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Early exit if one of the inner loops of a 3-way or larger join is an

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empty table.

FossilOrigin-Name: eaad6ac707a5960d9518d4049b7b1759e7512727ce87be3c402408144bda0a97
This commit is contained in:
drh
2025-07-02 14:53:48 +00:00
parent 216676664d
commit 33f3273705
7 changed files with 37 additions and 26 deletions
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25
src/btree.c
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@@ -5667,21 +5667,28 @@ 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.
/* Set *pRes to 1 (true) if the BTree pointed to by cursor pCur contains zero
** rows of content. Set *pRes to 0 (false) if the table contains content.
** Return SQLITE_OK on success or some error code (ex: SQLITE_NOMEM) if
** something goes wrong.
*/
int sqlite3BtreeIsEmpty(BtCursor *pCur){
int sqlite3BtreeIsEmpty(BtCursor *pCur, int *pRes){
int rc;
assert( cursorOwnsBtShared(pCur) );
assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
if( pCur->eState==CURSOR_VALID ) return 0;
if( pCur->eState==CURSOR_VALID ){
*pRes = 0;
return SQLITE_OK;
}
rc = moveToRoot(pCur);
return rc==SQLITE_EMPTY;
if( rc==SQLITE_EMPTY ){
*pRes = 1;
rc = SQLITE_OK;
}else{
*pRes = 0;
}
return rc;
}
#ifdef SQLITE_DEBUG