How to Fix PostgreSQL ERROR 55006 (Catalog Cache Lookup Failed) in 2025
Quick Fix Summary
TL;DRRestart PostgreSQL with `pg_ctl restart -D /path/to/data` to forcibly clear the corrupted catalog cache.
PostgreSQL's catalog cache stores metadata about database objects. ERROR 55006 indicates this cache has become corrupted or desynchronized from the on-disk system catalogs, causing queries to fail.
Diagnosis & Causes
Recovery Steps
Step 1: Immediate Service Restart
A restart forces PostgreSQL to rebuild its catalog cache from disk. This is the fastest first step to restore service.
# As the postgres user or with sudo
pg_ctl restart -D /var/lib/postgresql/16/main
# Or using systemd
sudo systemctl restart postgresqlStep 2: Check for Underlying Corruption with pg_catalog Queries
If the restart fails or the error returns, probe the system catalogs directly for corruption.
psql -U postgres -c "SELECT COUNT(*) FROM pg_class;"
psql -U postgres -c "SELECT COUNT(*) FROM pg_attribute;"
psql -U postgres -c "SELECT COUNT(*) FROM pg_proc;"Step 3: Run a Full Database Cluster Check (pg_amcheck)
Use PostgreSQL's integrity checker to scan for physical and logical corruption in system catalogs.
# Install the amcheck extension if needed
psql -U postgres -c "CREATE EXTENSION IF NOT EXISTS amcheck;"
# Run a check on all databases
pg_amcheck --all -d postgresStep 4: Repair with REINDEX SYSTEM
If corruption is isolated to indexes, rebuilding all system catalog indexes can resolve the cache issue.
psql -U postgres
\connect postgres
REINDEX SYSTEM postgres;Step 5: Last Resort - Restore pg_catalog from a Known Good Backup
For severe corruption, you may need to restore the core `pg_*` system tables. This is complex and requires a recent base backup.
# 1. Stop PostgreSQL.
sudo systemctl stop postgresql
# 2. Move the corrupted data directory.
mv /var/lib/postgresql/16/main /var/lib/postgresql/16/main.corrupt
# 3. Extract pg_global/ and base/1/ from your physical backup.
# 4. Start PostgreSQL and run pg_upgrade if versions differ.Architect's Pro Tip
"Monitor for this error after major version upgrades or schema changes. It often surfaces when `pg_statistic` or `pg_depend` catalog entries are out of sync with their indexes."
Frequently Asked Questions
Does ERROR 55006 mean my user data is lost?
Not necessarily. The corruption is typically in the system metadata cache (catalog), not your actual table data. However, it prevents access until resolved.
Can I prevent ERROR 55006?
Ensure clean shutdowns, use reliable storage (EBS, SSD), avoid manual file edits in the data directory, and keep PostgreSQL patched to known stable versions.
How is this different from 'cache lookup failed for relation'?
ERROR 55006 is a generic cache failure code. The specific failed lookup (e.g., for relation, type, function) is in the accompanying error message, which dictates the repair focus.