Correct query to check streaming replication lag - Mailing list pgsql-general

Hello All,

Can anyone please tell me which of the following is the correct replication lag query to find streaming replication lag in seconds?

1. SELECT extract(seconds from (now() - pg_last_xact_replay_timestamp())) AS time_lag;

2. SELECT CASE WHEN pg_last_xlog_receive_location() = pg_last_xlog_replay_location() THEN 0 ELSE EXTRACT (EPOCH FROM now() - pg_last_xact_replay_timestamp()) END AS log_delay;