ER_UDF_ERROR is raised when a user-defined function (UDF) called by MySQL fails at runtime.
MySQL ER_UDF_ERROR occurs when a user-defined function crashes, returns an error, or cannot be found. Recompile or reinstall the UDF, verify permissions, and reload the shared library to resolve the issue.
ER_UDF_ERROR
MySQL raises ER_UDF_ERROR when the server cannot execute a user-defined function (UDF). The message template "%s UDF failed; %s" is filled with the function name and a system-level description of why it failed.
The condition appears in versions 5.7.21 and later whenever a SELECT, UPDATE, or trigger calls a faulty UDF. Because the server executes UDF code inside its process, failures can halt statements or even crash the instance, so rapid remediation is vital.
Most occurrences trace back to problems in the shared object that implements the UDF. Missing symbols, incompatible compiler flags, or unsatisfied library dependencies lead MySQL to abort execution and return ER_UDF_ERROR.
Logic bugs inside the UDF, such as dereferencing null pointers or dividing by zero, also propagate the error. Additionally, insufficient FILE privilege, incorrect plugin_dir settings, or SELinux/AppArmor blocks can prevent MySQL from loading the library.
First verify that the referenced .so or .dll file exists in plugin_dir and is readable by the mysqld user. Recompile the UDF with the exact server headers and matching architecture to remove symbol mismatches.
If the shared library was upgraded, run DROP FUNCTION udf_name; then CREATE FUNCTION udf_name RETURNS ... SONAME 'your_udf.so'; to refresh metadata. Ensure the executing account has FILE privilege and that any security modules permit mysqld to access the path.
On Linux, ldconfig updates can break library links. Re-run ldconfig or set LD_LIBRARY_PATH in the mysqld service file to point at required libs, then restart MySQL.
In Windows, copying the DLL to the wrong ProgramData folder yields ER_UDF_ERROR. Move the file to the folder returned by SHOW VARIABLES LIKE 'plugin_dir'; and restart the service.
Compile UDFs on the same OS, architecture, and MySQL build flags as the target server. Use static linking where practical to avoid external dependencies.
Maintain automated tests that call the UDF after upgrades. In Galaxy, store CREATE FUNCTION statements in version-controlled collections so teams can redeploy quickly if a node rebuild loses the library.
ER_CANT_OPEN_LIBRARY indicates MySQL could not locate the shared object at all. Verify path and permissions.
ER_FUNCTION_NOT_DEFINED appears when the metadata exists but the underlying file was deleted. Reinstall the library and run CREATE FUNCTION again.
The .so or .dll that implements the UDF is absent from plugin_dir or lacks read permission for mysqld.
The library was compiled against a different MySQL or glibc version, causing unresolved symbols at load time.
Segmentation faults, divide-by-zero, or other bugs in the C/C++ code abort execution and surface as ER_UDF_ERROR.
SELinux, AppArmor, or Windows Defender blocks mysqld from accessing or executing the library file.
Raised when MySQL cannot open the specified shared library file.
Occurs when metadata references a UDF that no longer exists in mysql.func or on disk.
Signifies failure during the init() phase of a UDF.
Yes. MySQL caches UDF binaries, so restarting ensures the new library is loaded.
Set the plugin_dir to an empty directory and restart. This prevents loading the library while preserving mysql.func entries.
If a replicated statement hits ER_UDF_ERROR on the replica, replication will stop. Fix the UDF and start slave to resume.
Galaxy stores CREATE FUNCTION scripts in collections, making it easy to redeploy or roll back UDFs after server rebuilds.
.avif)
.avif){kind=logo}
