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pgsql: Fix nbtree skip array parallel alloc accounting. 2+ messages / 1 participants [nested] [flat]
* pgsql: Fix nbtree skip array parallel alloc accounting. @ 2026-04-29 15:23 Peter Geoghegan <pg@bowt.ie> 0 siblings, 0 replies; 2+ messages in thread From: Peter Geoghegan @ 2026-04-29 15:23 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Fix nbtree skip array parallel alloc accounting. btestimateparallelscan neglected to add btps_arrElems[] space overhead for skip array scan keys that were later output by nbtree preprocessing. Skip arrays don't actually need to use this space, but a scan with a subsequent SAOP array will need to subscript btps_arrElems[] using a simple so->arrayKeys[]-wise offset. so->arrayKeys[] has entries for both kinds of arrays. As a result of this oversight, it was possible for an index scan with a skip array and a lower-order SAOP array to write past the allocated shared memory boundary when storing the SAOP array's cur_elem. In practice the problem seems to be limited to scans with many skipped index columns, since our general approach to estimating the amount of shared memory that will be required is fairly conservative. To fix, have btestimateparallelscan request an extra sizeof(int) space for key columns that might require a skip array later on. Oversight in commit 92fe23d9, which added the nbtree skip scan optimization. Author: Siddharth Kothari <sidkot@google.com> Discussion: https://postgr.es/m/CAGCUe0Lwk3C0qdkBa+OLpYc7yXwW=pbaz8Sju4xMXEQAmyp+5g@mail.gmail.com Backpatch-through: 18 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/1e71970d2d2bc38dd542f029098e05ab80fd8294 Modified Files -------------- src/backend/access/nbtree/nbtree.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
* pgsql: Fix nbtree skip array parallel alloc accounting. @ 2026-04-29 15:23 Peter Geoghegan <pg@bowt.ie> 0 siblings, 0 replies; 2+ messages in thread From: Peter Geoghegan @ 2026-04-29 15:23 UTC (permalink / raw) To: pgsql-committers@lists.postgresql.org Fix nbtree skip array parallel alloc accounting. btestimateparallelscan neglected to add btps_arrElems[] space overhead for skip array scan keys that were later output by nbtree preprocessing. Skip arrays don't actually need to use this space, but a scan with a subsequent SAOP array will need to subscript btps_arrElems[] using a simple so->arrayKeys[]-wise offset. so->arrayKeys[] has entries for both kinds of arrays. As a result of this oversight, it was possible for an index scan with a skip array and a lower-order SAOP array to write past the allocated shared memory boundary when storing the SAOP array's cur_elem. In practice the problem seems to be limited to scans with many skipped index columns, since our general approach to estimating the amount of shared memory that will be required is fairly conservative. To fix, have btestimateparallelscan request an extra sizeof(int) space for key columns that might require a skip array later on. Oversight in commit 92fe23d9, which added the nbtree skip scan optimization. Author: Siddharth Kothari <sidkot@google.com> Discussion: https://postgr.es/m/CAGCUe0Lwk3C0qdkBa+OLpYc7yXwW=pbaz8Sju4xMXEQAmyp+5g@mail.gmail.com Backpatch-through: 18 Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/748d871b7cb08302ef312b665bd64012f19fc16c Modified Files -------------- src/backend/access/nbtree/nbtree.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2026-04-29 15:23 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-04-29 15:23 pgsql: Fix nbtree skip array parallel alloc accounting. Peter Geoghegan <pg@bowt.ie> 2026-04-29 15:23 pgsql: Fix nbtree skip array parallel alloc accounting. Peter Geoghegan <pg@bowt.ie>
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