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Only clear VACUUM's read stream strategy once in failsafe mode

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112c268380 restored failsafe vacuum's abandonment of a buffer
access strategy by clearing the ReadBuffersOperations' strategy
references. But it did so in lazy_scan_heap()'s main loop, meaning it
looped through all the ReadBuffersOperations once per block after
failsafe was engaged. Track it with a local flag and clear the strategy
only once.

Reported-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/CAAKRu_Zse14nSNeCgtnE1LUAH8Of7OmYR%2BCc3O_DAzxt3m6T-g%40mail.gmail.com
Backpatch-through: 18
This commit is contained in:
Melanie Plageman
2026-08-07 09:59:55 -04:00
parent 4ea497a926
commit 7c25cdb1eb
1 changed files with 7 additions and 2 deletions
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9
src/backend/access/heap/vacuumlazy.c
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@@ -1206,6 +1206,7 @@ lazy_scan_heap(LVRelState *vacrel)
BlockNumber orig_eager_scan_success_limit =
vacrel->eager_scan_remaining_successes; /* for logging */
Buffer vmbuffer = InvalidBuffer;
bool strategy_cleared = false;
const int initprog_index[] = {
PROGRESS_VACUUM_PHASE,
PROGRESS_VACUUM_TOTAL_HEAP_BLKS,
@@ -1311,10 +1312,14 @@ lazy_scan_heap(LVRelState *vacrel)
* If the wraparound failsafe has engaged -- either via the check
* above or during index vacuuming invoked from this loop -- stop
* using the buffer access strategy so that the rest of the vacuum may
* use all of shared buffers.
* use all of shared buffers. Failsafe mode stays engaged once
* triggered, so we only need to do this once.
*/
if (unlikely(VacuumFailsafeActive))
if (unlikely(VacuumFailsafeActive) && !strategy_cleared)
{
read_stream_clear_strategy(stream);
strategy_cleared = true;
}
buf = read_stream_next_buffer(stream, &per_buffer_data);