Cause opening a transaction on a sharable b-tree module automatically obtain a read-lock on page 1. This means there is no way for sqlite3BtreeGetMeta() to fail. (CVS 6836)

FossilOrigin-Name: e3c055f167f895ae45858de9d9d8a264df2f36b6

manifest

@@ -1,5 +1,5 @@
-C Fix\sfor\scompilation\swith\sOMIT_AUTOVACUUM\sdefined.\sTicket\s#3940.\s(CVS\s6835)
+C Cause\sopening\sa\stransaction\son\sa\ssharable\sb-tree\smodule\sautomatically\sobtain\sa\sread-lock\son\spage\s1.\sThis\smeans\sthere\sis\sno\sway\sfor\ssqlite3BtreeGetMeta()\sto\sfail.\s(CVS\s6836)
-D 2009-07-02T05:23:26
+D 2009-07-02T07:47:33
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 8b8fb7823264331210cddf103831816c286ba446
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -103,12 +103,12 @@ F src/alter.c 95f41d957f56407aac6224041ca5b954042318d1
 F src/analyze.c e239496cfb5394ac8867f1c112905ddab8d01cd9
 F src/attach.c 13995348fc5a26cdd136a50806faf292aabc173f
 F src/auth.c 98db07c2088455797678eb1031f42d4d94d18a71
-F src/backup.c ff50af53184a5fd7bdee4d620b5dabef74717c79
+F src/backup.c 97a3859d8585eb4fcb1e81a795cf4b3fdd82f30f
 F src/bitvec.c 0ef0651714728055d43de7a4cdd95e703fac0119
 F src/btmutex.c 9b899c0d8df3bd68f527b0afe03088321b696d3c
-F src/btree.c aff035e89ae885ab64acaf339d10411a2c79829b
+F src/btree.c b739b9659c07d2b9d20f0e8f51ae0cc7f995e039
-F src/btree.h f70b694e8c163227369a66863b01fbff9009f323
+F src/btree.h 8cae6364735a5cb2d577ddb23fa6d0e655a4b931
-F src/btreeInt.h 55346bc14b939ad41b297942e8b1b581e960fb99
+F src/btreeInt.h b31e5ac04181c7e2892c33ab06228c551df6233c
 F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
 F src/callback.c cb68b21b0d4ae7d11ae0e487933bce3323784dcf
 F src/complete.c 5ad5c6cd4548211867c204c41a126d73a9fbcea0
@@ -152,8 +152,8 @@ F src/parse.y c48ce2025d848bbd1995f811e74dced8ab30abe6
 F src/pcache.c 395f752a13574120bd7513a400ba02a265aaa76d
 F src/pcache.h 9b927ccc5a538e31b4c3bc7eec4f976db42a1324
 F src/pcache1.c 97e7e8e6e34026fb43b47d08532b0c02e959c26c
-F src/pragma.c 1774ff8e2f167368225108489b1c9d123aa13257
+F src/pragma.c 9eb44ac1d3dc1ac3ea4f444abe1a10ae8acaa16c
-F src/prepare.c 3db796d75a786e55cfcb43d46d7145f87b672b76
+F src/prepare.c e8d8996900d4b7b183622dd2fe2286e1ff0ad37f
 F src/printf.c 508a1c59433353552b6553cba175eaa7331f8fc1
 F src/random.c 676b9d7ac820fe81e6fb2394ac8c10cff7f38628
 F src/resolve.c 4a61d03e49b15440878096e6030863fc628828f0
@@ -169,7 +169,7 @@ F src/table.c cc86ad3d6ad54df7c63a3e807b5783c90411a08d
 F src/tclsqlite.c d3195e0738c101a155404ecdb1cd9532a2fd34f2
 F src/test1.c c8f9358879876660b721369f576bf6e4ac5b9210
 F src/test2.c d73e4a490349245fb196b990b80684513e0ceaee
-F src/test3.c 1e1778ca7e0234c9eb329ac6a5729067b822f3d5
+F src/test3.c 56750fb15ec9430b3ddb343df727bc164462a706
 F src/test4.c f79ab52d27ff49b784b631a42e2ccd52cfd5c84c
 F src/test5.c 162a1cea2105a2c460a3f39fa6919617b562a288
 F src/test6.c 1a0a7a1f179469044b065b4a88aab9faee114101
@@ -202,13 +202,13 @@ F src/trigger.c c07c5157c58fcdb704f65d5f5e4775276e45bb8b
 F src/update.c a1bbe774bce495d62dce3df3f42a5f04c1de173a
 F src/utf.c 9541d28f40441812c0b40f00334372a0542c00ff
 F src/util.c 861d5b5c58be4921f0a254489ea94cb15f550ef8
-F src/vacuum.c 0e14f371ea3326c6b8cfba257286d798cd20db59
+F src/vacuum.c 3fe0eebea6d2311c1c2ab2962887d11f7a4dcfb0
-F src/vdbe.c f2462fdb71b8dfd788e2be1228b1b6c1b702ea80
+F src/vdbe.c 7e5781773b62c4ef1569e58340f2ca9a034a08b5
 F src/vdbe.h 35a648bc3279a120da24f34d9a25213ec15daf8a
 F src/vdbeInt.h 831c254a6eef237ef4664c8381a0137586567007
 F src/vdbeapi.c 0ab8ada7260b32031ca97f338caecf0812460624
 F src/vdbeaux.c 3773217a73f93fb292d264b3b1da98c179a0f2f0
-F src/vdbeblob.c f3d3151d8ddfe9fed288f9e2c98c96e12e914fbb
+F src/vdbeblob.c a3f3e0e877fc64ea50165eec2855f5ada4477611
 F src/vdbemem.c 1618f685d19b4bcc96e40b3c478487bafd2ae246
 F src/vtab.c 00902f289521041712fb0293d0bf8688c7af8e48
 F src/walker.c 1edca756275f158b80f20eb6f104c8d3fcc96a04
@@ -738,7 +738,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P a00aeec21cca7ccf19d4cdef618149aa2773c005
+P 8f0591ae98c2125a4922933496f4412aee8ab86e
-R 5fe9e3bafbc544bd46fe048a3e0db33e
+R 2a84fbc1846890230c75f17318268fe4
 U danielk1977
-Z b3ae67dabd40a49c30f3f7417027c9a9
+Z 37d78b0a7f7b710a92735d2117f44c5f

manifest.uuid

@@ -1 +1 @@
-8f0591ae98c2125a4922933496f4412aee8ab86e
+e3c055f167f895ae45858de9d9d8a264df2f36b6

src/backup.c

@@ -12,7 +12,7 @@
 ** This file contains the implementation of the sqlite3_backup_XXX() 
 ** API functions and the related features.
 **
-** $Id: backup.c,v 1.17 2009/06/03 11:25:07 danielk1977 Exp $
+** $Id: backup.c,v 1.18 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "btreeInt.h"
@@ -318,7 +318,7 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
      && SQLITE_OK==(rc = sqlite3BtreeBeginTrans(p->pDest, 2)) 
     ){
       p->bDestLocked = 1;
-      rc = sqlite3BtreeGetMeta(p->pDest, BTREE_SCHEMA_VERSION, &p->iDestSchema);
+      sqlite3BtreeGetMeta(p->pDest, BTREE_SCHEMA_VERSION, &p->iDestSchema);
     }
 
     /* If there is no open read-transaction on the source database, open

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.647 2009/07/02 05:23:26 danielk1977 Exp $
+** $Id: btree.c,v 1.648 2009/07/02 07:47:33 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -366,7 +366,10 @@ static void clearAllSharedCacheTableLocks(Btree *p){
     assert( pLock->pBtree->inTrans>=pLock->eLock );
     if( pLock->pBtree==p ){
       *ppIter = pLock->pNext;
-      sqlite3_free(pLock);
+      assert( pLock->iTable!=1 || pLock==&p->lock );
+      if( pLock->iTable!=1 ){
+        sqlite3_free(pLock);
+      }
     }else{
       ppIter = &pLock->pNext;
     }
@@ -1605,6 +1608,10 @@ int sqlite3BtreeOpen(
   }
   p->inTrans = TRANS_NONE;
   p->db = db;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  p->lock.pBtree = p;
+  p->lock.iTable = 1;
+#endif
 
 #if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
   /*
@@ -2376,6 +2383,13 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
   }
 #endif
 
+  /* Any read-only or read-write transaction implies a read-lock on 
+  ** page 1. So if some other shared-cache client already has a write-lock 
+  ** on page 1, the transaction cannot be opened. */
+  if( SQLITE_OK!=(rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK)) ){
+    goto trans_begun;
+  }
+
   do {
     /* Call lockBtree() until either pBt->pPage1 is populated or
     ** lockBtree() returns something other than SQLITE_OK. lockBtree()
@@ -2406,6 +2420,14 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
   if( rc==SQLITE_OK ){
     if( p->inTrans==TRANS_NONE ){
       pBt->nTransaction++;
+#ifndef SQLITE_OMIT_SHARED_CACHE
+      if( p->sharable ){
+	assert( p->lock.pBtree==p && p->lock.iTable==1 );
+        p->lock.eLock = READ_LOCK;
+        p->lock.pNext = pBt->pLock;
+        pBt->pLock = &p->lock;
+      }
+#endif
     }
     p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
     if( p->inTrans>pBt->inTransaction ){
@@ -3188,17 +3210,11 @@ static int btreeCursor(
   assert( sqlite3BtreeHoldsMutex(p) );
   assert( wrFlag==0 || wrFlag==1 );
 
-  /* The following assert statements verify that if this is a sharable b-tree
+  /* The following assert statements verify that if this is a sharable 
-  ** database, the connection is holding the required table locks, and that
+  ** b-tree database, the connection is holding the required table locks, 
-  ** no other connection has any open cursor that conflicts with this lock.
+  ** and that no other connection has any open cursor that conflicts with 
-  **
+  ** this lock.  */
-  ** The exception to this is read-only cursors open on the schema table.
+  assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, wrFlag+1) );
-  ** Such a cursor is opened without a lock while reading the database
-  ** schema. This is safe because BtShared.mutex is held for the entire
-  ** lifetime of this cursor.  */
-  assert( (iTable==1 && wrFlag==0) 
-       || hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, wrFlag+1) 
-  );
   assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
 
   if( NEVER(wrFlag && pBt->readOnly) ){
@@ -6663,10 +6679,7 @@ static int btreeCreateTable(Btree *p, int *piTable, int flags){
     ** root page of the new table should go. meta[3] is the largest root-page
     ** created so far, so the new root-page is (meta[3]+1).
     */
-    rc = sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
+    sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
     pgnoRoot++;
 
     /* The new root-page may not be allocated on a pointer-map page, or the
@@ -6901,11 +6914,7 @@ static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
 #else
     if( pBt->autoVacuum ){
       Pgno maxRootPgno;
-      rc = sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
+      sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
-      if( rc!=SQLITE_OK ){
-        releasePage(pPage);
-        return rc;
-      }
 
       if( iTable==maxRootPgno ){
         /* If the table being dropped is the table with the largest root-page
@@ -6981,6 +6990,9 @@ int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
 
 
 /*
+** This function may only be called if the b-tree connection already
+** has a read or write transaction open on the database.
+**
 ** Read the meta-information out of a database file.  Meta[0]
 ** is the number of free pages currently in the database.  Meta[1]
 ** through meta[15] are available for use by higher layers.  Meta[0]
@@ -6990,71 +7002,24 @@ int sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
 ** layer (and the SetCookie and ReadCookie opcodes) the number of
 ** free pages is not visible.  So Cookie[0] is the same as Meta[1].
 */
-int sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
+void sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
-  DbPage *pDbPage = 0;
-  int rc;
-  unsigned char *pP1;
   BtShared *pBt = p->pBt;
 
   sqlite3BtreeEnter(p);
-
+  assert( p->inTrans>TRANS_NONE );
-  /* Reading a meta-data value requires a read-lock on page 1 (and hence
+  assert( SQLITE_OK==querySharedCacheTableLock(p, 1, READ_LOCK) );
-  ** the sqlite_master table. We grab this lock regardless of whether or
+  assert( pBt->pPage1 );
-  ** not the SQLITE_ReadUncommitted flag is set (the table rooted at page
-  ** 1 is treated as a special case by querySharedCacheTableLock()
-  ** and setSharedCacheTableLock()).
-  */
-  rc = querySharedCacheTableLock(p, 1, READ_LOCK);
-  if( rc!=SQLITE_OK ){
-    sqlite3BtreeLeave(p);
-    return rc;
-  }
-
   assert( idx>=0 && idx<=15 );
-  if( pBt->pPage1 ){
-    /* The b-tree is already holding a reference to page 1 of the database
-    ** file. In this case the required meta-data value can be read directly
-    ** from the page data of this reference. This is slightly faster than
-    ** requesting a new reference from the pager layer.
-    */
-    pP1 = (unsigned char *)pBt->pPage1->aData;
-  }else{
-    /* The b-tree does not have a reference to page 1 of the database file.
-    ** Obtain one from the pager layer.
-    */
-    rc = sqlite3PagerGet(pBt->pPager, 1, &pDbPage);
-    if( rc ){
-      sqlite3BtreeLeave(p);
-      return rc;
-    }
-    pP1 = (unsigned char *)sqlite3PagerGetData(pDbPage);
-  }
-  *pMeta = get4byte(&pP1[36 + idx*4]);
 
-  /* If the b-tree is not holding a reference to page 1, then one was 
+  *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
-  ** requested from the pager layer in the above block. Release it now.
-  */
-  if( !pBt->pPage1 ){
-    sqlite3PagerUnref(pDbPage);
-  }
 
-  /* If autovacuumed is disabled in this build but we are trying to 
+  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
-  ** access an autovacuumed database, then make the database readonly. 
+  ** database, mark the database as read-only.  */
-  */
 #ifdef SQLITE_OMIT_AUTOVACUUM
   if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ) pBt->readOnly = 1;
 #endif
 
-  /* If there is currently an open transaction, grab a read-lock 
-  ** on page 1 of the database file. This is done to make sure that
-  ** no other connection can modify the meta value just read from
-  ** the database until the transaction is concluded.
-  */
-  if( p->inTrans>0 ){
-    rc = setSharedCacheTableLock(p, 1, READ_LOCK);
-  }
   sqlite3BtreeLeave(p);
-  return rc;
 }
 
 /*
@@ -7740,10 +7705,12 @@ int sqlite3BtreeSchemaLocked(Btree *p){
 */
 int sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
   int rc = SQLITE_OK;
+  assert( p->inTrans!=TRANS_NONE );
   if( p->sharable ){
     u8 lockType = READ_LOCK + isWriteLock;
     assert( READ_LOCK+1==WRITE_LOCK );
     assert( isWriteLock==0 || isWriteLock==1 );
+
     sqlite3BtreeEnter(p);
     rc = querySharedCacheTableLock(p, iTab, lockType);
     if( rc==SQLITE_OK ){

src/btree.h

@@ -13,7 +13,7 @@
 ** subsystem.  See comments in the source code for a detailed description
 ** of what each interface routine does.
 **
-** @(#) $Id: btree.h,v 1.116 2009/06/03 11:25:07 danielk1977 Exp $
+** @(#) $Id: btree.h,v 1.117 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #ifndef _BTREE_H_
 #define _BTREE_H_
@@ -97,8 +97,8 @@ int sqlite3BtreeIsInTrans(Btree*);
 int sqlite3BtreeIsInReadTrans(Btree*);
 int sqlite3BtreeIsInBackup(Btree*);
 void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
-int sqlite3BtreeSchemaLocked(Btree *);
+int sqlite3BtreeSchemaLocked(Btree *pBtree);
-int sqlite3BtreeLockTable(Btree *, int, u8);
+int sqlite3BtreeLockTable(Btree *pBtree, int iTab, u8 isWriteLock);
 int sqlite3BtreeSavepoint(Btree *, int, int);
 
 const char *sqlite3BtreeGetFilename(Btree *);
@@ -118,7 +118,7 @@ int sqlite3BtreeDropTable(Btree*, int, int*);
 int sqlite3BtreeClearTable(Btree*, int, int*);
 void sqlite3BtreeTripAllCursors(Btree*, int);
 
-int sqlite3BtreeGetMeta(Btree*, int idx, u32 *pValue);
+void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
 int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);
 
 /*

src/btreeInt.h

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btreeInt.h,v 1.49 2009/06/24 05:40:34 danielk1977 Exp $
+** $Id: btreeInt.h,v 1.50 2009/07/02 07:47:33 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -302,6 +302,24 @@ struct MemPage {
 */
 #define EXTRA_SIZE sizeof(MemPage)
 
+/*
+** A linked list of the following structures is stored at BtShared.pLock.
+** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
+** is opened on the table with root page BtShared.iTable. Locks are removed
+** from this list when a transaction is committed or rolled back, or when
+** a btree handle is closed.
+*/
+struct BtLock {
+  Btree *pBtree;        /* Btree handle holding this lock */
+  Pgno iTable;          /* Root page of table */
+  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
+  BtLock *pNext;        /* Next in BtShared.pLock list */
+};
+
+/* Candidate values for BtLock.eLock */
+#define READ_LOCK     1
+#define WRITE_LOCK    2
+
 /* A Btree handle
 **
 ** A database connection contains a pointer to an instance of
@@ -333,6 +351,9 @@ struct Btree {
   int nBackup;       /* Number of backup operations reading this btree */
   Btree *pNext;      /* List of other sharable Btrees from the same db */
   Btree *pPrev;      /* Back pointer of the same list */
+#ifndef SQLITE_OMIT_SHARED_CACHE
+  BtLock lock;       /* Object used to lock page 1 */
+#endif
 };
 
 /*
@@ -516,24 +537,6 @@ struct BtCursor {
 */
 # define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt)
 
-/*
-** A linked list of the following structures is stored at BtShared.pLock.
-** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
-** is opened on the table with root page BtShared.iTable. Locks are removed
-** from this list when a transaction is committed or rolled back, or when
-** a btree handle is closed.
-*/
-struct BtLock {
-  Btree *pBtree;        /* Btree handle holding this lock */
-  Pgno iTable;          /* Root page of table */
-  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
-  BtLock *pNext;        /* Next in BtShared.pLock list */
-};
-
-/* Candidate values for BtLock.eLock */
-#define READ_LOCK     1
-#define WRITE_LOCK    2
-
 /*
 ** These macros define the location of the pointer-map entry for a 
 ** database page. The first argument to each is the number of usable

src/pragma.c

@@ -11,7 +11,7 @@
 *************************************************************************
 ** This file contains code used to implement the PRAGMA command.
 **
-** $Id: pragma.c,v 1.213 2009/06/19 14:06:03 drh Exp $
+** $Id: pragma.c,v 1.214 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -318,12 +318,13 @@ void sqlite3Pragma(
   */
   if( sqlite3StrICmp(zLeft,"default_cache_size")==0 ){
     static const VdbeOpList getCacheSize[] = {
-      { OP_ReadCookie,  0, 1,        BTREE_DEFAULT_CACHE_SIZE},  /* 0 */
+      { OP_Transaction, 0, 0,        0},                         /* 0 */
-      { OP_IfPos,       1, 6,        0},
+      { OP_ReadCookie,  0, 1,        BTREE_DEFAULT_CACHE_SIZE},  /* 1 */
+      { OP_IfPos,       1, 7,        0},
       { OP_Integer,     0, 2,        0},
       { OP_Subtract,    1, 2,        1},
-      { OP_IfPos,       1, 6,        0},
+      { OP_IfPos,       1, 7,        0},
-      { OP_Integer,     0, 1,        0},  /* 5 */
+      { OP_Integer,     0, 1,        0},                         /* 6 */
       { OP_ResultRow,   1, 1,        0},
     };
     int addr;
@@ -335,7 +336,8 @@ void sqlite3Pragma(
       pParse->nMem += 2;
       addr = sqlite3VdbeAddOpList(v, ArraySize(getCacheSize), getCacheSize);
       sqlite3VdbeChangeP1(v, addr, iDb);
-      sqlite3VdbeChangeP1(v, addr+5, SQLITE_DEFAULT_CACHE_SIZE);
+      sqlite3VdbeChangeP1(v, addr+1, iDb);
+      sqlite3VdbeChangeP1(v, addr+6, SQLITE_DEFAULT_CACHE_SIZE);
     }else{
       int size = atoi(zRight);
       if( size<0 ) size = -size;
@@ -1302,12 +1304,14 @@ void sqlite3Pragma(
     }else{
       /* Read the specified cookie value */
       static const VdbeOpList readCookie[] = {
-        { OP_ReadCookie,      0,  1,  0},    /* 0 */
+        { OP_Transaction,     0,  0,  0},    /* 0 */
+        { OP_ReadCookie,      0,  1,  0},    /* 1 */
         { OP_ResultRow,       1,  1,  0}
       };
       int addr = sqlite3VdbeAddOpList(v, ArraySize(readCookie), readCookie);
       sqlite3VdbeChangeP1(v, addr, iDb);
-      sqlite3VdbeChangeP3(v, addr, iCookie);
+      sqlite3VdbeChangeP1(v, addr+1, iDb);
+      sqlite3VdbeChangeP3(v, addr+1, iCookie);
       sqlite3VdbeSetNumCols(v, 1);
       sqlite3VdbeSetColName(v, 0, COLNAME_NAME, zLeft, SQLITE_TRANSIENT);
     }

src/prepare.c

@@ -13,7 +13,7 @@
 ** interface, and routines that contribute to loading the database schema
 ** from disk.
 **
-** $Id: prepare.c,v 1.125 2009/06/25 11:50:21 drh Exp $
+** $Id: prepare.c,v 1.126 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 
@@ -128,7 +128,6 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
 static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
   int rc;
   int i;
-  BtCursor *curMain;
   int size;
   Table *pTab;
   Db *pDb;
@@ -137,6 +136,7 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
   InitData initData;
   char const *zMasterSchema;
   char const *zMasterName = SCHEMA_TABLE(iDb);
+  int openedTransaction;
 
   /*
   ** The master database table has a structure like this
@@ -210,14 +210,21 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
     }
     return SQLITE_OK;
   }
-  curMain = sqlite3MallocZero(sqlite3BtreeCursorSize());
+
-  if( !curMain ){
+  /* If there is not already a read-only (or read-write) transaction opened
-    rc = SQLITE_NOMEM;
+  ** on the b-tree database, open one now. If a transaction is opened, it 
-    goto error_out;
+  ** will be closed before this function returns.  */
-  }
   sqlite3BtreeEnter(pDb->pBt);
-  rc = sqlite3BtreeCursor(pDb->pBt, MASTER_ROOT, 0, 0, curMain);
+  if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
-  if( rc==SQLITE_EMPTY ) rc = SQLITE_OK;
+    rc = sqlite3BtreeBeginTrans(pDb->pBt, 0);
+    if( rc!=SQLITE_OK ){
+      sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));
+      goto initone_error_out;
+    }
+    openedTransaction = 1;
+  }else{
+    openedTransaction = 0;
+  }
 
   /* Get the database meta information.
   **
@@ -236,12 +243,8 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
   ** Note: The #defined SQLITE_UTF* symbols in sqliteInt.h correspond to
   ** the possible values of meta[4].
   */
-  for(i=0; rc==SQLITE_OK && i<ArraySize(meta); i++){
+  for(i=0; i<ArraySize(meta); i++){
-    rc = sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
+    sqlite3BtreeGetMeta(pDb->pBt, i+1, (u32 *)&meta[i]);
-  }
-  if( rc ){
-    sqlite3SetString(pzErrMsg, db, "%s", sqlite3ErrStr(rc));
-    goto initone_error_out;
   }
   pDb->pSchema->schema_cookie = meta[BTREE_SCHEMA_VERSION-1];
 
@@ -356,8 +359,9 @@ static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
   ** before that point, jump to error_out.
   */
 initone_error_out:
-  sqlite3BtreeCloseCursor(curMain);
+  if( openedTransaction ){
-  sqlite3_free(curMain);
+    sqlite3BtreeCommit(pDb->pBt);
+  }
   sqlite3BtreeLeave(pDb->pBt);
 
 error_out:
@@ -437,13 +441,46 @@ int sqlite3ReadSchema(Parse *pParse){
 ** Check schema cookies in all databases.  If any cookie is out
 ** of date, return 0.  If all schema cookies are current, return 1.
 */
-static int schemaIsValid(sqlite3 *db){
+static void schemaIsValid(Parse *pParse){
+  sqlite3 *db = pParse->db;
   int iDb;
   int rc;
-  BtCursor *curTemp;
   int cookie;
-  int allOk = 1;
 
+  assert( pParse->checkSchema );
+  assert( sqlite3_mutex_held(db->mutex) );
+  for(iDb=0; iDb<db->nDb; iDb++){
+    int openedTransaction = 0;         /* True if a transaction is opened */
+    Btree *pBt = db->aDb[iDb].pBt;     /* Btree database to read cookie from */
+    if( pBt==0 ) continue;
+
+    /* If there is not already a read-only (or read-write) transaction opened
+    ** on the b-tree database, open one now. If a transaction is opened, it 
+    ** will be closed immediately after reading the meta-value. */
+    if( !sqlite3BtreeIsInReadTrans(pBt) ){
+      rc = sqlite3BtreeBeginTrans(pBt, 0);
+      if( NEVER(rc==SQLITE_NOMEM) || rc==SQLITE_IOERR_NOMEM ){
+        db->mallocFailed = 1;
+      }
+      if( rc!=SQLITE_OK ) return;
+      openedTransaction = 1;
+    }
+
+    /* Read the schema cookie from the database. If it does not match the 
+    ** value stored as part of the in the in-memory schema representation,
+    ** set Parse.rc to SQLITE_SCHEMA. */
+    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&cookie);
+    if( cookie!=db->aDb[iDb].pSchema->schema_cookie ){
+      pParse->rc = SQLITE_SCHEMA;
+    }
+
+    /* Close the transaction, if one was opened. */
+    if( openedTransaction ){
+      sqlite3BtreeCommit(pBt);
+    }
+  }
+
+#if 0
   curTemp = (BtCursor *)sqlite3Malloc(sqlite3BtreeCursorSize());
   if( curTemp ){
     assert( sqlite3_mutex_held(db->mutex) );
@@ -470,8 +507,8 @@ static int schemaIsValid(sqlite3 *db){
     allOk = 0;
     db->mallocFailed = 1;
   }
-
   return allOk;
+#endif
 }
 
 /*
@@ -604,8 +641,8 @@ static int sqlite3Prepare(
     pParse->rc = SQLITE_NOMEM;
   }
   if( pParse->rc==SQLITE_DONE ) pParse->rc = SQLITE_OK;
-  if( pParse->checkSchema && !schemaIsValid(db) ){
+  if( pParse->checkSchema ){
-    pParse->rc = SQLITE_SCHEMA;
+    schemaIsValid(pParse);
   }
   if( pParse->rc==SQLITE_SCHEMA ){
     sqlite3ResetInternalSchema(db, 0);

src/test3.c

@@ -13,7 +13,7 @@
 ** is not included in the SQLite library.  It is used for automated
 ** testing of the SQLite library.
 **
-** $Id: test3.c,v 1.105 2009/06/29 06:00:37 danielk1977 Exp $
+** $Id: test3.c,v 1.106 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "btreeInt.h"
@@ -425,12 +425,8 @@ static int btree_get_meta(
     char zBuf[30];
     u32 v;
     sqlite3BtreeEnter(pBt);
-    rc = sqlite3BtreeGetMeta(pBt, i, &v);
+    sqlite3BtreeGetMeta(pBt, i, &v);
     sqlite3BtreeLeave(pBt);
-    if( rc!=SQLITE_OK ){
-      Tcl_AppendResult(interp, errorName(rc), 0);
-      return TCL_ERROR;
-    }
     sqlite3_snprintf(sizeof(zBuf), zBuf,"%d",v);
     Tcl_AppendElement(interp, zBuf);
   }

src/vacuum.c

@@ -14,7 +14,7 @@
 ** Most of the code in this file may be omitted by defining the
 ** SQLITE_OMIT_VACUUM macro.
 **
-** $Id: vacuum.c,v 1.90 2009/06/03 11:25:07 danielk1977 Exp $
+** $Id: vacuum.c,v 1.91 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -254,8 +254,7 @@ int sqlite3RunVacuum(char **pzErrMsg, sqlite3 *db){
     for(i=0; i<ArraySize(aCopy); i+=2){
       /* GetMeta() and UpdateMeta() cannot fail in this context because
       ** we already have page 1 loaded into cache and marked dirty. */
-      rc = sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
+      sqlite3BtreeGetMeta(pMain, aCopy[i], &meta);
-      if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
       rc = sqlite3BtreeUpdateMeta(pTemp, aCopy[i], meta+aCopy[i+1]);
       if( NEVER(rc!=SQLITE_OK) ) goto end_of_vacuum;
     }

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 1.867 2009/06/29 06:00:37 danielk1977 Exp $
+** $Id: vdbe.c,v 1.868 2009/07/02 07:47:33 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -2759,7 +2759,7 @@ case OP_ReadCookie: {               /* out2-prerelease */
   assert( db->aDb[iDb].pBt!=0 );
   assert( (p->btreeMask & (1<<iDb))!=0 );
 
-  rc = sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);
+  sqlite3BtreeGetMeta(db->aDb[iDb].pBt, iCookie, (u32 *)&iMeta);
   pOut->u.i = iMeta;
   MemSetTypeFlag(pOut, MEM_Int);
   break;
@@ -2824,12 +2824,11 @@ case OP_VerifyCookie: {
   assert( (p->btreeMask & (1<<pOp->p1))!=0 );
   pBt = db->aDb[pOp->p1].pBt;
   if( pBt ){
-    rc = sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&iMeta);
+    sqlite3BtreeGetMeta(pBt, BTREE_SCHEMA_VERSION, (u32 *)&iMeta);
   }else{
-    rc = SQLITE_OK;
     iMeta = 0;
   }
-  if( rc==SQLITE_OK && iMeta!=pOp->p2 ){
+  if( iMeta!=pOp->p2 ){
     sqlite3DbFree(db, p->zErrMsg);
     p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
     /* If the schema-cookie from the database file matches the cookie 

src/vdbeblob.c

@@ -12,7 +12,7 @@
 **
 ** This file contains code used to implement incremental BLOB I/O.
 **
-** $Id: vdbeblob.c,v 1.34 2009/06/29 06:00:37 danielk1977 Exp $
+** $Id: vdbeblob.c,v 1.35 2009/07/02 07:47:33 danielk1977 Exp $
 */
 
 #include "sqliteInt.h"