From 82b45b2c1e19106af332e8f3a0fe0acde0d02bef Mon Sep 17 00:00:00 2001 From: Bharath Rupireddy Date: Sat, 4 Jul 2026 03:09:41 +0000 Subject: [PATCH] Fix pg_get_publication_tables race with concurrent DROP TABLE The pg_get_publication_tables() SRF collects the published table OIDs in its first call, and then reopens each table later, once per result row, to fetch its column list and row filter. For publications whose table set is gathered in bulk, namely FOR ALL TABLES and FOR TABLES IN SCHEMA, this reopen used table_open(), which errors out with "could not open relation with OID" if a table has been dropped in the meantime. This is common in environments where many tables are being created and dropped while publication tables are being queried. The bug was introduced by b7ae03953690 in PG16. This commit fixes it by using try_table_open(), which returns NULL instead of erroring out if the relation no longer exists. We now open all tables this way regardless of whether a column list is specified, so a concurrently dropped table is consistently skipped. Such tables are simply absent from the result set, which is the expected point-in-time behavior. To skip dropped tables without emitting a row, we track the current index into the table list ourselves rather than relying on funcctx->call_cntr. An isolation test exercises the race using a FOR TABLES IN SCHEMA publication. Author: Bharath Rupireddy Reviewed-by: Bertrand Drouvot Reviewed-by: shveta malik Reviewed-by: Ajin Cherian Reviewed-by: Masahiko Sawada 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 | 52 +++++++++++++++---- .../expected/pub-concurrent-drop.out | 16 ++++++ src/test/isolation/isolation_schedule | 1 + .../isolation/specs/pub-concurrent-drop.spec | 36 +++++++++++++ src/tools/pgindent/typedefs.list | 1 + 5 files changed, 97 insertions(+), 9 deletions(-) create mode 100644 src/test/isolation/expected/pub-concurrent-drop.out create mode 100644 src/test/isolation/specs/pub-concurrent-drop.spec diff --git a/src/backend/catalog/pg_publication.c b/src/backend/catalog/pg_publication.c index 0602398a545..0b21076dbc4 100644 --- a/src/backend/catalog/pg_publication.c +++ b/src/backend/catalog/pg_publication.c @@ -1052,14 +1052,27 @@ Datum pg_get_publication_tables(PG_FUNCTION_ARGS) { #define NUM_PUBLICATION_TABLES_ELEM 4 + + /* + * State carried across SRF calls. We track the index ourselves instead of + * using funcctx->call_cntr, so that concurrently dropped tables can be + * skipped without emitting a row. + */ + typedef struct + { + List *table_infos; /* list of published_rel */ + int curr_idx; /* current index into table_infos */ + } publication_tables_state; + FuncCallContext *funcctx; - List *table_infos = NIL; + publication_tables_state *ptstate = NULL; /* stuff done only on the first call of the function */ if (SRF_IS_FIRSTCALL()) { TupleDesc tupdesc; MemoryContext oldcontext; + List *table_infos = NIL; ArrayType *arr; Datum *elems; int nelems, @@ -1158,26 +1171,47 @@ pg_get_publication_tables(PG_FUNCTION_ARGS) PG_NODE_TREEOID, -1, 0); 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); + Relation rel; + Oid schemaid; Datum values[NUM_PUBLICATION_TABLES_ELEM] = {0}; bool nulls[NUM_PUBLICATION_TABLES_ELEM] = {0}; + /* Advance the index for the next call. */ + ptstate->curr_idx++; + + /* + * The table OIDs were collected earlier, so a table may have been + * dropped before we get here. try_table_open() returns NULL if it is + * already gone, in which case we skip it; such tables are simply + * absent from the result set, which is the expected point-in-time + * behavior. + */ + rel = try_table_open(relid, AccessShareLock); + if (rel == NULL) + continue; + /* * Form tuple with appropriate data. */ @@ -1191,6 +1225,7 @@ pg_get_publication_tables(PG_FUNCTION_ARGS) * We don't consider row filters or column lists for FOR ALL TABLES or * FOR TABLES IN SCHEMA publications. */ + schemaid = RelationGetNamespace(rel); if (!pub->alltables && !SearchSysCacheExists2(PUBLICATIONNAMESPACEMAP, ObjectIdGetDatum(schemaid), @@ -1220,7 +1255,6 @@ 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); int nattnums = 0; int16 *attnums; TupleDesc desc = RelationGetDescr(rel); @@ -1243,10 +1277,10 @@ pg_get_publication_tables(PG_FUNCTION_ARGS) values[2] = PointerGetDatum(buildint2vector(attnums, nattnums)); nulls[2] = false; } - - table_close(rel, AccessShareLock); } + table_close(rel, AccessShareLock); + rettuple = heap_form_tuple(funcctx->tuple_desc, values, nulls); SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(rettuple)); diff --git a/src/test/isolation/expected/pub-concurrent-drop.out b/src/test/isolation/expected/pub-concurrent-drop.out new file mode 100644 index 00000000000..8360af0ec9c --- /dev/null +++ b/src/test/isolation/expected/pub-concurrent-drop.out @@ -0,0 +1,16 @@ +Parsed test spec with 2 sessions + +starting permutation: lock list_pub_tables drop_and_commit +step lock: BEGIN; LOCK pubdrop.dropme IN ACCESS EXCLUSIVE MODE; +step list_pub_tables: + SELECT relid::regclass AS tablename + FROM pg_get_publication_tables('pub_schema') + ORDER BY tablename; + +step drop_and_commit: DROP TABLE pubdrop.dropme; COMMIT; +step list_pub_tables: <... completed> +tablename +-------------- +pubdrop.keepme +(1 row) + diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule index 7a4ab2ce805..06efed5279b 100644 --- a/src/test/isolation/isolation_schedule +++ b/src/test/isolation/isolation_schedule @@ -94,6 +94,7 @@ test: async-notify test: vacuum-no-cleanup-lock test: timeouts test: vacuum-concurrent-drop +test: pub-concurrent-drop test: vacuum-conflict test: vacuum-skip-locked test: stats diff --git a/src/test/isolation/specs/pub-concurrent-drop.spec b/src/test/isolation/specs/pub-concurrent-drop.spec new file mode 100644 index 00000000000..4f7d701d60c --- /dev/null +++ b/src/test/isolation/specs/pub-concurrent-drop.spec @@ -0,0 +1,36 @@ +# Tests for concurrently dropping a relation while a publication's tables are +# being listed. + +setup +{ + CREATE SCHEMA pubdrop; + CREATE PUBLICATION pub_schema FOR TABLES IN SCHEMA pubdrop; + CREATE TABLE pubdrop.dropme (id int); + CREATE TABLE pubdrop.keepme (id int); +} + +teardown +{ + DROP SCHEMA pubdrop CASCADE; + DROP PUBLICATION pub_schema; +} + +session s1 +step lock { BEGIN; LOCK pubdrop.dropme IN ACCESS EXCLUSIVE MODE; } +step drop_and_commit { DROP TABLE pubdrop.dropme; COMMIT; } + +session s2 +step list_pub_tables +{ + SELECT relid::regclass AS tablename + FROM pg_get_publication_tables('pub_schema') + ORDER BY tablename; +} + +# Hold an ACCESS EXCLUSIVE lock on the table in one session, so that the query +# listing a publication's tables in another session blocks when it tries to +# open the locked table. Then drop the table in the same lock-holding session +# and commit, releasing the lock, so the query in another session resumes and +# skips the now-dropped table instead of erroring with "could not open relation +# with OID". +permutation lock list_pub_tables drop_and_commit diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index e5634ae2969..86b194da8e3 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -3805,6 +3805,7 @@ 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