Remote Database SRE: Modern Reliability Engineering Applied to Your Entire Database Tier

Traces the root blocking transaction PID, executing query statement, and waiting lock types without taking shared locks.

-- Isolate root blocking PID and cascading locked transactions
SELECT blocked_locks.pid     AS blocked_pid,
       blocked_activity.usename  AS blocked_user,
       blocking_locks.pid    AS blocking_pid,
       blocking_activity.usename AS blocking_user,
       blocked_activity.query    AS blocked_statement,
       blocking_activity.query   AS blocking_statement
FROM pg_catalog.pg_locks blocked_locks
JOIN pg_catalog.pg_stat_activity blocked_activity
  ON blocked_activity.pid = blocked_locks.pid
JOIN pg_catalog.pg_locks blocking_locks
  ON blocking_locks.locktype = blocked_locks.locktype
 AND blocking_locks.database IS NOT DISTINCT FROM blocked_locks.database
 AND blocking_locks.relation IS NOT DISTINCT FROM blocked_locks.relation
 AND blocking_locks.pid != blocked_locks.pid
JOIN pg_catalog.pg_stat_activity blocking_activity
  ON blocking_activity.pid = blocking_locks.pid
WHERE NOT blocked_locks.granted;

Inspects active non-sleeping worker threads and maps InnoDB lock wait relationships between contending transactions.

-- 1. Inspect non-sleeping worker threads running > 5 seconds
SELECT id, user, host, db, command, time, state,
       LEFT(info, 120) AS running_query
FROM information_schema.processlist
WHERE command != 'Sleep' AND time > 5
ORDER BY time DESC LIMIT 10;

-- 2. Inspect InnoDB data lock waits and blocking transactions
SELECT r.trx_id waiting_trx, r.trx_mysql_thread_id waiting_thread,
       b.trx_id blocking_trx, b.trx_mysql_thread_id blocking_thread
FROM performance_schema.data_lock_waits w
JOIN performance_schema.data_locks r ON r.engine_lock_id = w.requesting_engine_lock_id
JOIN performance_schema.data_locks b ON b.engine_lock_id = w.blocking_engine_lock_id;