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If the LHS for an EXCEPT or INTERSECT operator is empty, skip over the

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computation of the RHS.

FossilOrigin-Name: 13f096ae8a850a05d4a8684561066f11693ee66289e6568c44ef32822cca06f6
This commit is contained in:
drh
2025-07-02 13:19:24 +00:00
parent 6245e5a46b
commit 216676664d
6 changed files with 64 additions and 10 deletions
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17
src/btree.c
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@@ -5667,6 +5667,23 @@ int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
return rc;
}
/* Return true if the BTree pointed to by cursor pCur contains zero
** rows of content. Return false if the table contains content or if
** if there is some kind of error. This routine is used as an optimization.
** Returning false (a false negative) will always result in a correct
** answer, though perhaps more slowly. But a false positive (an incorrect
** return of true) can yield an incorrect answer.
*/
int sqlite3BtreeIsEmpty(BtCursor *pCur){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
if( pCur->eState==CURSOR_VALID ) return 0;
rc = moveToRoot(pCur);
return rc==SQLITE_EMPTY;
}
#ifdef SQLITE_DEBUG
/* The cursors is CURSOR_VALID and has BTCF_AtLast set. Verify that
** this flags are true for a consistent database.