# PostgreSQL invalid indexes from failed CONCURRENTLY builds > Source-anchored research for PostgreSQL invalid indexes from failed CONCURRENTLY builds. Run status: COMPLETED. Parent: [Resumable index builds](https://llms-explorer.com/tree/resumable-index-builds/) · 4 facets · 9 facts · page: https://llms-explorer.com/tree/postgresql-invalid-indexes-from-failed-concurrently-builds/ ## Definitions - Inspect pg_index.indisvalid for query eligibility and indisready for INSERT/UPDATE maintenance; indisready=false means writes ignore the index, so invalid does not imply one universal maintenance state. (low confidence) — [source](https://www.postgresql.org/docs/current/catalog-pg-index.html) ## Problems, failure modes and limitations - Deadlocks or uniqueness errors during concurrent scanning can leave invalid indexes that queries cannot use; pganalyze independently documents failed or aborted concurrent builds as a typical cause. (high confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) - A unique concurrent build starts enforcing uniqueness during its second scan; failure there can leave uniqueness enforcement active even though queries cannot use the index. (medium confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) - Blind retries can fail with relation already exists; IF NOT EXISTS only checks name existence and cannot establish that the existing index is usable or matches the intended definition. (medium confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) - A running concurrent build is initially invalid too; indisvalid=false alone cannot establish that creation has failed. (medium confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) ## Comparisons and alternatives - Concurrent creation uses multiple transactions; cancellation after catalog creation can leave an INVALID index, unlike an aborted ordinary build. (medium confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) ## Facts and statements - Invalid artifacts can occupy disk and incur write maintenance despite providing no query acceleration; dbi demonstrates a sequential scan and subsequent index growth. (high confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) - Drop and recreate a failed index, or use REINDEX INDEX CONCURRENTLY; the latter is the REINDEX form that can concurrently rebuild an invalid index. (medium confidence) — [source](https://www.postgresql.org/docs/current/sql-createindex.html) - After failed concurrent reindexing, an INVALID _ccnew artifact represents the unfinished replacement; drop it and retry. An INVALID _ccold artifact is the old index left after successful rebuilding; drop it. Numeric suffixes may follow these names. (low confidence) — [source](https://www.postgresql.org/docs/current/sql-reindex.html)