CLUSTER operation blocks all reads during reordering
criticalavailabilityUpdated Mar 4, 2026
Technologies:
How to detect:
The CLUSTER command takes exclusive locks that block even read queries while physically reordering table data.
Recommended action:
Use pg_repack or pg_squeeze extensions instead of CLUSTER for production systems, as they provide equivalent reordering functionality with uptime-friendly locking that doesn't block reads.