24.3. Adding New Procedures to MySQL

In MySQL, you can define a procedure in C++ that can access and modify the data in a query before it is sent to the client. The modification can be done on a row-by-row or GROUP BY level.

We have created an example procedure to show you what can be done.

Additionally, we recommend that you take a look at mylua. With this you can use the LUA language to load a procedure at runtime into mysqld.

24.3.1. Procedure Analyse

analyse([max_elements,[max_memory]])

This procedure is defined in the sql/sql_analyse.cc. This examines the result from your query and returns an analysis of the results:

max_elements (default 256) is the maximum number of distinct values analyse does notice per column. This is used by analyse to check whether the optimal data type should be of type ENUM.
max_memory (default 8192) is the maximum amount of memory that analyse should allocate per column while trying to find all distinct values.

SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements,[max_memory]])

24.3.2. Writing a Procedure

For the moment, the only documentation for this is the source.

You can find all information about procedures by examining the following files:

sql/sql_analyse.cc
sql/procedure.h
sql/procedure.cc
sql/sql_select.cc