EXPLAIN ANALYZE a query

Show query plan with actual timings and buffer usage

psql -U myuser -d mydb -c 'EXPLAIN (ANALYZE, BUFFERS, FORMAT TEXT) SELECT * FROM orders WHERE status = $1;'

More postgres commands

Show slow queries (pg_stat_statements)

psql -U postgres -d mydb -c "SELECT round(total_exec_time::numeric,2) ms, calls, round((total_exec_time/calls)::numeric,2) avg_ms, query FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 10;"

Top 10 slowest queries by total execution time
Show active queries

psql -U postgres -c "SELECT pid, now()-query_start AS duration, state, left(query,80) FROM pg_stat_activity WHERE state <> 'idle' ORDER BY duration DESC;"

Running queries with duration and truncated SQL
Kill long-running query

psql -U postgres -c "SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE now()-query_start > interval '5 min' AND state = 'active';"

Terminate all queries running longer than 5 minutes
Show table sizes

psql -U myuser -d mydb -c "SELECT schemaname, tablename, pg_size_pretty(pg_total_relation_size(schemaname||'.'||tablename)) size FROM pg_tables ORDER BY pg_total_relation_size(schemaname||'.'||tablename) DESC LIMIT 20;"

Top 20 tables by total size including indexes and TOAST
Show index usage

psql -U myuser -d mydb -c "SELECT relname, indexrelname, idx_scan, idx_tup_read FROM pg_stat_user_indexes ORDER BY idx_scan DESC LIMIT 20;"

Which indexes are actually being used and how often