AggregateFunctionFactory class

The AggregateFunctionFactory class specifies metadata information such as the argument and return types of your aggregate function. It also instantiates your AggregateFunction subclass. Your subclass must implement the following methods:

• getPrototype() - Defines the number of parameters and data types accepted by the function. There is a single parameter for aggregate functions.

• getIntermediateTypes() - Defines the intermediate variable(s) used by the function. These variables are used when combining the results of aggregate() calls.

• getReturnType() - Defines the type of the output column.

Your function may also implement getParameterType(), which defines the names and types of parameters that this function uses.

Vertica uses this data when you call the CREATE AGGREGATE FUNCTION SQL statement to add the function to the database catalog.

API

Aggregate functions are supported for C++ only.

The AggregateFunctionFactory API provides the following methods for extension by subclasses:

virtual AggregateFunction *
        createAggregateFunction ServerInterface &srvInterface)=0;

virtual void getPrototype(ServerInterface &srvInterface,
        ColumnTypes &argTypes, ColumnTypes &returnType)=0;

virtual void getIntermediateTypes(ServerInterface &srvInterface,
        const SizedColumnTypes &inputTypes, SizedColumnTypes &intermediateTypeMetaData)=0;

virtual void getReturnType(ServerInterface &srvInterface,
        const SizedColumnTypes &argTypes, SizedColumnTypes &returnType)=0;

virtual void getParameterType(ServerInterface &srvInterface,
        SizedColumnTypes &parameterTypes);