Solving MySQL Error 1038 – SQLSTATE: HY001 (ER_OUT_OF_SORTMEMORY): Increasing Server Sort Buffer Size

When working with large datasets or complex queries in MySQL, you might encounter Error 1038, which indicates that the server has run out of memory allocated for sorting operations. This error can cause queries to fail, bringing your data operations to a halt. Understanding the cause and knowing how to resolve it will help you maintain the performance and reliability of your MySQL server.

Understanding Error 1038 (ER_OUT_OF_SORTMEMORY)

MySQL Error 1038 occurs when the memory allocated for sorting (the sort buffer) is exhausted during a query operation that involves sorting, such as ORDER BY, GROUP BY, or certain joins. The sort buffer is a memory buffer that MySQL uses for sorting rows. If the buffer is too small to handle the sort operation, MySQL returns this error.

Diagnosing the Problem

  1. Check Current Sort Buffer Size: Determine the current value of the sort buffer size by executing:
SHOW VARIABLES LIKE 'sort_buffer_size';
  1. Assess Query Complexity: Review the query that caused the error. Complex queries or those that involve sorting large numbers of rows are more likely to exceed sort buffer limits.
  2. Server Load and Resources: Consider the overall load on the server and the available memory resources. If the server is under heavy load or has limited memory, you may encounter this error more frequently.

Fixing the Error

Increase Sort Buffer Size

To resolve this error, you may need to increase the sort buffer size. This can be done on a per-session basis or globally.

Per-Session Increase:
If you want to increase the sort buffer size for the current session only, use:

SET SESSION sort_buffer_size = desired_size;

Replace desired_size with the new size in bytes.

Global Increase:
To change the sort buffer size for all new connections, use:

SET GLOBAL sort_buffer_size = desired_size;

Again, replace desired_size with the new size in bytes.

Permanent Increase:
To make the change permanent, you need to edit the MySQL configuration file (my.cnf or my.ini depending on your system) and set the sort_buffer_size under the [mysqld] section:

sort_buffer_size = desired_size

After making this change, you must restart the MySQL server for the new setting to take effect.

Optimize Queries

Sometimes, optimizing the query can reduce the memory required for sorting. Consider indexing columns used in ORDER BY or GROUP BY clauses to improve efficiency.

Monitor Server Resources

Ensure that your server has enough memory to handle the increased buffer size, as setting it too high can lead to excessive memory consumption and other issues. Monitor your server’s performance and adjust the sort buffer size as needed.


MySQL Error 1038 is a memory-related error that can be resolved by increasing the sort buffer size or optimizing queries to reduce memory usage. Carefully adjusting the sort buffer size, either per session or globally, can help avoid this error. However, it’s important to balance memory allocation with server resources to prevent negative impacts on overall server performance. By following these steps, you can effectively manage sort memory issues and maintain the efficiency of your MySQL server.

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