Cookbook recipe

Kill a runaway query or connection safely

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

What This Is

A production experience capsule based on real incident patterns.

Why It Matters

Builds production judgment under pressure.

Next Step

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Estimated investigation4 min

Scenario

A query is pegging CPU or holding a lock. You need to cancel it — gently first, forcefully if needed. Diagnose it Find the offending backend: SELECT pid, now()-query_start AS runtime, state, left(query,80) FROM pg_stat_activity WHERE…

Investigation Path

A query is pegging CPU or holding a lock. You need to cancel it — gently first, forcefully if needed.

Diagnose it

Find the offending backend:

SELECT pid, now()-query_start AS runtime, state, left(query,80)
FROM pg_stat_activity
WHERE state <> 'idle' ORDER BY runtime DESC;

Why it happens

pg_cancel_backend cancels the current query but keeps the session. pg_terminate_backend kills the whole connection (rolls back its transaction). Prefer cancel first.

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Career Impact

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Related & next steps

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Concepts on this page

Transaction Lock
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