Show locks postgres
Active locks with blocking/blocked status and query
psql -U postgres -d mydb -c "SELECT pid, relation::regclass, mode, granted, left(query,60) FROM pg_locks l JOIN pg_stat_activity a USING(pid) WHERE relation IS NOT NULL ORDER BY granted;"
more postgres
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Find long-running queries
SELECT pid, now()-query_start AS dur, state, query FROM pg_stat_activity WHERE state='active' AND now()-query_start > interval '5 min' ORDER BY dur DESC;
Kill a stuck backend
SELECT pg_terminate_backend(<pid>); -- graceful first: SELECT pg_cancel_backend(<pid>);
Top queries by total time
SELECT query, calls, total_exec_time, mean_exec_time, rows FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 20;
EXPLAIN with buffers
EXPLAIN (ANALYZE, BUFFERS, VERBOSE) SELECT ... ; -- shared hit/read shows cache vs disk I/O
Blocking lock tree
SELECT pid, pg_blocking_pids(pid) AS blocked_by, wait_event_type, query FROM pg_stat_activity WHERE cardinality(pg_blocking_pids(pid)) > 0;