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Avoid treating nonrequired nbtree keys as required.
authorPeter Geoghegan <pg@bowt.ie>
Fri, 2 May 2025 21:50:58 +0000 (17:50 -0400)
committerPeter Geoghegan <pg@bowt.ie>
Fri, 2 May 2025 21:50:58 +0000 (17:50 -0400)
Consistently prevent nbtree array advancement from treating a scankey as
required when operating in pstate.forcenonrequired mode.  Otherwise, we
risk a NULL pointer dereference.  This was possible in the path where
_bt_check_compare is called to recheck a tuple that advanced all of the
scan's arrays to matching values: its continuescan=false handling
expects _bt_advance_array_keys to have been called with a valid pstate,
but it'll always be NULL during sktrig_required=false calls (which is
how _bt_advance_array_keys must be called when pstate.forcenonrequired).

Oversight in commit 8a510275, which optimized nbtree search scan key
comparisons.

Author: Peter Geoghegan <pg@bowt.ie>
Reported-By: Mark Dilger <mark.dilger@enterprisedb.com>
Discussion: https://postgr.es/m/CAHgHdKsn2W=gPBmj7p6MjQFvxB+zZDBkwTSg0o3f5Hh8rkRrsA@mail.gmail.com
Discussion: https://postgr.es/m/CAH2-WzmodSE+gpTd1CRGU9ez8ytyyDS+Kns2r9NzgUp1s56kpw@mail.gmail.com

src/backend/access/nbtree/nbtutils.c patch | blob | blame | history

diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index 11802a4c21518e79b605c8909cbf1036a06a4342..adfa2fd292f7fd9e4986268d0b59ef402c594050 100644 (file)
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -1826,7 +1826,7 @@ _bt_advance_array_keys(IndexScanDesc scan, BTReadPageState *pstate,
 
        /* Recheck _bt_check_compare on behalf of caller */
        if (_bt_check_compare(scan, dir, tuple, tupnatts, tupdesc, false,
-                             false, &continuescan,
+                             !sktrig_required, &continuescan,
                              &nsktrig) &&
            !so->scanBehind)
        {
@@ -2799,8 +2799,6 @@ _bt_check_compare(IndexScanDesc scan, ScanDirection dir,
 {
    BTScanOpaque so = (BTScanOpaque) scan->opaque;
 
-   Assert(!forcenonrequired || advancenonrequired);
-
    *continuescan = true;       /* default assumption */
 
    for (; *ikey < so->numberOfKeys; (*ikey)++)
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