Solving MySQL Error 1123 (ER_CANT_INITIALIZE_UDF): A Guide to Function Initialization Issues

Encountering Error 1123 – SQLSTATE: HY000 (ER_CANT_INITIALIZE_UDF) in MySQL indicates a problem initializing a User-Defined Function (UDF). The error message Can't initialize function '%s'; %s suggests that MySQL is unable to start a particular UDF due to a specific reason provided in the error message. Let’s explore various scenarios that can lead to this error and how to resolve them.

Understanding the Error

A UDF is a custom function written in a language outside of MySQL, typically C or C++, and compiled as a shared library. MySQL uses UDFs to extend its capabilities. Error 1123 can occur due to several reasons:

  • The UDF shared library file might not be in the expected directory.
  • The shared library file could lack execution permissions.
  • There might be issues within the UDF code itself, such as missing symbols or incorrect function signatures.
  • The UDF might be incompatible with the current version of MySQL.
  • Required dependencies for the UDF shared library could be missing.

Diagnosing the Issue

To diagnose the issue, you will need to:

  1. Check the MySQL error log for detailed information about the error.
  2. Verify the location and permissions of the UDF shared library.
  3. Ensure that the UDF is compatible with your MySQL version and properly compiled.
  4. Confirm that any dependencies required by the UDF are installed on the system.

Example Scenarios and Fixes

Scenario 1: Incorrect Library File Location

Problem: The UDF library file is not in the MySQL plugin directory.

-- Error 1123 occurs if '' is not in the plugin directory

Fix: Move the UDF shared library to the MySQL plugin directory, which can be found by executing:


Then, ensure the file is in the specified directory.

Scenario 2: Insufficient File Permissions

Problem: The UDF library file does not have the necessary execution permissions.

-rw-r--r-- 1 root root

Fix: Change the file permissions to allow execution.

chmod +x

Scenario 3: UDF Code Issues

Problem: The UDF code has issues, such as missing or mismatched function signatures.
Fix: Review the UDF code for correctness, recompile the UDF, and ensure that the function signatures match what MySQL expects.

Scenario 4: Incompatibility with MySQL Version

Problem: The UDF was compiled for a different version of MySQL and is not compatible with the current version.
Fix: Recompile the UDF against the correct version of MySQL that you are currently running.

Scenario 5: Missing Dependencies

Problem: The UDF depends on other libraries that are not installed on the system.
Fix: Identify the missing dependencies and install them. Use tools like ldd on Linux to check for shared library dependencies.

Scenario 6: Syntax Error in Function Creation

Problem: There is a syntax error in the CREATE FUNCTION statement.


Fix: Ensure that the syntax matches the expected format and that all required arguments are provided.


When facing Error 1123 in MySQL, it’s essential to systematically check the UDF library file’s location, permissions, and dependencies, as well as the UDF code and compatibility with MySQL. By addressing these areas, you can resolve initialization issues and successfully use your custom functions within MySQL.

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