MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
MySQL Replication is compatible with JavaScript stored programs, provided that the MLE component is installed on each and every server in the topology, due to the following issues:
A replica without the component installed accepts
CREATE FUNCTION and
CREATE PROCEDURE statements
containing JavaScript code from the source, but the replica
cannot execute the stored programs thus created.
A JavaScript stored program created on a server without the component installed is not checked for validity.
The following SQL statements cannot be executed successfully on a replica that does not have the component installed:
CREATE LIBRARY
DROP LIBRARY
A CREATE FUNCTION or CREATE
PROCEDURE statement which contains a
USING clause
On a server without the MLE component, each of the statements just shown is rejected with a syntax error.
This means that, when a CREATE FUNCTION or
CREATE PROCEDURE statement without
USING, and which contains invalid JavaScript
code, is executed on a server without the MLE component
installed, the statement succeeds, and thus is replicated. If
the replica has the MLE component installed, an error is raised
when the replica attempts to execute such a statement, leading
to a break in replication.
In addition, when CREATE LIBRARY,
DROP LIBRARY, CREATE FUNCTION ...
USING, or CREATE PROCEDURE ...
USING is executed on a server without the MLE
component installed, the statement is always rejected because
the server does not support the syntax.
For installing (or uninstalling) the MLE component on MySQL servers used in replication, it recommended that you stop replication, install (or uninstall) the component on every server in the topology, and only then allow replication to resume. Replicating between servers in a mixed setting (that is, in which some servers have the MLE component installed and some do not) is not supported for the reasons stated in the previous paragraph.
For more information about JavaScript stored programs in MySQL, see Section 27.3, “JavaScript Stored Programs”. For information about the MLE component, see Section 7.5.7, “Multilingual Engine Component (MLE)”.