diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c index 723f513d8b..9b32941a76 100644 --- a/src/backend/replication/walreceiver.c +++ b/src/backend/replication/walreceiver.c @@ -1325,7 +1325,6 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS) state = WalRcv->walRcvState; receive_start_lsn = WalRcv->receiveStart; receive_start_tli = WalRcv->receiveStartTLI; - written_lsn = pg_atomic_read_u64(&WalRcv->writtenUpto); flushed_lsn = WalRcv->flushedUpto; received_tli = WalRcv->receivedTLI; last_send_time = WalRcv->lastMsgSendTime; @@ -1345,6 +1344,19 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS) if (pid == 0 || !ready_to_display) PG_RETURN_NULL(); + /* + * We reach here if WAL receiver is ready to display (i.e., + * ready_to_display == true). In this case we can ensure that the atomic + * variable "writtenUpto" has already been initialized by WAL receiver, so + * we can safely read it here. + * + * Read "writtenUpto" without holding a spinlock. So it may not be + * consistent with other WAL receiver's shared variables protected by a + * spinlock. This is OK because that variable is used only for + * informational purpose and should not be used for data integrity checks. + */ + written_lsn = pg_atomic_read_u64(&WalRcv->writtenUpto); + /* determine result type */ if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) elog(ERROR, "return type must be a row type"); diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out index 81bdacf59d..6d048e309c 100644 --- a/src/test/regress/expected/sysviews.out +++ b/src/test/regress/expected/sysviews.out @@ -83,6 +83,13 @@ select count(*) = 1 as ok from pg_stat_wal; t (1 row) +-- We expect no walreceiver running in this test +select count(*) = 0 as ok from pg_stat_wal_receiver; + ok +---- + t +(1 row) + -- This is to record the prevailing planner enable_foo settings during -- a regression test run. select name, setting from pg_settings where name like 'enable%'; diff --git a/src/test/regress/sql/sysviews.sql b/src/test/regress/sql/sysviews.sql index b9b875bc6a..dc8c9a3ac2 100644 --- a/src/test/regress/sql/sysviews.sql +++ b/src/test/regress/sql/sysviews.sql @@ -40,6 +40,9 @@ select count(*) >= 0 as ok from pg_prepared_xacts; -- There must be only one record select count(*) = 1 as ok from pg_stat_wal; +-- We expect no walreceiver running in this test +select count(*) = 0 as ok from pg_stat_wal_receiver; + -- This is to record the prevailing planner enable_foo settings during -- a regression test run. select name, setting from pg_settings where name like 'enable%';