Cookbook recipe

Tune autovacuum cost-based delay

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

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Estimated investigation4 min

Scenario

Autovacuum runs but never finishes on big tables — it is throttled. Cost-based delay tuning lets it keep up without hammering I/O. Diagnose it Check the throttle settings: SHOW autovacuum_vacuum_cost_limit; SHOW autovacuum_vacuum_cost_delay; Why it happens Autovacuum…

Investigation Path

Autovacuum runs but never finishes on big tables — it is throttled. Cost-based delay tuning lets it keep up without hammering I/O.

Diagnose it

Check the throttle settings:

SHOW autovacuum_vacuum_cost_limit;
SHOW autovacuum_vacuum_cost_delay;

Why it happens

Autovacuum accumulates a “cost” as it reads/writes pages and sleeps for cost_delay when it exceeds cost_limit. Too-conservative defaults throttle it so hard it cannot keep pace with churn on large tables.

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Concepts on this page

Autovacuum
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