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Fix nbtree lookahead overflow bug.

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Add bounds checking to nbtree's lookahead/skip-within-a-page mechanism.
Otherwise it's possible for cases with lots of before-array-keys tuples
to overflow an int16 variable, causing the mechanism to generate an out
of bounds page offset number.

Oversight in commit 5bf748b8, which enhanced nbtree ScalarArrayOp
execution.

Reported-By: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/6c68ac42-bbb5-8b24-103e-af0e279c536f@gmail.com
Backpatch: 17-, where nbtree SAOP execution was enhanced.
This commit is contained in:
Peter Geoghegan 2024-08-26 11:29:15 -04:00
parent dbe37f1adb
commit 09a8407dbf
1 changed files with 1 additions and 1 deletions
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src/backend/access/nbtree/nbtutils.c
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@ -4091,7 +4091,7 @@ _bt_checkkeys_look_ahead(IndexScanDesc scan, BTReadPageState *pstate,
*/
if (!pstate->targetdistance)
pstate->targetdistance = LOOK_AHEAD_DEFAULT_DISTANCE;
else
else if (pstate->targetdistance < MaxIndexTuplesPerPage / 2)
pstate->targetdistance *= 2;
/* Don't read past the end (or before the start) of the page, though */