Cookbook recipe

Read the lock manager: pg_locks decoded

Applies to PostgreSQL 13–17 Last reviewed May 2026 Grounded in source

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A production experience capsule based on real incident patterns.

Why It Matters

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Estimated investigation4 min

Scenario

pg_locks is dense and cryptic. Learn to read it to understand exactly what each session holds and waits for. Diagnose it Join locks to activity for readable output: SELECT l.pid, l.locktype, l.mode, l.granted, left(a.query,50) FROM pg_locks…

Investigation Path

pg_locks is dense and cryptic. Learn to read it to understand exactly what each session holds and waits for.

Diagnose it

Join locks to activity for readable output:

SELECT l.pid, l.locktype, l.mode, l.granted, left(a.query,50)
FROM pg_locks l JOIN pg_stat_activity a USING (pid)
ORDER BY l.granted, l.pid;

Why it happens

Each row is a lock request: granted=false means a session is waiting. locktype (relation, tuple, transactionid) and mode (e.g. AccessShareLock, RowExclusiveLock, AccessExclusiveLock) tell you what kind of access is held or wanted.

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Related & next steps

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Concepts on this page

pg_locks Tuple Lock
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