-- Blocking: Queries holding locks that other queries are waiting on
-- Identifies lock contention causing query delays
-- Source: Crunchy Bridge CLI (heroku-pg-extras)

SELECT
  bl.pid AS blocked_pid,
  ka.query AS blocking_statement,
  now() - ka.query_start AS blocking_duration,
  kl.pid AS blocking_pid,
  a.query AS blocked_statement,
  now() - a.query_start AS blocked_duration
FROM pg_catalog.pg_locks bl
JOIN pg_catalog.pg_stat_activity a
  ON bl.pid = a.pid
JOIN pg_catalog.pg_locks kl
  JOIN pg_catalog.pg_stat_activity ka
    ON kl.pid = ka.pid
ON bl.transactionid = kl.transactionid AND bl.pid != kl.pid
WHERE NOT bl.granted;
