Series Summary: This is Part 5 of a multi-part series on PostgreSQL autovacuum failures.

While the previous posts focused on multi-database clusters, single-database PostgreSQL setups aren’t immune. In this part, we explore a separate gotcha: a long-lived temp table can cause PostgreSQL to panic and shut down as the transaction ID (XID) approaches wraparound.

Gotcha #2: Temp Tables and XID Wraparound

If a temporary table persists for too long, it will never be vacuumed, because autovacuum can’t touch temp tables. Despite this, temp tables still accumulate transaction IDs. As the XID nears wraparound, PostgreSQL will force a shutdown to protect against data corruption.

This process may clean up the temp tables during restart, but by then, you’re experiencing unexpected downtime.

The Fix

Preventative hygiene and monitoring:

• Use DROP TABLE or ON COMMIT DROP to ensure temp tables are removed when no longer needed.
• Avoid leaving long-lived sessions running indefinitely.
• Implement monitoring that tracks XID age and temp table usage across your cluster.

Key Takeaways

• Always clean up temp tables:
  • DROP TABLE
  • CREATE TEMP TABLE ... ON COMMIT DROP
  • Recycle long-lived sessions
• Implement a comprehensive monitoring solution to catch these scenarios early.

Even a single lingering temp table can destabilize your cluster, whether you have one database or many. These preventive practices are essential for keeping your PostgreSQL environments stable, especially in production systems where uptime matters.

⬅️ Back: Part 4 – Debugging Limitations in RDS and Cloud Environments

➡️ Next: Part 6 – Autovacuum Failure Prevention and Monitoring Strategies (coming July 15th)

Need Help?

Command Prompt is the world’s oldest dedicated Postgres services and consulting company, offering expert support for performance optimization and troubleshooting. Contact us today.

Can't wait for the full series? Receive a link to download the full series as a white paper by submitting your contact information below.