UDAF/UDSF Module Definition - Aster Execution Engine

A typical module definition is as follows:

/*
* SQL-MR function module definition
*/
SQLMR_FUNCTION_MODULE_BEGIN()
{
   SQLMR_FUNCTION_ENTRY("average")
   {
      entry->newAggregatorFunction =
      &average_newAggregator;
   }
}
SQLMR_FUNCTION_MODULE_END()

The string given to SQLMR_FUNCTION_ENTRY is the name of the function. Within the module definition block, assign the function pointer of the factory method (for example, &average_newAggregator in the example above) to the respective one of the following members of SqlmrFunctionEntry according to the type of your function.

• For a scalar function:

  SqlmrErrorH (*newScalarFunction)(
     SqlmrTaskContextH taskContext,
     SqlmrRuntimeContractH contract,
     UdfScalarFunctionPointers* outPointers
  ) SQLMR_ERROR_RESULT;

• For an aggregate function:

  SqlmrErrorH (*newAggregatorFunction)(
     SqlmrTaskContextH taskContext,
     SqlmrRuntimeContractH contract,
     UdfAggregatorFunctionPointers* outPointers
  ) SQLMR_ERROR_RESULT;

• For a decomposable aggregate function:

  SqlmrErrorH (*newDecomposableAggregatorFunction)(
     SqlmrTaskContextH taskContext,
     SqlmrRuntimeContractH contract,
     UdfDecomposableAggregatorFunctionPointers* outPointers
  ) SQLMR_ERROR_RESULT;

It is good practice to also provide HelpInfo in the module definition. See HelpInfo for User Defined Functions.