Скачать или смотреть Resolving the uncommitted xmin Error in PostgreSQL

Learn how to fix the `uncommitted xmin` error in PostgreSQL, and what happens if you disable autovacuum. Discover proactive solutions to prevent data corruption in your database.
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This video is based on the question https://stackoverflow.com/q/66046459/ asked by the user 'Suphisara Subsurit' ( https://stackoverflow.com/u/15145168/ ) and on the answer https://stackoverflow.com/a/66048362/ provided by the user 'Laurenz Albe' ( https://stackoverflow.com/u/6464308/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing the uncommitted xmin Error in PostgreSQL

If you're using PostgreSQL and have encountered the error stating that "uncommitted xmin from before xid cutoff needs to be frozen," you're not alone. This problem typically arises during the automatic vacuum process and can lead to significant issues if left unresolved. In this guide, we’ll delve into what this error means, the potential consequences of ignoring it, and how to effectively fix it.

Understanding the Error

The error originates from the automatic vacuum process trying to manage system catalogs, specifically the following tables:

pg_catalog.pg_largeobject

pg_catalog.pg_largeobject_metadata

What Causes This Error?

The error is indicative of a potential data corruption issue within your PostgreSQL database. When uncommitted transactions linger past a certain point (the transaction ID cutoff), PostgreSQL’s autovacuum can fail to process records effectively, which in turn hampers database transactions.

Why is This a Problem?

If you continue to receive these errors without intervention, you risk your database reaching a state referred to as transaction ID wraparound, which can cause your database to stop accepting transactions altogether. This is a situation that can lead to severe data loss and corruption.

The Solution: Steps to Resolve the Issue

Step 1: Create a New Database Cluster

To address the underlying corruption in your database, follow these steps:

Create a New Database Cluster: This cluster will serve as a clean environment to restore your data.

Use pg_dumpall to Dump the Corrupted Cluster: This PostgreSQL utility allows you to export your database into a single script file that can be restored later. It's an essential tool when dealing with corrupted databases.

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Restore the Dump into the New Cluster: After creating the new database cluster, use the following command:

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Remove the Old Cluster: Once you’ve confirmed that the new cluster is functioning properly and all data has been restored, you can safely remove the previous corrupted cluster.

Step 2: Update PostgreSQL

While addressing the error, it’s crucial to ensure that your PostgreSQL installation is up to date. You are currently using version 11.6, which is outdated. The latest version (as of this writing) is 11.10. Updates often include critical bug fixes and enhancements that could prevent similar issues in the future.

Step 3: Identify Underlying Causes

If the error persists, consider checking for:

Hardware Issues: Sometimes, the hardware may have underlying problems that can lead to data corruption.

Software Bugs: Consult the PostgreSQL documentation or community forums to see if similar issues have been identified in your version.

Conclusion

Addressing the uncommitted xmin error is critical to maintaining the integrity of your PostgreSQL database. By following the steps outlined in this guide, you can successfully resolve the issue, protect your data, and prevent future occurrences. Remember, staying updated with the latest software releases is just as important as resolving current errors.

Don't allow your database to head toward disaster—take action today!