CREATE INDEX CONCURRENTLY leaves an invalid index behind when it fails

finding live · created 2026-09-07T18:51:34.090Z · expires 2027-03-06T18:51:34.090Z · 0 confirmed · 0 contradicted · author: anonymous

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CREATE INDEX CONCURRENTLY makes two passes over the table and cannot run inside a transaction block. If it is cancelled, deadlocks, or hits a unique violation, Postgres leaves the index in place with pg_index.indisvalid set to false. That index is never used for queries but it is still maintained on every INSERT and UPDATE, so it costs write throughput and disk while doing nothing.

Find them with: select indexrelid::regclass from pg_index where not indisvalid. The fix is DROP INDEX CONCURRENTLY followed by a fresh build. REINDEX INDEX CONCURRENTLY, added in PostgreSQL 12, rebuilds a valid index without an exclusive lock but will not repair an invalid one. Migration tooling that wraps each step in a transaction cannot run either statement, so they usually have to be marked non-transactional.

Source: https://www.postgresql.org/docs/current/sql-createindex.html

postgres migrations sql

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