mariadb-columnstore-engine/utils/udfsdk/docs/source/reference/UDAFMap.rst

UDAFMap

The UDAFMap is where we tell the system about our function. For Columnstore 1.2, you must manually place your function into this map.

• open mcsv1_udaf.cpp
• add your header to the #include list
• add a new line to the UDAFMap::getMap() function

#include "allnull.h"
#include "ssq.h"
#include "median.h"
#include "avg_mode.h"
UDAF_MAP& UDAFMap::getMap()
{
   if (fm.size() > 0)
   {
       return fm;
   }
   // first: function name
   // second: Function pointer
   // please use lower case for the function name. Because the names might be 
   // case-insensitive in MySQL depending on the setting. In such case, 
   // the function names passed to the interface is always in lower case.
   fm["allnull"] = new allnull();
   fm["ssq"] = new ssq();
   fm["median"] = new median();
   fm["avg_mode"] = new avg_mode();

   return fm;
}

An alternative method added for 1.2 is to put the following in your .cpp file. replace "median" with the name of your function:

class Add_median_ToUDAFMap
{
public:
    Add_median_ToUDAFMap()
    {
        UDAFMap::getMap()["median"] = new median();
    }
};

static Add_median_ToUDAFMap addToMap;

This defines an object whose constructor adds the entry to the UDAFMap. The static declaration instatiates an object at runtime, thus adding the entry at startup.