EXPLAIN с буферами postgres
Выполнить запрос с реальными таймингами и попаданиями в буферы, чтобы увидеть дисковый I/O
EXPLAIN (ANALYZE, BUFFERS, VERBOSE) SELECT ... ; -- shared hit/read shows cache vs disk I/O
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Дерево блокировок
SELECT pid, pg_blocking_pids(pid) AS blocked_by, wait_event_type, query FROM pg_stat_activity WHERE cardinality(pg_blocking_pids(pid)) > 0;
Лаг репликации в байтах
SELECT client_addr, state, pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn) AS replay_lag_bytes, write_lag, flush_lag, replay_lag FROM pg_stat_replication;
Самые большие базы
SELECT datname, pg_size_pretty(pg_database_size(datname)) AS size FROM pg_database ORDER BY pg_database_size(datname) DESC;
Размер таблиц и индексов
SELECT relname, pg_size_pretty(pg_total_relation_size(oid)) AS total, pg_size_pretty(pg_relation_size(oid)) AS table FROM pg_class WHERE relkind='r' ORDER BY pg_total_relation_size(oid) DESC LIMIT 20;
Поиск неиспользуемых индексов
SELECT relname, indexrelname, idx_scan, pg_size_pretty(pg_relation_size(indexrelid)) AS size FROM pg_stat_user_indexes WHERE idx_scan=0 ORDER BY pg_relation_size(indexrelid) DESC;