echo(t0);
   }
-} {0 {}}
-
-db close
-sqlite3_enable_shared_cache 1
-sqlite3 db test.db
+} {}
 
 do_test vtab_shared-1.2 {
-  register_echo_module [sqlite3_connection_pointer db]
-  catchsql {
+  execsql { SELECT * FROM t1 } db
+} {1 2 3}
+
+# Fails because the 'echo' module has not been registered with connection db2
+do_test vtab_shared-1.3 {
+  catchsql { SELECT * FROM t1 } db2
+} {1 {no such module: echo}}
+
+do_test vtab_shared-1.4 {
+  execsql { SELECT * FROM t0 } db2
+} {1 2 3}
+
+do_test vtab_shared-1.5 {
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { SELECT * FROM t1 } db
+} {1 2 3}
+
+# Works after the module is registered with db2
+do_test vtab_shared-1.6 {
+  execsql { SELECT * FROM t1 } db2
+} {1 2 3}
+
+# Set a write-lock on table t0 using connection [db]. Then try to read from
+# virtual table t1 using [db2]. That this returns an SQLITE_LOCKED error
+# shows that the correct sqlite3_vtab is being used.
+#
+do_test vtab_shared-1.8.1 {
+  execsql { 
+    BEGIN;
+    INSERT INTO t1 VALUES(4, 5, 6);
     SELECT * FROM t1;
   }
-} [list 1 \
-  {malformed database schema (t1) - Cannot use virtual tables in shared-cache mode}]
+} {1 2 3 4 5 6}
+do_test vtab_shared-1.8.2 {
+  catchsql { SELECT * FROM t1 } db2
+} {1 {database table is locked}}
+do_test vtab_shared-1.8.3 {
+  catchsql { SELECT *  FROM t0 } db2
+} {1 {database table is locked: t0}}
+do_test vtab_shared-1.8.4 {
+  execsql { SELECT * FROM t0 } db
+} {1 2 3 4 5 6}
+do_test vtab_shared-1.8.5 {
+  execsql { COMMIT } db
+  execsql { SELECT *  FROM t1 } db2
+} {1 2 3 4 5 6}
+
+# While a SELECT is active on virtual table t1 via connection [db], close 
+# [db2]. This causes the schema to be reset internally. Verify that this
+# does not cause a problem.
+#
+foreach {iTest dbSelect dbClose} {
+  1 db  db2
+  2 db  db2
+  3 db2 db
+} {
+  do_test vtab_shared-1.9.$iTest {
+    set res [list]
+    $dbSelect eval { SELECT * FROM t1 } {
+      if {$a == 1} {$dbClose close}
+      lappend res $a $b $c
+    }
+    sqlite3 $dbClose test.db
+    register_echo_module [sqlite3_connection_pointer $dbClose]
+    set res
+  } {1 2 3 4 5 6}
+}
+
+# Ensure that it is not possible for one connection to DROP a virtual
+# table while a second connection is reading from the database.
+#
+do_test vtab_shared-1.10 {
+  db eval { SELECT * FROM t1 } {
+    set error [catchsql { DROP TABLE t1 } db2]
+    break
+  }
+  set error
+} {1 {database table is locked: sqlite_master}}
+
+do_test vtab_shared-1.11 {
+breakpoint
+  execsql {
+    CREATE VIRTUAL TABLE t2 USING echo(t0);
+    CREATE VIRTUAL TABLE t3 USING echo(t0);
+  }
+  execsql { SELECT * FROM t3 } db2
+} {1 2 3 4 5 6}
+
+do_test vtab_shared-1.12.1 {
+  db close
+  execsql { 
+    SELECT * FROM t1 UNION ALL
+    SELECT * FROM t2 UNION ALL
+    SELECT * FROM t3 
+  } db2
+} {1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6}
+do_test vtab_shared-1.12.2 {
+  sqlite3 db test.db
+  register_echo_module [sqlite3_connection_pointer db]
+  execsql { 
+    SELECT * FROM t1 UNION ALL
+    SELECT * FROM t2 UNION ALL
+    SELECT * FROM t3 
+  } db
+} {1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6}
+
+# Try a rename or two.
+#
+do_test vtab_shared-1.13.1 {
+  execsql { ALTER TABLE t1 RENAME TO t4 }
+  execsql { SELECT * FROM t4 } db
+} {1 2 3 4 5 6}
+do_test vtab_shared-1.13.2 {
+  execsql { SELECT * FROM t4 } db2
+} {1 2 3 4 5 6}
+do_test vtab_shared-1.13.3 {
+  execsql { ALTER TABLE t2 RENAME TO t5 }
+  execsql { SELECT * FROM t4 } db2
+} {1 2 3 4 5 6}
+
+# Try an UPDATE/INSERT/DELETE on a shared vtab as the first statement after a
+# schema is loaded.
+do_test vtab_shared_1.14.1 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { SELECT * FROM t3 }
+} {1 2 3 4 5 6}
+do_test vtab_shared_1.14.2 {
+  execsql { 
+    UPDATE t3 SET c = 'six' WHERE c = 6;
+    SELECT * FROM t3;
+  } db2
+} {1 2 3 4 5 six}
+do_test vtab_shared_1.14.3 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { SELECT * FROM t3 }
+} {1 2 3 4 5 six}
+do_test vtab_shared_1.14.4 {
+  execsql { 
+    DELETE FROM t3 WHERE c = 'six';
+    SELECT * FROM t3;
+  } db2
+} {1 2 3}
+do_test vtab_shared_1.14.5 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { SELECT * FROM t3 }
+} {1 2 3}
+do_test vtab_shared_1.14.6 {
+  execsql { 
+    INSERT INTO t3 VALUES(4, 5, 6);
+    SELECT * FROM t3;
+  } db2
+} {1 2 3 4 5 6}
+
+do_test vtab_shared_1.15.1 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { 
+    UPDATE t3 SET c = 'six' WHERE c = 6;
+    SELECT * FROM t3;
+  } db2
+} {1 2 3 4 5 six}
+do_test vtab_shared_1.15.2 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { 
+    DELETE FROM t3 WHERE c = 'six';
+    SELECT * FROM t3;
+  } db2
+} {1 2 3}
+do_test vtab_shared_1.15.3 {
+  db2 close
+  sqlite3 db2 test.db
+  register_echo_module [sqlite3_connection_pointer db2]
+  execsql { 
+    INSERT INTO t3 VALUES(4, 5, 6);
+    SELECT * FROM t3;
+  }
+} {1 2 3 4 5 6}
 
 db close
+db2 close
 sqlite3_enable_shared_cache 0
 finish_test