How to diagnose and fix the 53100 disk_full error code in Postgres.

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The 53100 disk_full error in PostgreSQL indicates that the disk is full and PostgreSQL cannot write to it. This error can occur during operations that require disk space, such as creating a table, inserting data, or running a transaction. To diagnose and fix this error, consider the following strategies:

Check Disk Space

First, check the available disk space on the server where your PostgreSQL database is running. You can use the df command on Unix-like systems:

df -h

This will show you the available disk space for each mounted filesystem. Look for the filesystem that contains your PostgreSQL data directory, which is typically located at /var/lib/postgresql/data in many installations.

Clean Up Disk Space

If you find that the disk is indeed full, you can free up space by:

  • Deleting unnecessary files from the disk.
  • Archiving old logs or data files and moving them to a different storage system.
  • Dropping unneeded tables or indexes in your PostgreSQL database:
  DROP TABLE unneeded_table;
  • Vacuuming your database to reclaim space from deleted rows:
  VACUUM FULL;

Note that VACUUM FULL can require as much space as the largest table, so ensure you have enough space before running it.

Increase Disk Size

If cleaning up disk space is not an option or a temporary fix, consider increasing the disk size. This could involve:

  • Adding a new disk to the machine and moving the PostgreSQL data directory there.
  • If using a virtual machine or cloud service, resizing the disk volume according to the service’s capabilities.

Manage Tablespaces

PostgreSQL allows you to create multiple tablespaces and place database objects in different physical locations. If you have multiple tablespaces on different disks, you can move objects to tablespaces with more available space:

ALTER TABLE large_table SET TABLESPACE new_tablespace;

Monitor Disk Usage

Implement monitoring and alerting based on disk usage metrics to get notified before the disk becomes full. This proactive approach can prevent the 53100 disk_full error from occurring.

Adjust PostgreSQL Settings

Some PostgreSQL settings can help manage disk space usage:

  • work_mem: Reducing this setting can lower the amount of disk space used for temporary files.
  • maintenance_work_mem: Lowering this setting can reduce the disk space used during maintenance operations like VACUUM, REINDEX, and CREATE INDEX.

However, be cautious with these settings, as setting them too low might affect the performance of your database.

Check for Large Transactions

A large transaction can fill up the disk space by creating a lot of WAL (Write-Ahead Logging) data. If possible, break large transactions into smaller ones to mitigate this issue.

By following these steps, you should be able to diagnose and resolve the 53100 disk_full error in PostgreSQL. Always make sure to have regular backups and avoid making significant changes to a production database without proper planning and testing. For more information on how to deal with disk space issues in PostgreSQL, you can refer to resources such as PostgreSQL Error Codes documentation or Metis Data’s guide on PostgreSQL 53100 error.

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