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Detect when a VdbeCursor is still pointing at a valid row but that row has

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moved, and invalidated the return from prior sqlite3BtreeDataFetch() or
sqlite3BtreeKeyFetch() calls.

FossilOrigin-Name: e6798871ce94961135762669af418cd78540c121
This commit is contained in:
drh
2014-03-25 11:00:21 +00:00
parent b22f38a779
commit 86dd3716b9
4 changed files with 29 additions and 14 deletions
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23
src/btree.c
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@@ -746,20 +746,32 @@ static int btreeRestoreCursorPosition(BtCursor *pCur){
** at is deleted out from under them.
**
** This routine returns an error code if something goes wrong. The
** integer *pHasMoved is set to one if the cursor has moved and 0 if not.
** integer *pHasMoved is set as follows:
**
** 0: The cursor is unchanged
** 1: The cursor is still pointing at the same row, but the pointers
** returned by sqlite3BtreeKeyFetch() or sqlite3BtreeDataFetch()
** might now be invalid because of a balance() or other change to the
** b-tree.
** 2: The cursor is no longer pointing to the row. The row might have
** been deleted out from under the cursor.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
int rc;
if( pCur->eState==CURSOR_VALID ){
*pHasMoved = 0;
return SQLITE_OK;
}
rc = restoreCursorPosition(pCur);
if( rc ){
*pHasMoved = 1;
*pHasMoved = 2;
return rc;
}
if( pCur->eState!=CURSOR_VALID || NEVER(pCur->skipNext!=0) ){
*pHasMoved = 1;
*pHasMoved = 2;
}else{
*pHasMoved = 0;
*pHasMoved = 1;
}
return SQLITE_OK;
}
@@ -4188,10 +4200,13 @@ static const void *fetchPayload(
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
assert( cursorHoldsMutex(pCur) );
assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
assert( pCur->info.nSize>0 );
#if 0
if( pCur->info.nSize==0 ){
btreeParseCell(pCur->apPage[pCur->iPage], pCur->aiIdx[pCur->iPage],
&pCur->info);
}
#endif
*pAmt = pCur->info.nLocal;
return (void*)(pCur->info.pCell + pCur->info.nHeader);
}