From: dan <dan@noemail.net>
Date: Wed, 21 Apr 2010 11:43:38 +0000 (+0000)
Subject: If, after obtaining a SHARED lock, there exists a *-wal file in the file-system,... 
X-Git-Tag: version-3.7.2~455^2~66
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a470aeb4ac0de99fc8d34d1a4006fbc9ebb402c9;p=thirdparty%2Fsqlite.git

If, after obtaining a SHARED lock, there exists a *-wal file in the file-system, use WAL mode. This is necessary to recover from a crash that damages the first page of the database file.

FossilOrigin-Name: 33cabf271b8f4dda508a610bf59964273fe2cb84
---

diff --git a/manifest b/manifest
index be9552df7d..324d0ff215 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Minor\schanges\sto\stest\scases\sto\saccount\sfor\sthe\sfact\sthat\sdatabases\swith\sread/write\sversions\sof\s2\sare\snow\sunderstood.
-D 2010-04-21T06:19:13
+C If,\safter\sobtaining\sa\sSHARED\slock,\sthere\sexists\sa\s*-wal\sfile\sin\sthe\sfile-system,\suse\sWAL\smode.\sThis\sis\snecessary\sto\srecover\sfrom\sa\scrash\sthat\sdamages\sthe\sfirst\spage\sof\sthe\sdatabase\sfile.
+D 2010-04-21T11:43:38
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in 4f2f967b7e58a35bb74fb7ec8ae90e0f4ca7868b
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -109,7 +109,7 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c e86634da8c48357a759694c9c7c471125cd8d5a8
 F src/bitvec.c 06ad2c36a9c3819c0b9cbffec7b15f58d5d834e0
 F src/btmutex.c 96a12f50f7a17475155971a241d85ec5171573ff
-F src/btree.c 013cf019484e309e909a667654612b38a02dc2b6
+F src/btree.c e6ef1020c35db638f9ebbc91b77bc6493d9be2a1
 F src/btree.h dd83041eda10c17daf023257c1fc883b5f71f85a
 F src/btreeInt.h 22447d259639271774a931cbf66aa55112846681
 F src/build.c 11100b66fb97638d2d874c1d34d8db90650bb1d7
@@ -154,7 +154,7 @@ F src/os_common.h 240c88b163b02c21a9f21f87d49678a0aa21ff30
 F src/os_os2.c 75a8c7b9a00a2cf1a65f9fa4afbc27d46634bb2f
 F src/os_unix.c 5bf0015cebe2f21635da2af983c348eb88b3b4c1
 F src/os_win.c 1c7453c2df4dab26d90ff6f91272aea18bcf7053
-F src/pager.c 1dcf76bead8f1b51809bd8189ef9b02f2c94dc7f
+F src/pager.c 4ff50f4e72ca7fff6c1e40e67db78377a53879fe
 F src/pager.h cee4487ab4f0911dd9f22a40e3cd55afdb7ef444
 F src/parse.y ace5c7a125d9f2a410e431ee3209034105045f7e
 F src/pcache.c ace8f6a5ecd4711cc66a1b23053be7109bd437cf
@@ -758,8 +758,8 @@ F test/vtabE.test 7c4693638d7797ce2eda17af74292b97e705cc61
 F test/vtab_alter.test 9e374885248f69e251bdaacf480b04a197f125e5
 F test/vtab_err.test 0d4d8eb4def1d053ac7c5050df3024fd47a3fbd8
 F test/vtab_shared.test 0eff9ce4f19facbe0a3e693f6c14b80711a4222d
-F test/wal.test 273c0006e75c99cb34d0659851e7103fd4748c20
-F test/walcrash.test 45cfbab30bb7cbe0b2e9d5cabe90dbcad10cb89b
+F test/wal.test 9ee4025785972fa509250c1f20c5b9456472a789
+F test/walcrash.test f022cee7eb7baa5fb898726120a6a4073dd831d1
 F test/walhook.test 76a559e262f0715c470bade4a8d8333035f8ee47
 F test/walmode.test cd6ee20f08af2d81fddc049f8d7e387a807f067e
 F test/walslow.test 38076d5fad49e3678027be0f8110e6a32d531dc2
@@ -807,7 +807,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 96bef18c1411c3e0348295886f105e1646c46320
-R 9d271c34e1ffdb3d856b3b8726b0e8d7
+P 278ed41e1d4bbff9544cb2cf4cf52dbbcf0c17df
+R aeea7589488764dd7471605e974b33ab
 U dan
-Z 58b9eaab75f6eeb69a49f445ee7bfb3c
+Z eeb703c307b6c73f6f34fd39a65a4afd
diff --git a/manifest.uuid b/manifest.uuid
index 3378df2d22..f51f56c3a0 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-278ed41e1d4bbff9544cb2cf4cf52dbbcf0c17df
\ No newline at end of file
+33cabf271b8f4dda508a610bf59964273fe2cb84
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 069c2d0327..2c387ffabf 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -2268,7 +2268,14 @@ static int lockBtree(BtShared *pBt){
       goto page1_init_failed;
     }
 
-    /* If the write version is set to 2, turn on write-ahead logging mode. */
+    /* If the write version is set to 2, this database should be accessed
+    ** in WAL mode. If the log is not already open, open it now. Then 
+    ** return SQLITE_OK and return without populating BtShared.pPage1.
+    ** The caller detects this and calls this function again. This is
+    ** required as the version of page 1 currently in the page1 buffer
+    ** may not be the latest version - there may be a newer one in the log
+    ** file.
+    */
     if( page1[19]==2 ){
       int isOpen = 0;
       rc = sqlite3PagerOpenLog(pBt->pPager, &isOpen);
diff --git a/src/pager.c b/src/pager.c
index 9d1fd0479c..48e67fdb03 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -491,6 +491,16 @@ static int assert_pager_state(Pager *pPager){
 }
 #endif
 
+#ifndef NDEBUG 
+static void assert_file_lock(Pager *pPager, int eLock){
+  int locktype;
+  sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_LOCKSTATE, &locktype);
+  assert( locktype==eLock );
+}
+#else
+# define assert_file_lock(x,y) 
+#endif
+
 
 /*
 ** Return true if it is necessary to write page *pPg into the sub-journal.
@@ -3726,6 +3736,59 @@ static int hasHotJournal(Pager *pPager, int *pExists){
   return rc;
 }
 
+/*
+** Check if the *-wal file that corresponds to the database opened by pPager
+** exists. Assuming no error occurs, set *pExists to 1 if the file exists,
+** or 0 otherwise and return SQLITE_OK. If an IO or OOM error occurs, return
+** an SQLite error code.
+**
+** The caller must hold a SHARED lock on the database file to call this
+** function.
+*/
+static int pagerHasWAL(Pager *pPager, int *pExists){
+  int rc;                         /* Return code */
+
+  /* Check that a SHARED lock is held on the database file. Because an
+  ** EXCLUSIVE lock on the db file is required to delete a WAL, this
+  ** ensures there is no race condition between the xAccess() below and
+  ** an xDelete() being executed by some other connection.
+  */
+  assert_file_lock(pPager, SQLITE_LOCK_SHARED);
+
+  if( !pPager->tempFile ){
+    char *zLog = sqlite3_mprintf("%s-wal", pPager->zFilename);
+    if( !zLog ){
+      rc = SQLITE_NOMEM;
+    }else{
+      rc = sqlite3OsAccess(pPager->pVfs, zLog, SQLITE_ACCESS_EXISTS, pExists);
+      sqlite3_free(zLog);
+    }
+  }else{
+    rc = SQLITE_OK;
+    *pExists = 0;
+  }
+  return rc;
+}
+
+static int pagerOpenSnapshot(Pager *pPager){
+  int rc;
+  int changed;
+
+  assert( pagerUseLog(pPager) );
+
+  rc = sqlite3LogOpenSnapshot(pPager->pLog, &changed);
+  if( rc==SQLITE_OK ){
+    int dummy;
+    if( changed ){
+        pager_reset(pPager);
+        assert( pPager->errCode || pPager->dbSizeValid==0 );
+    }
+    rc = sqlite3PagerPagecount(pPager, &dummy);
+  }
+  pPager->state = PAGER_SHARED;
+
+  return rc;
+}
 
 /*
 ** This function is called to obtain a shared lock on the database file.
@@ -3781,23 +3844,11 @@ int sqlite3PagerSharedLock(Pager *pPager){
   }
 
   if( pagerUseLog(pPager) ){
-    int changed = 0;              /* True if the cache must be flushed */
-
-    /* Open a log snapshot to read from. */
-    rc = sqlite3LogOpenSnapshot(pPager->pLog, &changed);
-    if( rc==SQLITE_OK ){
-      int dummy;
-      if( changed ){
-        pager_reset(pPager);
-        assert( pPager->errCode || pPager->dbSizeValid==0 );
-      }
-      rc = sqlite3PagerPagecount(pPager, &dummy);
-    }
-    pPager->state = PAGER_SHARED;
-
+    rc = pagerOpenSnapshot(pPager);
   }else if( pPager->state==PAGER_UNLOCK || isErrorReset ){
     sqlite3_vfs * const pVfs = pPager->pVfs;
     int isHotJournal = 0;
+    int isWal = 0;
     assert( !MEMDB );
     assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
     if( pPager->noReadlock ){
@@ -3952,7 +4003,17 @@ int sqlite3PagerSharedLock(Pager *pPager){
     }
     assert( pPager->exclusiveMode || pPager->state==PAGER_SHARED );
 
-    if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
+    rc = pagerHasWAL(pPager, &isWal);
+    if( rc!=SQLITE_OK ){
+      goto failed;
+    }
+    if( isWal ){
+      pager_reset(pPager);
+      rc = sqlite3PagerOpenLog(pPager, 0);
+      if( rc==SQLITE_OK ){
+        rc = pagerOpenSnapshot(pPager);
+      }
+    }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
       pPager->journalMode = PAGER_JOURNALMODE_DELETE;
     }
   }
@@ -5675,13 +5736,7 @@ int sqlite3PagerLogCallback(Pager *pPager){
 int sqlite3PagerOpenLog(Pager *pPager, int *pisOpen){
   int rc = SQLITE_OK;             /* Return code */
 
-#ifdef SQLITE_DEBUG
-  int locktype;
-  sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_LOCKSTATE, &locktype);
-  assert( locktype==SQLITE_LOCK_SHARED );
-  assert( pPager->state>=PAGER_SHARED );
-#endif
-
+  assert_file_lock(pPager, SQLITE_LOCK_SHARED);
   if( !pPager->pLog ){
 
     /* Open the connection to the log file. If this operation fails, 
@@ -5725,15 +5780,7 @@ int sqlite3PagerCloseLog(Pager *pPager){
       pPager->pLog = 0;
     }
 
-    /* Make sure the EXCLUSIVE lock has not been lost somehow */
-#ifdef SQLITE_DEBUG
-    {
-      int locktype;
-      sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_LOCKSTATE, &locktype);
-      assert( locktype==SQLITE_LOCK_EXCLUSIVE );
-    }
-#endif
-
+    assert_file_lock(pPager, SQLITE_LOCK_EXCLUSIVE);
   }
   return rc;
 }
diff --git a/test/wal.test b/test/wal.test
index bb538b120f..2c73904634 100644
--- a/test/wal.test
+++ b/test/wal.test
@@ -685,7 +685,6 @@ do_test wal-12.4 {
 } {B 1}
 db2 close
 
-file copy -force test.db-wal A
 do_test wal-12.5 {
   execsql {
     PRAGMA checkpoint;
@@ -697,7 +696,6 @@ do_test wal-12.5 {
     SELECT * FROM t2;
   }
 } {B 2}
-file copy -force test.db-wal B
 
 do_test wal-12.4 {
   file copy -force test.db test2.db
diff --git a/test/walcrash.test b/test/walcrash.test
index dd4c572941..ed2b292861 100644
--- a/test/walcrash.test
+++ b/test/walcrash.test
@@ -32,11 +32,6 @@ db close
 set seed 0
 set REPEATS 100
 
-proc sqlite3_wal {args} {
-  eval sqlite3 $args
-  [lindex $args 0] eval { PRAGMA journal_mode = wal }
-}
-
 # walcrash-1.*
 #
 for {set i 1} {$i < $REPEATS} {incr i} {
@@ -51,7 +46,7 @@ for {set i 1} {$i < $REPEATS} {incr i} {
     }
   } {1 {child process exited abnormally}}
   do_test walcrash-1.$i.2 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT sum(a)==max(b) FROM t1 }
   } {1}
   integrity_check walcrash-1.$i.3
@@ -59,17 +54,18 @@ for {set i 1} {$i < $REPEATS} {incr i} {
   
   do_test walcrash-1.$i.4 {
     crashsql -delay 2 -file test.db-wal -seed [incr seed] {
-      PRAGMA journal_mode = WAL;
-      PRAGMA journal_mode = WAL;
       INSERT INTO t1 VALUES(4, (SELECT sum(a) FROM t1) + 4);
       INSERT INTO t1 VALUES(5, (SELECT sum(a) FROM t1) + 5);
     }
   } {1 {child process exited abnormally}}
   do_test walcrash-1.$i.5 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT sum(a)==max(b) FROM t1 }
   } {1}
   integrity_check walcrash-1.$i.6
+  do_test walcrash-1.$i.5 {
+    execsql { PRAGMA main.journal_mode }
+  } {wal}
   db close
 }
 
@@ -87,7 +83,7 @@ for {set i 1} {$i < $REPEATS} {incr i} {
     }
   } {1 {child process exited abnormally}}
   do_test walcrash-2.$i.2 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT sum(a)==max(b) FROM t1 }
   } {1}
   integrity_check walcrash-2.$i.3
@@ -95,16 +91,18 @@ for {set i 1} {$i < $REPEATS} {incr i} {
   
   do_test walcrash-2.$i.4 {
     crashsql -delay 2 -file test.db-wal -seed [incr seed] {
-      PRAGMA journal_mode = WAL;
       INSERT INTO t1 VALUES(6, (SELECT sum(a) FROM t1) + 6);
       INSERT INTO t1 VALUES(7, (SELECT sum(a) FROM t1) + 7);
     }
   } {1 {child process exited abnormally}}
   do_test walcrash-2.$i.5 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT sum(a)==max(b) FROM t1 }
   } {1}
   integrity_check walcrash-2.$i.6
+  do_test walcrash-2.$i.6 {
+    execsql { PRAGMA main.journal_mode }
+  } {wal}
   db close
 }
 
@@ -157,12 +155,13 @@ for {set i 1} {$i < $REPEATS} {incr i} {
   } {1 {child process exited abnormally}}
 
   do_test walcrash-4.$i.2 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { 
       SELECT * FROM t1 WHERE a = 1;
     }
   } {1 2}
   do_test walcrash-4.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
+  do_test walcrash-4.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}
 
   db close
 }
@@ -199,10 +198,11 @@ for {set i 1} {$i < $REPEATS} {incr i} {
   } {1 {child process exited abnormally}}
 
   do_test walcrash-5.$i.2 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT count(*)==33 OR count(*)==34 FROM t1 WHERE x != 1 }
   } {1}
   do_test walcrash-5.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
+  do_test walcrash-5.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}
 
   db close
 }
@@ -239,10 +239,37 @@ for {set i 1} {$i < $REPEATS} {incr i} {
   } {1 {child process exited abnormally}}
 
   do_test walcrash-6.$i.2 {
-    sqlite3_wal db test.db
+    sqlite3 db test.db
     execsql { SELECT count(*)==34 OR count(*)==35 FROM t1 WHERE x != 1 }
   } {1}
   do_test walcrash-6.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
+  do_test walcrash-6.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}
+
+  db close
+}
+
+for {set i 1} {$i < $REPEATS} {incr i} {
+  file delete -force test.db test.db-wal
+
+  do_test walcrash-7.$i.1 {
+    crashsql -delay 3 -file test.db -seed [incr seed] -blocksize 512 {
+      PRAGMA journal_mode = wal;
+      BEGIN;
+        CREATE TABLE t1(a, b);
+        INSERT INTO t1 VALUES(1, 2);
+      COMMIT;
+      PRAGMA checkpoint;
+      CREATE INDEX i1 ON t1(a);
+      PRAGMA checkpoint;
+    }
+  } {1 {child process exited abnormally}}
+
+  do_test walcrash-7.$i.2 {
+    sqlite3 db test.db
+    execsql { SELECT b FROM t1 WHERE a = 1 }
+  } {2}
+  do_test walcrash-7.$i.3 { execsql { PRAGMA main.integrity_check } } {ok}
+  do_test walcrash-7.$i.4 { execsql { PRAGMA main.journal_mode } } {wal}
 
   db close
 }