From 4cd9ef0f973600f63d3886674d8afa28574e94cc Mon Sep 17 00:00:00 2001 From: Andrew Dunstan Date: Sat, 15 Aug 2026 16:14:37 -0400 Subject: [PATCH] Fix heapam_relation_toast_am() to return the literal heap AM oid. heapam_relation_toast_am() returned rel->rd_rel->relam instead of the heap AM oid, assuming the two are always equal since only heap relations were expected to reach it. That breaks for a table AM that reuses this callback by copying heap's whole TableAmRoutine: rel->rd_rel->relam is then the AM's own oid, so NewRelationCreateToastTable() makes the TOAST table that AM too. Building its chunk_id/chunk_seq index then fails in heap_getnext(), which requires rd_tableam to be literally GetHeapamTableAmRoutine() -- "only heap AM is supported" for any table with a toastable column. Return the literal HEAP_TABLE_AM_OID instead: TOAST tables are always plain heap, which is what the function's own comment already said. Discovered while investigating a report from Zsolt Parragi. Backpatch-thru: 14 --- src/backend/access/heap/heapam_handler.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index bf87430cf01..6b3d5fc46c0 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -31,6 +31,7 @@ #include "access/xact.h" #include "catalog/catalog.h" #include "catalog/index.h" +#include "catalog/pg_am_d.h" #include "catalog/storage.h" #include "catalog/storage_xlog.h" #include "commands/progress.h" @@ -2048,12 +2049,22 @@ heapam_relation_needs_toast_table(Relation rel) } /* - * TOAST tables for heap relations are just heap relations. + * TOAST tables are always plain heap relations, regardless of the AM of + * the table they belong to. Return the literal heap AM oid rather than + * rel->rd_rel->relam: those are only the same value when rel is itself a + * genuine heap relation. A table AM that reuses this callback (e.g. by + * copying the whole heap TableAmRoutine and overriding only a handful of + * callbacks) is not itself heap, so returning rel->rd_rel->relam would + * create its TOAST table using that AM instead -- and storage-layer code + * that still calls heap_getnext() directly (see its comment) rejects any + * relation whose rd_tableam is not literally GetHeapamTableAmRoutine(), + * which fails as soon as anything scans that TOAST table, e.g. to build + * its chunk_id/chunk_seq index. */ static Oid heapam_relation_toast_am(Relation rel) { - return rel->rd_rel->relam; + return HEAP_TABLE_AM_OID; } -- 2.43.0