v5-0001-PG16-Fix-pg_get_publication_tables-race-with-conc.txt

From 843e1aa3afb9a09bed1ffe2aaa9953fd6c2f88d1 Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Wed, 29 Apr 2026 05:25:56 +0000
Subject: [PATCH v5] PG16 - Fix pg_get_publication_tables race with concurrent
 DROP TABLE

pg_get_publication_tables() collects table OIDs without locks on
the first call, then opens each table on subsequent calls. If a
table is dropped in between, the function errors with
"could not open relation with OID". This is common in environments
where many tables are being created and dropped while
pg_publication_tables view is queried, such as with
FOR ALL TABLES publications.

The bug was introduced by b7ae03953690 in PG16.

Fix by skipping concurrently dropped tables instead of erroring
out. Tables created after the list is built are simply not present
in the result set, which is expected point-in-time behavior.

Author: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Reviewed-by: Ajin Cherian <itsajin@gmail.com>
Discussion: https://www.postgresql.org/message-id/CALj2ACVYYooWH-5tJ6cPKkU%2BmutVxwb_z4S%2BqAi-zdrFqxXE2Q%40mail.gmail.com
Backpatch-through: 16
---
 src/backend/catalog/pg_publication.c | 38 +++++++++++++++++++++++-----
 src/tools/pgindent/typedefs.list     |  1 +
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/backend/catalog/pg_publication.c b/src/backend/catalog/pg_publication.c
index c488b6370b6..e773308539b 100644
--- a/src/backend/catalog/pg_publication.c
+++ b/src/backend/catalog/pg_publication.c
@@ -56,6 +56,13 @@ typedef struct
 static void publication_translate_columns(Relation targetrel, List *columns,
 										  int *natts, AttrNumber **attrs);
 
+/* State for pg_get_publication_tables SRF */
+typedef struct
+{
+	List	   *table_infos;	/* list of published_rel */
+	int			curr_idx;		/* current index into table_infos */
+} publication_tables_state;
+
 /*
  * Check if relation can be in given publication and throws appropriate
  * error if not.
@@ -1058,7 +1065,7 @@ pg_get_publication_tables(PG_FUNCTION_ARGS)
 {
 #define NUM_PUBLICATION_TABLES_ELEM	4
 	FuncCallContext *funcctx;
-	List	   *table_infos = NIL;
+	publication_tables_state *ptstate;
 
 	/* stuff done only on the first call of the function */
 	if (SRF_IS_FIRSTCALL())
@@ -1066,6 +1073,7 @@ pg_get_publication_tables(PG_FUNCTION_ARGS)
 		TupleDesc	tupdesc;
 		MemoryContext oldcontext;
 		ArrayType  *arr;
+		List	   *table_infos = NIL;
 		Datum	   *elems;
 		int			nelems,
 					i;
@@ -1165,24 +1173,36 @@ pg_get_publication_tables(PG_FUNCTION_ARGS)
 		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 		funcctx->user_fctx = (void *) table_infos;
 
+		/* Store the state to be used across SRF calls. */
+		ptstate = palloc_object(publication_tables_state);
+		ptstate->table_infos = table_infos;
+		ptstate->curr_idx = 0;
+		funcctx->user_fctx = ptstate;
+
 		MemoryContextSwitchTo(oldcontext);
 	}
 
 	/* stuff done on every call of the function */
 	funcctx = SRF_PERCALL_SETUP();
-	table_infos = (List *) funcctx->user_fctx;
+	ptstate = (publication_tables_state *) funcctx->user_fctx;
 
-	if (funcctx->call_cntr < list_length(table_infos))
+	while (ptstate->curr_idx < list_length(ptstate->table_infos))
 	{
 		HeapTuple	pubtuple = NULL;
 		HeapTuple	rettuple;
 		Publication *pub;
-		published_rel *table_info = (published_rel *) list_nth(table_infos, funcctx->call_cntr);
+		published_rel *table_info = (published_rel *) list_nth(ptstate->table_infos, ptstate->curr_idx);
 		Oid			relid = table_info->relid;
 		Oid			schemaid = get_rel_namespace(relid);
 		Datum		values[NUM_PUBLICATION_TABLES_ELEM] = {0};
 		bool		nulls[NUM_PUBLICATION_TABLES_ELEM] = {0};
 
+		ptstate->curr_idx++;
+
+		/* Skip if the relation has been concurrently dropped. */
+		if (!OidIsValid(schemaid))
+			continue;
+
 		/*
 		 * Form tuple with appropriate data.
 		 */
@@ -1225,12 +1245,18 @@ pg_get_publication_tables(PG_FUNCTION_ARGS)
 		/* Show all columns when the column list is not specified. */
 		if (nulls[2])
 		{
-			Relation	rel = table_open(relid, AccessShareLock);
+			Relation	rel = try_table_open(relid, AccessShareLock);
 			int			nattnums = 0;
 			int16	   *attnums;
-			TupleDesc	desc = RelationGetDescr(rel);
+			TupleDesc	desc;
 			int			i;
 
+			/* Skip if the relation has been concurrently dropped. */
+			if (rel == NULL)
+				continue;
+
+			desc = RelationGetDescr(rel);
+
 			attnums = (int16 *) palloc(desc->natts * sizeof(int16));
 
 			for (i = 0; i < desc->natts; i++)
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index db43f32bcdd..8a93cc8dfc4 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -3652,6 +3652,7 @@ pthread_mutex_t
 pthread_once_t
 pthread_t
 ptrdiff_t
+publication_tables_state
 published_rel
 pull_var_clause_context
 pull_varattnos_context
-- 
2.47.3