mcsv1_udaf Introduction
=======================

mcsv1_udaf is a C++ API for writing User Defined Aggregate Functions (UDAF) and User Defined Analytic Functions (UDAnF) for the MariaDB Columstore engine. 

In Columnstore 1.2, functions written using this API must be compiled into the udfsdk and udf_mysql libraries of the Columnstore code branch.

The API has a number of features. The general theme is, there is a class that represents the function, there is a context under which the function operates, and there is a data store for intermediate values.

The steps required to create a function are:

* Decide on a :ref:`memory allocation <memory_allocation>` scheme.
* Create a :ref:`header file <header_file>` for your function.
* Create a :ref:`source file <source_file>` for your function.
* Implement :ref:`mariadb udaf api <mariadb_udaf>` code.
* Add the function to :ref:`UDAFMap <udafmap>` in mcsv1_udaf.cpp
* Add the function to :ref:`CMakeLists.txt <cmakelists>` in ./utils/udfsdk
* :ref:`Compile udfsdk <compile>`.
* :ref:`Copy the compiled libraries <copylibs>` to the working directories.

In 1.2, Columnstore does not have a plugin framework, so the functions have to be compiled into the libraries that Columnstore already loads.