From 7236583ba08dd523850f0a77dc906a006c5bbb15 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Tue, 6 Mar 2007 15:53:44 +0000
Subject: [PATCH] Fixes to the overflow-chain optization of (3672). (CVS 3674)

FossilOrigin-Name: d6986d1e7cba1d114fa06c5560ffc6bb1feb7389
---
 manifest      | 14 +++++++-------
 manifest.uuid |  2 +-
 src/btree.c   | 24 ++++++++++++++----------
 3 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/manifest b/manifest
index c3b8675253..b5068ea11b 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Use\sheap\sinstead\sof\sstack\sfor\slarge\sbuffers\sin\sthe\spager.\sFix\sfor\s#2262.\s(CVS\s3673)
-D 2007-03-06T13:46:00
+C Fixes\sto\sthe\soverflow-chain\soptization\sof\s(3672).\s(CVS\s3674)
+D 2007-03-06T15:53:44
 F Makefile.in 1fe3d0b46e40fd684e1e61f8e8056cefed16de9f
 F Makefile.linux-gcc 2d8574d1ba75f129aba2019f0b959db380a90935
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -57,7 +57,7 @@ F src/alter.c 2c79ec40f65e33deaf90ca493422c74586e481a3
 F src/analyze.c 7d2b7ab9a9c2fd6e55700f69064dfdd3e36d7a8a
 F src/attach.c b11eb4d5d3fb99a10a626956bccc7215f6b68b16
 F src/auth.c 902f4722661c796b97f007d9606bd7529c02597f
-F src/btree.c d42d2b634a5099cd6cb92d4482fba980ddc6635f
+F src/btree.c f5c1b3d88ad62ab4682de37229168a00b87fc948
 F src/btree.h 066444ee25bd6e6accb997bfd2cf5ace14dbcd00
 F src/build.c 6bd68dc730b01c1727738f8e4b5c730eb0ddb421
 F src/callback.c 31d22b4919c7645cbcbb1591ce2453e8c677c558
@@ -435,7 +435,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 6db945f7a7587c8c7adada92f94ac7936b901cf1
-R fd445e52d946f4b2dccfd0401e136fcc
-U danielk1977
-Z 899687d498719bea31167b023df14d79
+P dfe1dffa4515ed6494055887d351863fe0cdb87f
+R d2acbced061dbbf26fe53e64388781c3
+U drh
+Z 244e63934da04ffe6f36fb683b60298b
diff --git a/manifest.uuid b/manifest.uuid
index a02a6aec97..c381dd1f3d 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-dfe1dffa4515ed6494055887d351863fe0cdb87f
\ No newline at end of file
+d6986d1e7cba1d114fa06c5560ffc6bb1feb7389
\ No newline at end of file
diff --git a/src/btree.c b/src/btree.c
index 368b380954..f99277402a 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -9,7 +9,7 @@
 **    May you share freely, never taking more than you give.
 **
 *************************************************************************
-** $Id: btree.c,v 1.337 2007/03/06 11:42:19 drh Exp $
+** $Id: btree.c,v 1.338 2007/03/06 15:53:44 drh Exp $
 **
 ** This file implements a external (disk-based) database using BTrees.
 ** For a detailed discussion of BTrees, refer to
@@ -365,6 +365,7 @@ struct CellInfo {
   u8 *pCell;     /* Pointer to the start of cell content */
   i64 nKey;      /* The key for INTKEY tables, or number of bytes in key */
   u32 nData;     /* Number of bytes of data */
+  u32 nPayload;  /* Total amount of payload */
   u16 nHeader;   /* Size of the cell content header in bytes */
   u16 nLocal;    /* Amount of payload held locally */
   u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */
@@ -944,6 +945,7 @@ static void parseCellPtr(
     pInfo->nKey = x;
     nPayload += x;
   }
+  pInfo->nPayload = nPayload;
   pInfo->nHeader = n;
   if( nPayload<=pPage->maxLocal ){
     /* This is the (easy) common case where the entire payload fits
@@ -1020,6 +1022,7 @@ static int ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell){
   if( pCell ){
     CellInfo info;
     parseCellPtr(pPage, pCell, &info);
+    assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
     if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
       Pgno ovfl = get4byte(&pCell[info.iOverflow]);
       return ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno);
@@ -3876,30 +3879,29 @@ static int clearCell(MemPage *pPage, unsigned char *pCell){
   int rc;
   int nOvfl;
   int ovflPageSize;
-  int nPayload;
 
   parseCellPtr(pPage, pCell, &info);
   if( info.iOverflow==0 ){
     return SQLITE_OK;  /* No overflow pages. Return without doing anything */
   }
   ovflPgno = get4byte(&pCell[info.iOverflow]);
-  nPayload = pPage->intKey ? info.nData : info.nKey;
   ovflPageSize = pBt->usableSize - 4;
-  nOvfl = (nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
-  while( ovflPgno!=0 ){
+  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
+  assert( ovflPgno==0 || nOvfl>0 );
+  while( nOvfl-- ){
     MemPage *pOvfl;
-    nOvfl--;
-    if( ovflPgno>sqlite3pager_pagecount(pBt->pPager) ){
+    if( ovflPgno==0 || ovflPgno>sqlite3pager_pagecount(pBt->pPager) ){
       return SQLITE_CORRUPT_BKPT;
     }
-    rc = getPage(pBt, ovflPgno, &pOvfl, nOvfl==0);
+    rc = getPage(pBt, ovflPgno, &pOvfl, 0);
     if( rc ) return rc;
-    ovflPgno = get4byte(pOvfl->aData);
+    if( nOvfl ){
+      ovflPgno = get4byte(pOvfl->aData);
+    }
     rc = freePage(pOvfl);
     sqlite3pager_unref(pOvfl->aData);
     if( rc ) return rc;
   }
-  assert( nOvfl==0 );
   return SQLITE_OK;
 }
 
@@ -4196,6 +4198,7 @@ static int insertCell(
       */
       CellInfo info;
       parseCellPtr(pPage, pCell, &info);
+      assert( (info.nData+(pPage->intKey?0:info.nKey))==info.nPayload );
       if( (info.nData+(pPage->intKey?0:info.nKey))>info.nLocal ){
         Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);
         int rc = ptrmapPut(pPage->pBt, pgnoOvfl, PTRMAP_OVERFLOW1, pPage->pgno);
@@ -6201,6 +6204,7 @@ static int checkTreePage(
     parseCellPtr(pPage, pCell, &info);
     sz = info.nData;
     if( !pPage->intKey ) sz += info.nKey;
+    assert( sz==info.nPayload );
     if( sz>info.nLocal ){
       int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
       Pgno pgnoOvfl = get4byte(&pCell[info.iOverflow]);