Avoid the 1-based indexing on the WalHashLoc.aPgno[] array. Make it 0-indexed

instead.

FossilOrigin-Name: 28f5f709b4b28ba7f6f56bdd4a9e8c04d0d2df90d13d6df1a589fa4a65163f4d

diff --git a/manifest b/manifest
index 4eb388a925f61938a939cfceeb32fbae94d783ac..2c0303812e0d759984b1d23a4f303165bde1201b 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Improve\sthe\scomment\son\swalIndexPage()\sto\smore\saccurately\sdescribe\sthe\npost-conditions.
-D 2021-10-27T19:57:59.451
+C Avoid\sthe\s1-based\sindexing\son\sthe\sWalHashLoc.aPgno[]\sarray.\s\sMake\sit\s0-indexed\ninstead.
+D 2021-10-27T20:23:59.854
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -633,7 +633,7 @@ F src/vdbetrace.c fe0bc29ebd4e02c8bc5c1945f1d2e6be5927ec12c06d89b03ef2a4def34bf8
 F src/vdbevtab.c f99b275366c5fc5e2d99f734729880994ab9500bdafde7fae3b02d562b9d323c
 F src/vtab.c d07cc24dd84b0b51bf05adb187b0d2e6b0cac56cfbc0197995a26d4f8fa5c7e2
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c 2bf6d846140a3ef6ac4dae85e993e98dd304e03641ccef65904744eb85e65e2e
+F src/wal.c 2fd68f0a2e12486a543016ee47828874863c486b8a090989e70627f556ccde32
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
 F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
 F src/where.c ecabef93b0f14442a73eca205fc960428984d75fbdc7d60226b7fc9cac127187
@@ -1929,10 +1929,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 7238d58051bfdcea8f7a4aeab89145849d0659c987df9063aacafe97be6657fe
-R d7b0bf6adaa4481b0cdf4adead947bd2
-T *branch * wal-tuneup
-T *sym-wal-tuneup *
-T -sym-trunk *
+P b619e936455f4001b543a9a58dea2ac9ebd598327d6be01130ca6e7e9764ffe6
+R 0450e5bea2ea312618d6c5cbc7e1928c
 U drh
-Z 903a3bc4a6ff5101d13b9fbd42b22ae8
+Z 2a7a0238c8886bf3fdd3adf1dc184586

diff --git a/manifest.uuid b/manifest.uuid
index 724e8d66eeabffb796c0fedde85e922f2dc780b9..957b241b44c94610dc6414c773fa03948726c73f 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-b619e936455f4001b543a9a58dea2ac9ebd598327d6be01130ca6e7e9764ffe6
\ No newline at end of file
+28f5f709b4b28ba7f6f56bdd4a9e8c04d0d2df90d13d6df1a589fa4a65163f4d
\ No newline at end of file

diff --git a/src/wal.c b/src/wal.c
index 0b01c30f2272ae9d97e9370bad5199339d4502a6..2b53bdc067facb657d98f317e6a195077b483be7 100644 (file)
--- a/src/wal.c
+++ b/src/wal.c
@@ -1000,8 +1000,8 @@ struct WalHashLoc {
 ** slot in the hash table is set to N, it refers to frame number 
 ** (pLoc->iZero+N) in the log.
 **
-** Finally, set pLoc->aPgno so that pLoc->aPgno[1] is the page number of the
-** first frame indexed by the hash table, frame (pLoc->iZero+1).
+** Finally, set pLoc->aPgno so that pLoc->aPgno[0] is the page number of the
+** first frame indexed by the hash table, frame (pLoc->iZero).
 */
 static int walHashGet(
   Wal *pWal,                      /* WAL handle */
@@ -1021,7 +1021,6 @@ static int walHashGet(
     }else{
       pLoc->iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
     }
-    pLoc->aPgno = &pLoc->aPgno[-1];
   }
   return rc;
 }
@@ -1103,8 +1102,9 @@ static void walCleanupHash(Wal *pWal){
   /* Zero the entries in the aPgno array that correspond to frames with
   ** frame numbers greater than pWal->hdr.mxFrame. 
   */
-  nByte = (int)((char *)sLoc.aHash - (char *)&sLoc.aPgno[iLimit+1]);
-  memset((void *)&sLoc.aPgno[iLimit+1], 0, nByte);
+  nByte = (int)((char *)sLoc.aHash - (char *)&sLoc.aPgno[iLimit]);
+  assert( nByte>=0 );
+  memset((void *)&sLoc.aPgno[iLimit], 0, nByte);
 
 #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
   /* Verify that the every entry in the mapping region is still reachable
@@ -1113,11 +1113,11 @@ static void walCleanupHash(Wal *pWal){
   if( iLimit ){
     int j;           /* Loop counter */
     int iKey;        /* Hash key */
-    for(j=1; j<=iLimit; j++){
+    for(j=0; j<iLimit; j++){
       for(iKey=walHash(sLoc.aPgno[j]);sLoc.aHash[iKey];iKey=walNextHash(iKey)){
-        if( sLoc.aHash[iKey]==j ) break;
+        if( sLoc.aHash[iKey]==j+1 ) break;
       }
-      assert( sLoc.aHash[iKey]==j );
+      assert( sLoc.aHash[iKey]==j+1 );
     }
   }
 #endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
@@ -1149,9 +1149,9 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
     ** entire hash table and aPgno[] array before proceeding. 
     */
     if( idx==1 ){
-      int nByte = (int)((u8 *)&sLoc.aHash[HASHTABLE_NSLOT]
-                               - (u8 *)&sLoc.aPgno[1]);
-      memset((void*)&sLoc.aPgno[1], 0, nByte);
+      int nByte = (int)((u8*)&sLoc.aHash[HASHTABLE_NSLOT] - (u8*)sLoc.aPgno);
+      assert( nByte>=0 );
+      memset((void*)sLoc.aPgno, 0, nByte);
     }
 
     /* If the entry in aPgno[] is already set, then the previous writer
@@ -1160,9 +1160,9 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
     ** Remove the remnants of that writers uncommitted transaction from 
     ** the hash-table before writing any new entries.
     */
-    if( sLoc.aPgno[idx] ){
+    if( sLoc.aPgno[idx-1] ){
       walCleanupHash(pWal);
-      assert( !sLoc.aPgno[idx] );
+      assert( !sLoc.aPgno[idx-1] );
     }
 
     /* Write the aPgno[] array entry and the hash-table slot. */
@@ -1170,7 +1170,7 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
     for(iKey=walHash(iPage); sLoc.aHash[iKey]; iKey=walNextHash(iKey)){
       if( (nCollide--)==0 ) return SQLITE_CORRUPT_BKPT;
     }
-    sLoc.aPgno[idx] = iPage;
+    sLoc.aPgno[idx-1] = iPage;
     AtomicStore(&sLoc.aHash[iKey], (ht_slot)idx);
 
 #ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
@@ -1191,19 +1191,18 @@ static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
     */
     if( (idx&0x3ff)==0 ){
       int i;           /* Loop counter */
-      for(i=1; i<=idx; i++){
+      for(i=0; i<idx; i++){
         for(iKey=walHash(sLoc.aPgno[i]);
             sLoc.aHash[iKey];
             iKey=walNextHash(iKey)){
-          if( sLoc.aHash[iKey]==i ) break;
+          if( sLoc.aHash[iKey]==i+1 ) break;
         }
-        assert( sLoc.aHash[iKey]==i );
+        assert( sLoc.aHash[iKey]==i+1 );
       }
     }
 #endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
   }
 
-
   return rc;
 }
 
@@ -1821,7 +1820,6 @@ static int walIteratorInit(Wal *pWal, u32 nBackfill, WalIterator **pp){
       int nEntry;                 /* Number of entries in this segment */
       ht_slot *aIndex;            /* Sorted index for this segment */
 
-      sLoc.aPgno++;
       if( (i+1)==nSegment ){
         nEntry = (int)(iLast - sLoc.iZero);
       }else{
@@ -2960,7 +2958,8 @@ int sqlite3WalSnapshotRecover(Wal *pWal){
 
           rc = walHashGet(pWal, walFramePage(i), &sLoc);
           if( rc!=SQLITE_OK ) break;
-          pgno = sLoc.aPgno[i-sLoc.iZero];
+          assert( i - sLoc.iZero - 1 >=0 );
+          pgno = sLoc.aPgno[i-sLoc.iZero-1];
           iDbOff = (i64)(pgno-1) * szPage;
 
           if( iDbOff+szPage<=szDb ){
@@ -3193,7 +3192,7 @@ int sqlite3WalFindFrame(
     iKey = walHash(pgno);
     while( (iH = AtomicLoad(&sLoc.aHash[iKey]))!=0 ){
       u32 iFrame = iH + sLoc.iZero;
-      if( iFrame<=iLast && iFrame>=pWal->minFrame && sLoc.aPgno[iH]==pgno ){
+      if( iFrame<=iLast && iFrame>=pWal->minFrame && sLoc.aPgno[iH-1]==pgno ){
         assert( iFrame>iRead || CORRUPT_DB );
         iRead = iFrame;
       }