From b75fedcab7916e1c955dbab565b7ad0cee6b37c6 Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Mon, 28 Apr 2025 12:11:08 -0400 Subject: [PATCH] Make NULL tuple values always advance skip arrays. _bt_check_compare neglected to handle a case that can arise when the scan's keys are temporarily treated as nonrequired, as an optimization: whenever a NULL tuple value was encountered that had a skip array whose current element wasn't already NULL, _bt_check_compare failed to advance the array to the NULL element. This allowed _bt_check_compare to fail to return matching tuples containing a NULL value (though only with an array column that came before a skip array column with NULLs, and only during _bt_readpage calls that set pstate.forcenonrequired=true on a page where the higher-order column also had to advance). To fix, teach _bt_check_compare to handle this case just like any other case where a skip array key is unsatisfied and must be advanced directly (due to the key being considered a nonrequired key). Oversight in commit 8a510275, which optimized nbtree search scan key comparisons with skip arrays. Author: Peter Geoghegan Reported-By: Mark Dilger Discussion: https://postgr.es/m/CAHgHdKtLFWZcjr87hMH0hYDHgcifu4Tj7iHz-xh8qsJREt5cqA@mail.gmail.com --- src/backend/access/nbtree/nbtutils.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c index 8b025796127..c899168c995 100644 --- a/src/backend/access/nbtree/nbtutils.c +++ b/src/backend/access/nbtree/nbtutils.c @@ -2920,6 +2920,17 @@ _bt_check_compare(IndexScanDesc scan, ScanDirection dir, if (isNull) { + /* + * Scalar scan key isn't satisfied by NULL tuple value. + * + * If we're treating scan keys as nonrequired, and key is for a + * skip array, then we must attempt to advance the array to NULL + * (if we're successful then the tuple might match the qual). + */ + if (unlikely(forcenonrequired && key->sk_flags & SK_BT_SKIP)) + return _bt_advance_array_keys(scan, NULL, tuple, tupnatts, + tupdesc, *ikey, false); + if (key->sk_flags & SK_BT_NULLS_FIRST) { /* @@ -2958,7 +2969,7 @@ _bt_check_compare(IndexScanDesc scan, ScanDirection dir, } /* - * In any case, this indextuple doesn't match the qual. + * This indextuple doesn't match the qual. */ return false; }