All Your GUCs in a Row: ignore_system_indexes

A deep dive into PostgreSQL's ignore_system_indexes GUC parameter — a rarely-used backend-context boolean that forces all internal catalog lookups to use sequential scans instead of indexes. It exists specifically to recover from system catalog index corruption, a scenario where normal REINDEX fails because it depends on the very indexes that are broken. The post covers how to invoke it (via PGOPTIONS="-P" or single-user mode with postgres --single -P), its limitations (TOAST indexes are not bypassed, catalog writes still use indexes, DDL should be avoided), behavioral side effects (trigger/rule firing order changes to physical row order), and the correct recovery sequence: single-user mode → REINDEX SYSTEM; → verify with amcheck's bt_index_check. Managed services without single-user mode have no equivalent escape hatch.

Source: https://postgr.es/p/9rP. 8 Sync News only summarizes and links out; content copyright belongs to the authors and original sources.