Cookbook recipe

Partial indexes for hot subsets of data

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

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Estimated investigation4 min

Scenario

Most rows are "done" but you constantly query the few "pending" ones. A partial index covers only the hot subset — smaller, faster, cheaper to maintain. Diagnose it Confirm the predicate is selective, then index only…

Investigation Path

Most rows are “done” but you constantly query the few “pending” ones. A partial index covers only the hot subset — smaller, faster, cheaper to maintain.

Diagnose it

Confirm the predicate is selective, then index only that slice:

CREATE INDEX idx_jobs_pending
  ON jobs (created_at)
  WHERE status = 'pending';

Why it happens

A full index on a low-cardinality flag wastes space and write effort on rows you never query by that flag. A partial index stores only matching rows, so it is tiny and stays in cache.

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