Correction to check-ins (6246) and (6247): The backup object might not

hold a valid destination connection pointer.  Also, do not reset the
page cache when establishing a read-lock while there is a persistent
or truncated journal, only if there is a journal that really needs to
rollback.  Otherwise backups always reset whenever the source database
file is read. (CVS 6248)

FossilOrigin-Name: 7f827ba9d7af2dfe44aed386b4407716c85daf5e

manifest

@@ -1,5 +1,5 @@
-C A\sbackup\smust\sclear\sthe\sinternal\sschema\sof\sthe\sdestination\sdatabase\sso\nthat\sthe\sschema\swill\sbe\sreloaded\sfor\sthe\snext\ssqlite3_prepare()\s(CVS\s6247)
+C Correction\sto\scheck-ins\s(6246)\sand\s(6247):\s\sThe\sbackup\sobject\smight\snot\nhold\sa\svalid\sdestination\sconnection\spointer.\s\sAlso,\sdo\snot\sreset\sthe\npage\scache\swhen\sestablishing\sa\sread-lock\swhile\sthere\sis\sa\spersistent\nor\struncated\sjournal,\sonly\sif\sthere\sis\sa\sjournal\sthat\sreally\sneeds\sto\nrollback.\s\sOtherwise\sbackups\salways\sreset\swhenever\sthe\ssource\sdatabase\nfile\sis\sread.\s(CVS\s6248)
-D 2009-02-03T22:17:42
+D 2009-02-03T22:51:06
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in c7a5a30fb6852bd7839b1024e1661da8549878ee
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -101,7 +101,7 @@ F src/alter.c 0ec29744c36c6e976596ce38c16289ebc5dc94db
 F src/analyze.c c86fd6a1425b22b3a46ce72ad403e4280026364f
 F src/attach.c 81d37d1948f409146a7b22b96998fd90649d1fd3
 F src/auth.c c8b2ab5c8bad4bd90ed7c294694f48269162c627
-F src/backup.c 0491573a4ce3bb8cfb5c6da32f0d42d04b79407a
+F src/backup.c ddae8526793b0e2fab7d9e686b63c766218dfabe
 F src/bitvec.c 44f7059ac1f874d364b34af31b9617e52223ba75
 F src/btmutex.c 63c5cc4ad5715690767ffcb741e185d7bc35ec1a
 F src/btree.c 800a065686c49a0cdefc933779a750a7c3c0509f
@@ -143,7 +143,7 @@ F src/os_common.h 24525d8b7bce66c374dfc1810a6c9043f3359b60
 F src/os_os2.c bed77dc26e3a95ce4a204936b9a1ca6fe612fcc5
 F src/os_unix.c f0fce3042011d462b8ae633564a5668260bd3636
 F src/os_win.c ec133f2a3c0da786995ea09ba67056af8f18cc2e
-F src/pager.c 9e7c6db1635be2caf31ff3d407ecb2e145f89a8a
+F src/pager.c b8f4ae64cb179618da4bc08989c7bd5a50a5e12a
 F src/pager.h 0c9f3520c00d8a3b8e792ca56c9a11b6b02b4b0f
 F src/parse.y 4f4d16aee0d11f69fec2adb77dac88878043ed8d
 F src/pcache.c fcf7738c83c4d3e9d45836b2334c8a368cc41274
@@ -700,7 +700,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
 F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
-P 5f6c06b974f26532264467ace603b6f1f830fba9
+P 76f23a4394574e31f237e55c641bc70534f44d97
-R 56f7689073a568269b1239d4961d1fb6
+R 5bdad9729a46d9221b6bdee25bf60220
 U drh
-Z b3307c22d24e3af571a952d745c2e4d1
+Z a3b0a3e20a12c71211622ecafa1dae99

manifest.uuid

@@ -1 +1 @@
-76f23a4394574e31f237e55c641bc70534f44d97
+7f827ba9d7af2dfe44aed386b4407716c85daf5e

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 1.3 2009/02/03 22:17:42 drh Exp $
+** $Id: backup.c,v 1.4 2009/02/03 22:51:06 drh Exp $
 */
 #include "sqliteInt.h"
 #include "btreeInt.h"
@@ -251,7 +251,9 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
 
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
+  if( p->pDestDb ){
     sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
 
   rc = p->rc;
   if( rc==SQLITE_OK ){
@@ -324,7 +326,9 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
       ** same schema version.
       */
       sqlite3BtreeUpdateMeta(p->pDest, 1, p->iDestSchema+1);
+      if( p->pDestDb ){
         sqlite3ResetInternalSchema(p->pDestDb, 0);
+      }
 
       /* Set nDestTruncate to the final number of pages in the destination
       ** database. The complication here is that the destination page
@@ -408,7 +412,9 @@ int sqlite3_backup_step(sqlite3_backup *p, int nPage){
       p->rc = rc;
     }
   }
+  if( p->pDestDb ){
     sqlite3_mutex_leave(p->pDestDb->mutex);
+  }
   sqlite3BtreeLeave(p->pSrc);
   sqlite3_mutex_leave(p->pSrcDb->mutex);
   return rc;
@@ -426,7 +432,9 @@ int sqlite3_backup_finish(sqlite3_backup *p){
   sqlite3_mutex_enter(p->pSrcDb->mutex);
   sqlite3BtreeEnter(p->pSrc);
   mutex = p->pSrcDb->mutex;
+  if( p->pDestDb ){
     sqlite3_mutex_enter(p->pDestDb->mutex);
+  }
 
   /* Detach this backup from the source pager. */
   if( p->pDestDb ){
@@ -446,7 +454,9 @@ int sqlite3_backup_finish(sqlite3_backup *p){
   sqlite3Error(p->pDestDb, rc, 0);
 
   /* Exit the mutexes and free the backup context structure. */
+  if( p->pDestDb ){
     sqlite3_mutex_leave(p->pDestDb->mutex);
+  }
   sqlite3BtreeLeave(p->pSrc);
   if( p->pDestDb ){
     sqlite3_free(p);

src/pager.c

@@ -18,7 +18,7 @@
 ** file simultaneously, or one process from reading the database while
 ** another is writing.
 **
-** @(#) $Id: pager.c,v 1.562 2009/02/03 16:51:25 danielk1977 Exp $
+** @(#) $Id: pager.c,v 1.563 2009/02/03 22:51:06 drh Exp $
 */
 #ifndef SQLITE_OMIT_DISKIO
 #include "sqliteInt.h"
@@ -1895,6 +1895,13 @@ static void setSectorSize(Pager *pPager){
 **
 ** If an I/O or malloc() error occurs, the journal-file is not deleted
 ** and an error code is returned.
+**
+** The isHot parameter indicates that we are trying to rollback a journal
+** that might be a hot journal.  Or, it could be that the journal is 
+** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
+** If the journal really is hot, reset the pager cache prior rolling
+** back any content.  If the journal is merely persistent, no reset is
+** needed.
 */
 static int pager_playback(Pager *pPager, int isHot){
   sqlite3_vfs *pVfs = pPager->pVfs;
@@ -1905,6 +1912,7 @@ static int pager_playback(Pager *pPager, int isHot){
   int rc;                  /* Result code of a subroutine */
   int res = 1;             /* Value returned by sqlite3OsAccess() */
   char *zMaster = 0;       /* Name of master journal file if any */
+  int needPagerReset;      /* True to reset page prior to first page rollback */
 
   /* Figure out how many records are in the journal.  Abort early if
   ** the journal is empty.
@@ -1936,6 +1944,7 @@ static int pager_playback(Pager *pPager, int isHot){
     goto end_playback;
   }
   pPager->journalOff = 0;
+  needPagerReset = isHot;
 
   /* This loop terminates either when a readJournalHdr() or 
   ** pager_playback_one_page() call returns SQLITE_DONE or an IO error 
@@ -2005,6 +2014,10 @@ static int pager_playback(Pager *pPager, int isHot){
     ** database file and/or page cache.
     */
     for(u=0; u<nRec; u++){
+      if( needPagerReset ){
+        pager_reset(pPager);
+        needPagerReset = 0;
+      }
       rc = pager_playback_one_page(pPager, 1, &pPager->journalOff, 0, 0);
       if( rc!=SQLITE_OK ){
         if( rc==SQLITE_DONE ){
@@ -3557,7 +3570,6 @@ static int pagerSharedLock(Pager *pPager){
       ** playing back the hot-journal so that we don't end up with
       ** an inconsistent cache.
       */
-      pager_reset(pPager);
       rc = pager_playback(pPager, 1);
       if( rc!=SQLITE_OK ){
         rc = pager_error(pPager, rc);