From 0d3b3a12357f65dc6ff0af54aabdaf88dbcd2a9b Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Thu, 9 Apr 2026 15:02:32 +0300 Subject: [PATCH v3] Explicitly forbid WAIT FOR inside functions and procedures Previously we were relying on snapshot-based check to detect such cases. However, it appears that when WAIT FOR is wrapped into a stored procedure it could pass this check causing an error elsewhere. This commit implments an explicit isTopLevel check to reject WAIT FOR when called from within a function or procedure. The isTopLevel check catches this case early with a clear error message, matching the pattern used by other utility commands like VACUUM and REINDEX. The snapshot check is retained for the remaining case: transactions with isolation level higher than READ COMMITTED. Also add a test for WAIT FOR LSN wrapped in a procedure, complementing the existing test that uses a function wrapper. Reported-by: Satyanarayana Narlapuram Discussion: https://postgr.es/m/CAHg%2BQDcN-n3NUqgRtj%3DBQb9fFQmH8-DeEROCr%3DPDbw_BBRKOYA%40mail.gmail.com Author: Satyanarayana Narlapuram Reviewed-by: Alexander Korotkov --- src/backend/commands/wait.c | 15 +++++++++++++-- src/backend/tcop/utility.c | 3 ++- src/include/commands/wait.h | 3 ++- src/test/recovery/t/049_wait_for_lsn.pl | 21 +++++++++++++++++++-- 4 files changed, 36 insertions(+), 6 deletions(-) diff --git a/src/backend/commands/wait.c b/src/backend/commands/wait.c index 85fcd463b4c..ec132e125a5 100644 --- a/src/backend/commands/wait.c +++ b/src/backend/commands/wait.c @@ -31,7 +31,8 @@ void -ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, DestReceiver *dest) +ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, bool isTopLevel, + DestReceiver *dest) { XLogRecPtr lsn; int64 timeout = 0; @@ -135,6 +136,16 @@ ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, DestReceiver *dest) } } + /* + * WAIT FOR must not run inside a function or procedure. Forbid this case + * upfront. + */ + if (!isTopLevel) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("%s cannot be executed from a function or procedure", + "WAIT FOR"))); + /* * We are going to wait for the LSN. We should first care that we don't * hold a snapshot and correspondingly our MyProc->xmin is invalid. @@ -161,7 +172,7 @@ ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, DestReceiver *dest) ereport(ERROR, errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("WAIT FOR must be called without an active or registered snapshot"), - errdetail("WAIT FOR cannot be executed from a function or procedure, nor within a transaction with an isolation level higher than READ COMMITTED.")); + errdetail("WAIT FOR cannot be executed within a transaction with an isolation level higher than READ COMMITTED.")); /* * As the result we should hold no snapshot, and correspondingly our xmin diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c index 1d34c19913e..73a56f1df1d 100644 --- a/src/backend/tcop/utility.c +++ b/src/backend/tcop/utility.c @@ -1062,7 +1062,8 @@ standard_ProcessUtility(PlannedStmt *pstmt, case T_WaitStmt: { - ExecWaitStmt(pstate, (WaitStmt *) parsetree, dest); + ExecWaitStmt(pstate, (WaitStmt *) parsetree, isTopLevel, + dest); } break; diff --git a/src/include/commands/wait.h b/src/include/commands/wait.h index 521a312908d..a563579695c 100644 --- a/src/include/commands/wait.h +++ b/src/include/commands/wait.h @@ -16,7 +16,8 @@ #include "parser/parse_node.h" #include "tcop/dest.h" -extern void ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, DestReceiver *dest); +extern void ExecWaitStmt(ParseState *pstate, WaitStmt *stmt, bool isTopLevel, + DestReceiver *dest); extern TupleDesc WaitStmtResultDesc(WaitStmt *stmt); #endif /* WAIT_H */ diff --git a/src/test/recovery/t/049_wait_for_lsn.pl b/src/test/recovery/t/049_wait_for_lsn.pl index bf61b8c47cf..e108301ccdb 100644 --- a/src/test/recovery/t/049_wait_for_lsn.pl +++ b/src/test/recovery/t/049_wait_for_lsn.pl @@ -215,10 +215,27 @@ $node_standby->psql( 'postgres', "SELECT pg_wal_replay_wait_wrap('${lsn3}');", stderr => \$stderr); -ok( $stderr =~ - /WAIT FOR must be called without an active or registered snapshot/, +ok($stderr =~ /WAIT FOR cannot be executed from a function or procedure/, "get an error when running within another function"); +$node_primary->safe_psql( + 'postgres', qq[ +CREATE PROCEDURE pg_wal_replay_wait_proc(target_lsn pg_lsn) AS \$\$ + BEGIN + EXECUTE format('WAIT FOR LSN %L;', target_lsn); + END +\$\$ +LANGUAGE plpgsql; +]); + +$node_primary->wait_for_catchup($node_standby); +$node_standby->psql( + 'postgres', + "CALL pg_wal_replay_wait_proc('${lsn3}');", + stderr => \$stderr); +ok($stderr =~ /WAIT FOR cannot be executed from a function or procedure/, + "get an error when running within a procedure"); + # 6. Check parameter validation error cases on standby before promotion my $test_lsn = $node_primary->safe_psql('postgres', "SELECT pg_current_wal_insert_lsn()"); -- 2.39.5 (Apple Git-154)