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Fix a bug in btree.c that caused it to report a database as being

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corrupt if it used one of the last 6 slots in a freelist trunk page.
Continue to never use those last 6 slots so that databases from newer
versions are still readable with older versions. (CVS 5344)

FossilOrigin-Name: b8ff6b0a3dc2ccc51519c764a092822968a09b10
This commit is contained in:
drh
2008-07-04 17:52:42 +00:00
parent bb50e7ad76
commit 45b1fac0ac
3 changed files with 24 additions and 12 deletions
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20
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.470 2008/06/28 15:33:25 danielk1977 Exp $
** $Id: btree.c,v 1.471 2008/07/04 17:52:43 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -4051,7 +4051,7 @@ static int allocateBtreePage(
*ppPage = pTrunk;
pTrunk = 0;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else if( k>pBt->usableSize/4 - 8 ){
}else if( k>pBt->usableSize/4 - 2 ){
/* Value of k is out of range. Database corruption */
rc = SQLITE_CORRUPT_BKPT;
goto end_allocate_page;
@@ -4271,7 +4271,19 @@ static int freePage(MemPage *pPage){
k = get4byte(&pTrunk->aData[4]);
if( k>=pBt->usableSize/4 - 8 ){
/* The trunk is full. Turn the page being freed into a new
** trunk page with no leaves. */
** trunk page with no leaves.
**
** Note that the trunk page is not really full until it contains
** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
** coded. But due to a coding error in versions of SQLite prior to
** 3.6.0, databases with freelist trunk pages holding more than
** usableSize/4 - 8 entries will be reported as corrupt. In order
** to maintain backwards compatibility with older versions of SQLite,
** we will contain to restrict the number of entries to usableSize/4 - 8
** for now. At some point in the future (once everyone has upgraded
** to 3.6.0 or later) we should consider fixing the conditional above
** to read "usableSize/4-2" instead of "usableSize/4-8".
*/
rc = sqlite3PagerWrite(pPage->pDbPage);
if( rc==SQLITE_OK ){
put4byte(pPage->aData, pTrunk->pgno);
@@ -6498,7 +6510,7 @@ static void checkList(
checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0, zContext);
}
#endif
if( n>pCheck->pBt->usableSize/4-8 ){
if( n>pCheck->pBt->usableSize/4-2 ){
checkAppendMsg(pCheck, zContext,
"freelist leaf count too big on page %d", iPage);
N--;