Cookbook recipe

Detect deadlocks and design them out

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.

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Estimated investigation4 min

Scenario

Transactions occasionally fail with "deadlock detected". PostgreSQL broke the cycle by killing one — your job is to stop the cycles forming. Diagnose it Read the deadlock detail in the server log: -- log shows: Process…

Investigation Path

Transactions occasionally fail with “deadlock detected”. PostgreSQL broke the cycle by killing one — your job is to stop the cycles forming.

Diagnose it

Read the deadlock detail in the server log:

-- log shows: Process A waits for ... ; Process B waits for ...
SHOW deadlock_timeout;

Why it happens

A deadlock happens when two transactions each hold a lock the other needs, in opposite order. The detector waits deadlock_timeout, finds the cycle, and aborts one transaction (SQLSTATE 40P01).

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Related & next steps

More like this

Table Bloat (Dead Tuples Accumulation) Diagnosing I/O stalls with pg_stat_io Autovacuum Freeze Triggering at Inopportune Time Slow Query / Sequential Scan on Large Table Failover runbook: promote a standby safely

Concepts on this page

Transaction Deadlock Lock
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