Remove entries from wal-index hash tables when a rollback or savepoint rollback occurs.

FossilOrigin-Name: 36795c2b23a78978528cace193e386138adacd41

manifest

@@ -1,8 +1,5 @@
------BEGIN PGP SIGNED MESSAGE-----
+C Remove\sentries\sfrom\swal-index\shash\stables\swhen\sa\srollback\sor\ssavepoint\srollback\soccurs.
-Hash: SHA1
+D 2010-05-21T15:31:57
-
-C Fix\sthe\swal-index\sheader\sread\sroutine\sso\sthat\sit\scorrectly\sdetects\sa\szero\nheader\sas\sbeing\smalformed\sand\sin\sneed\sof\sa\swal-index\srebuild.
-D 2010-05-21T13:16:19
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in a5cad1f8f3e021356bfcc6c77dc16f6f1952bbc3
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -227,7 +224,7 @@ F src/vdbeblob.c 5327132a42a91e8b7acfb60b9d2c3b1c5c863e0e
 F src/vdbemem.c 2a82f455f6ca6f78b59fb312f96054c04ae0ead1
 F src/vdbetrace.c 864cef96919323482ebd9986f2132435115e9cc2
 F src/vtab.c a0f8a40274e4261696ef57aa806de2776ab72cda
-F src/wal.c 1c3abceacad9659ecd1558be75a2114d953d3b7e
+F src/wal.c c05f4091810a4cf4ff0e87f667c6e6341e143516
 F src/wal.h 434f76f51225bb614e43ccb6bd2341541ba6a06e
 F src/walker.c 3112bb3afe1d85dc52317cb1d752055e9a781f8f
 F src/where.c 75fee9e255b62f773fcadd1d1f25b6f63ac7a356
@@ -765,7 +762,7 @@ F test/vtab_alter.test 9e374885248f69e251bdaacf480b04a197f125e5
 F test/vtab_err.test 0d4d8eb4def1d053ac7c5050df3024fd47a3fbd8
 F test/vtab_shared.test 0eff9ce4f19facbe0a3e693f6c14b80711a4222d
 F test/wal.test 90afd254ece957a716751b1c35fac02d6353c2a7
-F test/wal2.test c9f470f7e4f09274a7a4d35dbbae8587115c6e19
+F test/wal2.test 6033cec945f51e3fc19502a69995aecb4252ca03
 F test/walbak.test e7650a26eb4b8abeca9b145b1af1e63026dde432
 F test/walcrash.test f6d5fb2bb108876f04848720a488065d9deef69f
 F test/walfault.test 98df47444944a6db2161eed5cef71d6c00bcb8c3
@@ -816,14 +813,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P 1bd011c9fed5ef29fb616b4d0a52df3b82221b1f
+P 1a4eb3a3efe86c7caff4d9a5894953bce378f841
-R b1aca10baf167dbb95ab7e54f5a950e6
+R 8ca2ea872b35ad91571755768a000a84
-U drh
+U dan
-Z 69b1bc82a1680c243dd4a43f4faa2d67
+Z 71ea7d7c3c51659a819f7c811c09c6cb
------BEGIN PGP SIGNATURE-----
-Version: GnuPG v1.4.6 (GNU/Linux)
-
-iD8DBQFL9oenoxKgR168RlERAhg+AJ9n9qywdfuiNJpDkY+WtSlKP+eZVgCffwF8
-SmDbNBLJmDSM4k/xfAbThXY=
-=j0sy
------END PGP SIGNATURE-----

manifest.uuid

@@ -1 +1 @@
-1a4eb3a3efe86c7caff4d9a5894953bce378f841
+36795c2b23a78978528cace193e386138adacd41

src/wal.c

@@ -193,8 +193,9 @@
 ** second reader using K1 will see additional values that were inserted
 ** later, which is exactly what reader two wants.  
 **
-** When a rollback occurs, the value of K is decreased.  This has the
+** When a rollback occurs, the value of K is decreased. Hash table entries
-** effect of automatically removing entries from the hash table.
+** that correspond to frames greater than the new K value are removed
+** from the hash table at this point.
 */
 #ifndef SQLITE_OMIT_WAL
 
@@ -644,10 +645,10 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
 
     walHashFind(pWal, iFrame, &aHash, &aPgno, &iZero);
     idx = iFrame - iZero;
-    if( idx==1 ) memset((void*)aHash, 0xff, HASHTABLE_NBYTE);
+    if( idx==1 ) memset((void*)aHash, 0, HASHTABLE_NBYTE);
     assert( idx <= HASHTABLE_NSLOT/2 + 1 );
     aPgno[iFrame] = iPage;
-    for(iKey=walHash(iPage); aHash[iKey]<idx; iKey=walNextHash(iKey)){
+    for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
       assert( nCollide++ < idx );
     }
     aHash[iKey] = idx;
@@ -1382,9 +1383,9 @@ int sqlite3WalRead(
     walHashFind(pWal, iHash, &aHash, &aPgno, &iZero);
     mxHash = iLast - iZero;
     if( mxHash > HASHTABLE_NPAGE )  mxHash = HASHTABLE_NPAGE;
-    for(iKey=walHash(pgno); aHash[iKey]<=mxHash; iKey=walNextHash(iKey)){
+    for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
       u32 iFrame = aHash[iKey] + iZero;
-      if( ALWAYS(iFrame<=iLast) && aPgno[iFrame]==pgno && iFrame>iRead ){
+      if( iFrame<=iLast && aPgno[iFrame]==pgno && iFrame>iRead ){
         iRead = iFrame;
       }
     }
@@ -1465,6 +1466,40 @@ int sqlite3WalWriteLock(Wal *pWal, int op){
   return rc;
 }
 
+/*
+** Remove entries from zero or more hash-table indexes in the wal-index 
+** file.
+**
+** This function is called when rolling back a transaction or savepoint
+** transaction in WAL mode. Argument iNewMx is the value that 
+** Wal.hdr.mxFrame will be set to following the rollback. Argument iOldMx
+** is the value that it had before the rollback. This function removes 
+** entries that refer to frames with frame numbers greater than iNewMx 
+** from the hash table that contains the entry associated with iNewMx.
+** It is not necessary to remove any entries from any subsequent hash
+** tables, as they will be zeroed by walIndexAppend() before they are
+** next used.
+*/
+static void walClearHash(Wal *pWal, u32 iOldMx, u32 iNewMx){
+  if( iOldMx>iNewMx ){
+    volatile HASHTABLE_DATATYPE *aHash;     /* Pointer to hash table to clear */
+    volatile u32 *unused1;                  /* Only to satisfy walHashFind() */
+    u32 iZero;                              /* frame == (aHash[x]+iZero) */
+    int iLimit;                             /* Zero values greater than this */
+
+    walHashFind(pWal, iNewMx+1, &aHash, &unused1, &iZero);
+    iLimit = iNewMx - iZero;
+    if( iLimit>0 ){
+      int i;                      /* Used to iterate through aHash[] */
+      for(i=1; i<=HASHTABLE_NPAGE; i++){
+        if( aHash[i]>iLimit ){
+          aHash[i] = 0;
+        }
+      }
+    }
+  }
+}
+
 /*
 ** If any data has been written (but not committed) to the log file, this
 ** function moves the write-pointer back to the start of the transaction.
@@ -1490,6 +1525,9 @@ int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
       assert( pWal->lockState==SQLITE_SHM_WRITE );
       rc = xUndo(pUndoCtx, pWal->pWiData[walIndexEntry(iFrame)]);
     }
+    if( rc==SQLITE_OK ){
+      walClearHash(pWal, iMax, pWal->hdr.mxFrame);
+    }
     walIndexUnmap(pWal);
   }
   return rc;
@@ -1510,6 +1548,11 @@ int sqlite3WalSavepointUndo(Wal *pWal, u32 iFrame){
   int rc = SQLITE_OK;
   assert( pWal->lockState==SQLITE_SHM_WRITE );
 
+  rc = walIndexMap(pWal, walMappingSize(pWal->hdr.mxFrame));
+  if( rc==SQLITE_OK ){
+    walClearHash(pWal, pWal->hdr.mxFrame, iFrame);
+    walIndexUnmap(pWal);
+  }
   pWal->hdr.mxFrame = iFrame;
   return rc;
 }

test/wal2.test

@@ -600,7 +600,32 @@ do_test wal2-6.5.2 {
 do_test wal2-6.5.3 {
   execsql { PRAGMA wal_checkpoint }
 } {}
-
 db close
 
+#-------------------------------------------------------------------------
+# Test a theory about the checksum algorithm. Theory was false and this
+# test did not provoke a bug.
+file delete -force test.db test.db-wal test.db-journal
+do_test wal2-7.1.1 {
+  sqlite3 db test.db
+  execsql {
+    PRAGMA page_size = 4096;
+    PRAGMA journal_mode = WAL;
+    CREATE TABLE t1(a, b);
+  }
+  file size test.db
+} {4096}
+do_test wal2-7.1.2 {
+  file copy -force test.db test2.db
+  file copy -force test.db-wal test2.db-wal
+  hexio_write test2.db-wal 48 FF
+} {1}
+do_test wal2-7.1.3 {
+  sqlite3 db2 test2.db
+  execsql { PRAGMA wal_checkpoint } db2
+  execsql { SELECT * FROM sqlite_master } db2
+} {}
+db2 close
+
 finish_test
+