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Fix a recently introduced problem with deleting entries from index tables. (CVS 5754)

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FossilOrigin-Name: 83c064cae481ca95b7107e22e98fc599fe85a2da
This commit is contained in:
danielk1977
2008-09-30 09:31:45 +00:00
parent d94b0556f8
commit 2f78fc66b5
3 changed files with 68 additions and 14 deletions
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66
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 1.520 2008/09/29 16:41:32 danielk1977 Exp $
** $Id: btree.c,v 1.521 2008/09/30 09:31:45 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
@@ -5883,7 +5883,6 @@ int sqlite3BtreeDelete(BtCursor *pCur){
*/
BtCursor leafCur;
MemPage *pLeafPage;
int iLeafIdx;
unsigned char *pNext;
int notUsed;
@@ -5892,16 +5891,17 @@ int sqlite3BtreeDelete(BtCursor *pCur){
sqlite3BtreeGetTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc==SQLITE_OK ){
assert( leafCur.aiIdx[leafCur.iPage]==0 );
pLeafPage = leafCur.apPage[leafCur.iPage];
iLeafIdx = leafCur.aiIdx[leafCur.iPage];
rc = sqlite3PagerWrite(pLeafPage->pDbPage);
}
if( rc==SQLITE_OK ){
int leafCursorInvalid = 0;
u16 szNext;
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %d\n",
pCur->pgnoRoot, pPage->pgno, pLeafPage->pgno));
dropCell(pPage, idx, cellSizePtr(pPage, pCell));
pNext = findCell(pLeafPage, iLeafIdx);
pNext = findCell(pLeafPage, 0);
szNext = cellSizePtr(pLeafPage, pNext);
assert( MX_CELL_SIZE(pBt)>=szNext+4 );
allocateTempSpace(pBt);
@@ -5912,12 +5912,66 @@ int sqlite3BtreeDelete(BtCursor *pCur){
if( rc==SQLITE_OK ){
rc = insertCell(pPage, idx, pNext-4, szNext+4, tempCell, 0);
}
if( (pPage->nOverflow>0 || (pPage->nFree > pBt->usableSize*2/3)) &&
(pLeafPage->nFree+2+szNext > pBt->usableSize*2/3)
){
/* This branch is taken if the internal node is now either over or
** underfull and the leaf node will be underfull after the just cell
** copied to the internal node is deleted from it. This is a special
** case because the call to balance() to correct the internal node
** may change the tree structure and invalidate the contents of
** the leafCur.apPage[] and leafCur.aiIdx[] arrays, which will be
** used by the balance() required to correct the underfull leaf
** node.
**
** The formula used in the expression above are based on facets of
** the SQLite file-format that do not change over time.
*/
leafCursorInvalid = 1;
}
if( rc==SQLITE_OK ){
put4byte(findOverflowCell(pPage, idx), pgnoChild);
rc = balance(pCur, 0);
}
if( rc==SQLITE_OK && leafCursorInvalid ){
/* The leaf-node is now underfull and so the tree needs to be
** rebalanced. However, the balance() operation on the internal
** node above may have modified the structure of the B-Tree and
** so the current contents of leafCur.apPage[] and leafCur.aiIdx[]
** may not be trusted.
**
** It is not possible to copy the ancestry from pCur, as the same
** balance() call has invalidated the pCur->apPage[] and aiIdx[]
** arrays.
**
** The call to saveCursorPosition() below internally saves the
** key that leafCur is currently pointing to. Currently, there
** are two copies of that key in the tree - one here on the leaf
** page and one on some internal node in the tree. The copy on
** the leaf node is always the next key in tree-order after the
** copy on the internal node. So, the call to sqlite3BtreeNext()
** calls restoreCursorPosition() to point the cursor to the copy
** stored on the internal node, then advances to the next entry,
** which happens to be the copy of the key on the internal node.
** Net effect: leafCur is pointing back where
*/
#ifndef NDEBUG
Pgno leafPgno = pLeafPage->pgno;
#endif
rc = saveCursorPosition(&leafCur);
if( rc==SQLITE_OK ){
rc = sqlite3BtreeNext(&leafCur, &notUsed);
}
pLeafPage = leafCur.apPage[leafCur.iPage];
assert( pLeafPage->pgno==leafPgno );
assert( leafCur.aiIdx[leafCur.iPage]==0 );
}
if( rc==SQLITE_OK ){
dropCell(pLeafPage, iLeafIdx, szNext);
dropCell(pLeafPage, 0, szNext);
rc = balance(&leafCur, 0);
}
}
@@ -7026,7 +7080,7 @@ static int btreeCopyFile(Btree *pTo, Btree *pFrom){
}
memcpy(zTo, zFrom, nCopy);
sqlite3PagerUnref(pFromPage);
sqlite3PagerUnref(pFromPage);
}
}