Do not load the root-page of a b-tree table/index when opening a cursor. Instead, allow it to be loaded when the cursor is first used (in function moveToRoot()). Also move the root-page flags sanity checks that were a part of the OP_OpenRead/OpenWrite opcodes into the moveToRoot() function. (CVS 6856)

FossilOrigin-Name: 06dcfe72a6ff3f63639eeb00ec5b5022d10fc55b

manifest

@@ -1,5 +1,5 @@
-C If\san\serror\soccurs\sin\sPagerBegin(),\scall\spager_end_transaction()\sto\sreset\sthe\sinternal\sstate\sof\sthe\spager\sobject.\s(CVS\s6855)
+C Do\snot\sload\sthe\sroot-page\sof\sa\sb-tree\stable/index\swhen\sopening\sa\scursor.\sInstead,\sallow\sit\sto\sbe\sloaded\swhen\sthe\scursor\sis\sfirst\sused\s(in\sfunction\smoveToRoot()).\sAlso\smove\sthe\sroot-page\sflags\ssanity\schecks\sthat\swere\sa\spart\sof\sthe\sOP_OpenRead/OpenWrite\sopcodes\sinto\sthe\smoveToRoot()\sfunction.\s(CVS\s6856)
-D 2009-07-07T13:56:24
+D 2009-07-07T15:47:12
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in df9359da7a726ccb67a45db905c5447d5c00c6ef
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -106,7 +106,7 @@ F src/auth.c 802a9439dfa0b8c208b10055cba400e82ef18025
 F src/backup.c 6f1c2d9862c8a3feb7739dfcca02c1f5352e37f3
 F src/bitvec.c 0ef0651714728055d43de7a4cdd95e703fac0119
 F src/btmutex.c 9b899c0d8df3bd68f527b0afe03088321b696d3c
-F src/btree.c 8f4c2ebdc9f0e0139f5878fac8ac96b12528b014
+F src/btree.c 0cc9c503015fa4970b41833c1a253410ad055ce5
 F src/btree.h e761619e76a1125d2d82bd3613b5a7ac7d1ee6f7
 F src/btreeInt.h b31e5ac04181c7e2892c33ab06228c551df6233c
 F src/build.c 867028ee9f63f7bc8eb8d4a720bb98cf9b9a12b4
@@ -204,7 +204,7 @@ F src/update.c a1bbe774bce495d62dce3df3f42a5f04c1de173a
 F src/utf.c 9541d28f40441812c0b40f00334372a0542c00ff
 F src/util.c 861d5b5c58be4921f0a254489ea94cb15f550ef8
 F src/vacuum.c 3fe0eebea6d2311c1c2ab2962887d11f7a4dcfb0
-F src/vdbe.c bdf25930bddbf57b18a0be7b1127b357306d2094
+F src/vdbe.c 4f702761ce1829192e191de461671e214a778386
 F src/vdbe.h 35a648bc3279a120da24f34d9a25213ec15daf8a
 F src/vdbeInt.h 831c254a6eef237ef4664c8381a0137586567007
 F src/vdbeapi.c 0ab8ada7260b32031ca97f338caecf0812460624
@@ -740,7 +740,7 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl 672f81d693a03f80f5ae60bfefacd8a349e76746
-P ec1e27e33b89e809a03e4140b351f6c8674c0233
+P ea7ed16628da29cf4a127a25cbac8ae553e2ac1f
-R e28c07bc21fb6fc8bda63e0e4a6adcc7
+R 6a1dd7b7ae30a801861a4c4d841bbfb1
 U danielk1977
-Z 890ee77caf3f4dd632bdc59421b0f5cb
+Z 0d744ad2ad4529f2f9b6cce7c155c49a

manifest.uuid

@@ -1 +1 @@
-ea7ed16628da29cf4a127a25cbac8ae553e2ac1f
+06dcfe72a6ff3f63639eeb00ec5b5022d10fc55b

src/btree.c

@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.655 2009/07/07 11:39:59 drh Exp $
+** $Id: btree.c,v 1.656 2009/07/07 15:47:12 danielk1977 Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** See the header comment on "btreeInt.h" for additional information.
@@ -3238,15 +3238,10 @@ static int btreeCursor(
     return SQLITE_EMPTY;
   }
 
-  pCur->pgnoRoot = (Pgno)iTable;
-  rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]);
-  if( rc!=SQLITE_OK ){
-    assert( pCur->apPage[0]==0 );
-    return rc;
-  }
-
   /* Now that no other errors can occur, finish filling in the BtCursor
   ** variables and link the cursor into the BtShared list.  */
+  pCur->pgnoRoot = (Pgno)iTable;
+  pCur->iPage = -1;
   pCur->pKeyInfo = pKeyInfo;
   pCur->pBtree = p;
   pCur->pBt = pBt;
@@ -3991,6 +3986,7 @@ static int moveToRoot(BtCursor *pCur){
     for(i=1; i<=pCur->iPage; i++){
       releasePage(pCur->apPage[i]);
     }
+    pCur->iPage = 0;
   }else{
     if( 
       SQLITE_OK!=(rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->apPage[0]))
@@ -3998,11 +3994,20 @@ static int moveToRoot(BtCursor *pCur){
       pCur->eState = CURSOR_INVALID;
       return rc;
     }
+    pCur->iPage = 0;
+
+    /* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
+    ** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
+    ** NULL, the caller expects a table b-tree. If this is not the case,
+    ** return an SQLITE_CORRUPT error.  */
+    assert( pCur->apPage[0]->intKey==1 || pCur->apPage[0]->intKey==0 );
+    if( (pCur->pKeyInfo==0)!=pCur->apPage[0]->intKey ){
+      return SQLITE_CORRUPT_BKPT;
+    }
   }
 
   pRoot = pCur->apPage[0];
   assert( pRoot->pgno==pCur->pgnoRoot );
-  pCur->iPage = 0;
   pCur->aiIdx[0] = 0;
   pCur->info.nSize = 0;
   pCur->atLast = 0;

src/vdbe.c

@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.869 2009/07/03 16:25:07 danielk1977 Exp $
+** $Id: vdbe.c,v 1.870 2009/07/07 15:47:12 danielk1977 Exp $
 */
 #include "sqliteInt.h"
 #include "vdbeInt.h"
@@ -2913,7 +2913,6 @@ case OP_OpenWrite: {
   Btree *pX;
   VdbeCursor *pCur;
   Db *pDb;
-  int flags;
 
   nField = 0;
   pKeyInfo = 0;
@@ -2961,45 +2960,22 @@ case OP_OpenWrite: {
   rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
   pCur->pKeyInfo = pKeyInfo;
 
-  switch( rc ){
+  /* Since it performs no memory allocation or IO, the only values that
-    case SQLITE_OK: {
+  ** sqlite3BtreeCursor() may return are SQLITE_EMPTY and SQLITE_OK. 
-      flags = sqlite3BtreeFlags(pCur->pCursor);
+  ** SQLITE_EMPTY is only returned when attempting to open the table
-
+  ** rooted at page 1 of a zero-byte database.  */
-      /* Sanity checking.  Only the lower four bits of the flags byte should
+  assert( rc==SQLITE_EMPTY || rc==SQLITE_OK );
-      ** be used.  Bit 3 (mask 0x08) is unpredictable.  The lower 3 bits
+  if( rc==SQLITE_EMPTY ){
-      ** (mask 0x07) should be either 5 (intkey+leafdata for tables) or
+    pCur->pCursor = 0;
-      ** 2 (zerodata for indices).  If these conditions are not met it can
+    rc = SQLITE_OK;
-      ** only mean that we are dealing with a corrupt database file.
-      ** Note:  All of the above is checked already in sqlite3BtreeCursor().
-      */
-      assert( (flags & 0xf0)==0 );
-      assert( (flags & 0x07)==5 || (flags & 0x07)==2 );
-
-      pCur->isTable = (flags & BTREE_INTKEY)!=0 ?1:0;
-      pCur->isIndex = (flags & BTREE_ZERODATA)!=0 ?1:0;
-      /* If P4==0 it means we are expected to open a table.  If P4!=0 then
-      ** we expect to be opening an index.  If this is not what happened,
-      ** then the database is corrupt
-      */
-      if( (pCur->isTable && pOp->p4type==P4_KEYINFO)
-       || (pCur->isIndex && pOp->p4type!=P4_KEYINFO) ){
-        rc = SQLITE_CORRUPT_BKPT;
-        goto abort_due_to_error;
-      }
-      break;
-    }
-    case SQLITE_EMPTY: {
-      pCur->isTable = pOp->p4type!=P4_KEYINFO;
-      pCur->isIndex = !pCur->isTable;
-      pCur->pCursor = 0;
-      rc = SQLITE_OK;
-      break;
-    }
-    default: {
-      assert( rc!=SQLITE_BUSY );  /* Busy conditions detected earlier */
-      goto abort_due_to_error;
-    }
   }
+
+  /* Set the VdbeCursor.isTable and isIndex variables. Previous versions of
+  ** SQLite used to check if the root-page flags were sane at this point
+  ** and report database corruption if they were not, but this check has
+  ** since moved into the btree layer.  */  
+  pCur->isTable = pOp->p4type!=P4_KEYINFO;
+  pCur->isIndex = !pCur->isTable;
   break;
 }