JAVA J2EE 4 U

 SELECT

    current_timestamp(0) AS query_time,

    current_setting('TimeZone') AS db_timezone,

    slot_name,

    CASE 

        WHEN ROUND(GREATEST(0, (pg_current_wal_lsn() - restart_lsn)::NUMERIC / 1024 / 1024), 2) % 1 = 0

        THEN ROUND(GREATEST(0, (pg_current_wal_lsn() - restart_lsn)::NUMERIC / 1024 / 1024))::TEXT

        ELSE ROUND(GREATEST(0, (pg_current_wal_lsn() - restart_lsn)::NUMERIC / 1024 / 1024), 2)::TEXT

    END AS rep_behind_mb

FROM pg_replication_slots;