From dae436ec2b72c01c0ee0f4d029281c2413768381 Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Mon, 12 Aug 2024 13:37:29 -0400 Subject: [PATCH v2] Fix creation of partition descriptor during concurrent detach+drop Author: Kuntal Ghosh Reviewed-by: Junwang Zhao Reviewed-by: Tender Wang Discussion: https://postgr.es/m/18559-b48286d2eacd9a4e@postgresql.org --- src/backend/partitioning/partdesc.c | 30 +++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/src/backend/partitioning/partdesc.c b/src/backend/partitioning/partdesc.c index c661a303bf..b4e0ed0e71 100644 --- a/src/backend/partitioning/partdesc.c +++ b/src/backend/partitioning/partdesc.c @@ -209,6 +209,10 @@ retry: * shared queue. We solve this problem by reading pg_class directly * for the desired tuple. * + * If the partition recently detached is also dropped, we get no tuple + * from the scan. In that case, we also retry, and next time through + * here, we don't see that partition anymore. + * * The other problem is that DETACH CONCURRENTLY is in the process of * removing a partition, which happens in two steps: first it marks it * as "detach pending", commits, then unsets relpartbound. If @@ -223,8 +227,6 @@ retry: Relation pg_class; SysScanDesc scan; ScanKeyData key[1]; - Datum datum; - bool isnull; pg_class = table_open(RelationRelationId, AccessShareLock); ScanKeyInit(&key[0], @@ -233,17 +235,29 @@ retry: ObjectIdGetDatum(inhrelid)); scan = systable_beginscan(pg_class, ClassOidIndexId, true, NULL, 1, key); + + /* + * We could get one tuple from the scan (the normal case), or zero + * tuples if the table has been dropped meanwhile. + */ tuple = systable_getnext(scan); - datum = heap_getattr(tuple, Anum_pg_class_relpartbound, - RelationGetDescr(pg_class), &isnull); - if (!isnull) - boundspec = stringToNode(TextDatumGetCString(datum)); + if (HeapTupleIsValid(tuple)) + { + Datum datum; + bool isnull; + + datum = heap_getattr(tuple, Anum_pg_class_relpartbound, + RelationGetDescr(pg_class), &isnull); + if (!isnull) + boundspec = stringToNode(TextDatumGetCString(datum)); + } systable_endscan(scan); table_close(pg_class, AccessShareLock); /* - * If we still don't get a relpartbound value, then it must be - * because of DETACH CONCURRENTLY. Restart from the top, as + * If we still don't get a relpartbound value (either because + * boundspec is null or because there was no tuple), then it must + * be because of DETACH CONCURRENTLY. Restart from the top, as * explained above. We only do this once, for two reasons: first, * only one DETACH CONCURRENTLY session could affect us at a time, * since each of them would have to wait for the snapshot under -- 2.39.2