Add evidence marks and assert()s used as evidence for checkpoint requirements.

FossilOrigin-Name: b2da8afc7657266fbe8e683c6e50fe18216cbcf3

manifest

@@ -1,5 +1,5 @@
-C Fix\sover-length\scomment\slines\sin\ssqlite.h.in.\s\sNo\schanges\sto\scode.
+C Add\sevidence\smarks\sand\sassert()s\sused\sas\sevidence\sfor\scheckpoint\srequirements.
-D 2014-12-03T19:08:00.822
+D 2014-12-03T19:25:41.425
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in a226317fdf3f4c895fb3cfedc355b4d0868ce1fb
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -216,7 +216,7 @@ F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
 F src/os_unix.c fb587121840f690101336879adfa6d0b2cd0e8c7
 F src/os_win.c a9e500dd963fb1f67d7860e58b5772abe6123862
 F src/os_win.h 09e751b20bbc107ffbd46e13555dc73576d88e21
-F src/pager.c b8764f90c135482988268eec93d7f5cdb89d687a
+F src/pager.c 7a5c5bc0e29b9b16834f5558a9d5d22bbae59a08
 F src/pager.h d1eee3c3f741be247ce6d82752a178515fc8578b
 F src/parse.y 5dfead8aed90cb0c7c1115898ee2266804daff45
 F src/pcache.c ace1b67632deeaa84859b4c16c27711dfb7db3d4
@@ -301,7 +301,7 @@ F src/vdbemem.c 31d8eabb0cd78bfeab4e5124c7363c3e9e54db9f
 F src/vdbesort.c 42c166f7ca78cb643c7f4e4bdfa83c59d363d1a6
 F src/vdbetrace.c 7e4222955e07dd707a2f360c0eb73452be1cb010
 F src/vtab.c c08ec66f45919eaa726bf88aa53eb08379d607f9
-F src/wal.c e396f31038aa01b9de95584b703692716275aedc
+F src/wal.c fc62ec9dc7dfa08dbe08801332230cf28130a159
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c c253b95b4ee44b21c406e2a1052636c31ea27804
 F src/where.c a0b16f9d78321cb340a977287d19f826555c7d3b
@@ -1223,7 +1223,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 026c44ff2c092b14faa19985dd46873aeb8727dc
+P cbd357fd8c25c9c6043063710a3e2a89ff8b4575
-R 4ed5b70763e0743b0e322aa2df0b85da
+R bf75abced12e09ba377b1add0a3ea61a
 U drh
-Z 6507e8b7c8c2131b9414f714dc2b9292
+Z 0545aa7eaccc2c8413582324bb7aef19

manifest.uuid

@@ -1 +1 @@
-cbd357fd8c25c9c6043063710a3e2a89ff8b4575
+b2da8afc7657266fbe8e683c6e50fe18216cbcf3

src/pager.c

@@ -7075,7 +7075,8 @@ int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
   int rc = SQLITE_OK;
   if( pPager->pWal ){
     rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
-        pPager->xBusyHandler, pPager->pBusyHandlerArg,
+        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
+        pPager->pBusyHandlerArg,
         pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
         pnLog, pnCkpt
     );

src/wal.c

@@ -1689,7 +1689,7 @@ static void walRestartHdr(Wal *pWal, u32 salt1){
 static int walCheckpoint(
   Wal *pWal,                      /* Wal connection */
   int eMode,                      /* One of PASSIVE, FULL or RESTART */
-  int (*xBusyCall)(void*),        /* Function to call when busy */
+  int (*xBusy)(void*),            /* Function to call when busy */
   void *pBusyArg,                 /* Context argument for xBusyHandler */
   int sync_flags,                 /* Flags for OsSync() (or 0) */
   u8 *zBuf                        /* Temporary buffer to use */
@@ -1703,7 +1703,6 @@ static int walCheckpoint(
   u32 mxPage;                     /* Max database page to write */
   int i;                          /* Loop counter */
   volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
-  int (*xBusy)(void*) = 0;        /* Function to call when waiting for locks */
 
   szPage = walPagesize(pWal);
   testcase( szPage<=32768 );
@@ -1718,7 +1717,9 @@ static int walCheckpoint(
   }
   assert( pIter );
 
-  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ) xBusy = xBusyCall;
+  /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
+  ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
+  assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
 
   /* Compute in mxSafeFrame the index of the last frame of the WAL that is
   ** safe to write into the database.  Frames beyond mxSafeFrame might
@@ -2943,7 +2944,7 @@ int sqlite3WalFrames(
 */
 int sqlite3WalCheckpoint(
   Wal *pWal,                      /* Wal connection */
-  int eMode,                      /* PASSIVE, FULL or RESTART */
+  int eMode,                      /* PASSIVE, FULL, RESTART, or TRUNCATE */
   int (*xBusy)(void*),            /* Function to call when busy */
   void *pBusyArg,                 /* Context argument for xBusyHandler */
   int sync_flags,                 /* Flags to sync db file with (or 0) */
@@ -2955,29 +2956,42 @@ int sqlite3WalCheckpoint(
   int rc;                         /* Return code */
   int isChanged = 0;              /* True if a new wal-index header is loaded */
   int eMode2 = eMode;             /* Mode to pass to walCheckpoint() */
+  int (*xBusy2)(void*) = xBusy;   /* Busy handler for eMode2 */
 
   assert( pWal->ckptLock==0 );
   assert( pWal->writeLock==0 );
 
+  /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
+  ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
+  assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
+
   if( pWal->readOnly ) return SQLITE_READONLY;
   WALTRACE(("WAL%p: checkpoint begins\n", pWal));
+
+  /* IMPLEMENTATION-OF: R-62028-47212 All calls obtain an exclusive 
+  ** "checkpoint" lock on the database file. */
   rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1);
   if( rc ){
-    /* Usually this is SQLITE_BUSY meaning that another thread or process
+    /* EVIDENCE-OF: R-10421-19736 If any other process is running a
-    ** is already running a checkpoint, or maybe a recovery.  But it might
+    ** checkpoint operation at the same time, the lock cannot be obtained and
-    ** also be SQLITE_IOERR. */
+    ** SQLITE_BUSY is returned.
+    ** EVIDENCE-OF: R-53820-33897 Even if there is a busy-handler configured,
+    ** it will not be invoked in this case.
+    */
+    testcase( rc==SQLITE_BUSY );
+    testcase( xBusy!=0 );
     return rc;
   }
   pWal->ckptLock = 1;
 
-  /* If this is a blocking-checkpoint, then obtain the write-lock as well
+  /* IMPLEMENTATION-OF: R-59782-36818 The SQLITE_CHECKPOINT_FULL, RESTART and
-  ** to prevent any writers from running while the checkpoint is underway.
+  ** TRUNCATE modes also obtain the exclusive "writer" lock on the database
-  ** This has to be done before the call to walIndexReadHdr() below.
+  ** file.
   **
-  ** If the writer lock cannot be obtained, then a passive checkpoint is
+  ** EVIDENCE-OF: R-60642-04082 If the writer lock cannot be obtained
-  ** run instead. Since the checkpointer is not holding the writer lock,
+  ** immediately, and a busy-handler is configured, it is invoked and the
-  ** there is no point in blocking waiting for any readers. Assuming no 
+  ** writer lock retried until either the busy-handler returns 0 or the
-  ** other error occurs, this function will return SQLITE_BUSY to the caller.
+  ** lock is successfully obtained.
   */
   if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
     rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_WRITE_LOCK, 1);
@@ -2985,6 +2999,7 @@ int sqlite3WalCheckpoint(
       pWal->writeLock = 1;
     }else if( rc==SQLITE_BUSY ){
       eMode2 = SQLITE_CHECKPOINT_PASSIVE;
+      xBusy2 = 0;
       rc = SQLITE_OK;
     }
   }
@@ -3002,7 +3017,7 @@ int sqlite3WalCheckpoint(
     if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
       rc = SQLITE_CORRUPT_BKPT;
     }else{
-      rc = walCheckpoint(pWal, eMode2, xBusy, pBusyArg, sync_flags, zBuf);
+      rc = walCheckpoint(pWal, eMode2, xBusy2, pBusyArg, sync_flags, zBuf);
     }
 
     /* If no error occurred, set the output variables. */