16 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 row by row or GROUP BY level.

We have created an example procedure in MySQL 3.23 to show you what can be done.

16.1 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 will notice per column. This is used by analyse to check if the optimal column type should be of type ENUM.
• max memory (default 8192) is the maximum memory analyse should allocate per column while trying to find all distinct values.

SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max elements,[max memory]])

16.2 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'

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