PostgreSQL Buffer Cache Hit Ratio
Computes the shared buffer hit ratio per database. Shows whether memory is undersized and whether too much data is read from disk.
SELECT datname, blks_hit, blks_read,
round(100.0 * blks_hit / NULLIF(blks_hit + blks_read, 0), 2) AS hit_pct
FROM pg_stat_database
WHERE datname IS NOT NULL
ORDER BY blks_read DESC;Expected to be above 99% in OLTP systems. Since the OS page cache also operates beneath PostgreSQL, interpret alongside `pg_stat_io` (PG 16+).
- This script is designed for read-only diagnostics; it does not alter schema or modify data directly.
- Prior to executing on production systems under high load, verify the target database version (Min. Version: 9.x).
- Exercise caution with mutating actions (e.g., terminating sessions or dropping indexes) referenced in the notes section.
Other POSTGRESQL Diagnostic Scripts
View All (100)Find Long-Running Queries and Idle-in-Transaction Sessions in PostgreSQL
Lists queries running longer than a minute, their wait events, and idle-in-transaction sessions that block vacuum. The first script to run during a performance incident.
PostgreSQL Lock Chain: Who Is Blocking Whom?
Uses pg_blocking_pids to pair blocked and blocking sessions with their queries and wait times. Shows the root cause of a lock chain in seconds.
PostgreSQL Dead Tuples, Bloat and Autovacuum Health Check
Shows dead tuple ratio and last vacuum/analyze times per table. Helps you find tables where autovacuum settings are not keeping up.
Find Unused Indexes in PostgreSQL
Lists never-scanned indexes that are neither unique nor primary keys, with their sizes. Surfaces cleanup candidates to cut write overhead and disk usage.