From 30d47ec8c6c78f46bcd7116b7effb6988b126e43 Mon Sep 17 00:00:00 2001 From: Noah Misch Date: Tue, 29 Oct 2024 09:39:55 -0700 Subject: Unpin buffer before inplace update waits for an XID to end. Commit a07e03fd8fa7daf4d1356f7cb501ffe784ea6257 changed inplace updates to wait for heap_update() commands like GRANT TABLE and GRANT DATABASE. By keeping the pin during that wait, a sequence of autovacuum workers and an uncommitted GRANT starved one foreground LockBufferForCleanup() for six minutes, on buildfarm member sarus. Prevent, at the cost of a bit of complexity. Back-patch to v12, like the earlier commit. That commit and heap_inplace_lock() have not yet appeared in any release. Discussion: https://postgr.es/m/20241026184936.ae.nmisch@google.com --- src/backend/access/index/genam.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) (limited to 'src/backend/access/index/genam.c') diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 69c36084321..60c61039d66 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -814,6 +814,7 @@ systable_inplace_update_begin(Relation relation, int retries = 0; SysScanDesc scan; HeapTuple oldtup; + BufferHeapTupleTableSlot *bslot; /* * For now, we don't allow parallel updates. Unlike a regular update, @@ -835,10 +836,9 @@ systable_inplace_update_begin(Relation relation, Assert(IsInplaceUpdateRelation(relation) || !IsSystemRelation(relation)); /* Loop for an exclusive-locked buffer of a non-updated tuple. */ - for (;;) + do { TupleTableSlot *slot; - BufferHeapTupleTableSlot *bslot; CHECK_FOR_INTERRUPTS(); @@ -864,11 +864,9 @@ systable_inplace_update_begin(Relation relation, slot = scan->slot; Assert(TTS_IS_BUFFERTUPLE(slot)); bslot = (BufferHeapTupleTableSlot *) slot; - if (heap_inplace_lock(scan->heap_rel, - bslot->base.tuple, bslot->buffer)) - break; - systable_endscan(scan); - }; + } while (!heap_inplace_lock(scan->heap_rel, + bslot->base.tuple, bslot->buffer, + (void (*) (void *)) systable_endscan, scan)); *oldtupcopy = heap_copytuple(oldtup); *state = scan; -- cgit v1.2.3