GetAggregateConstructor processes the specification of a single aggregate function.

GetAggregateOutputType returns the output type for the given aggregate function when applied on the given types.

GetWindowFunctionInfo returns windowFunc constructor and the return type when given fn is applied to given inputTypes.

MakeParamTypesAllocator creates a new ParamTypesAllocator with enough space to allocate slices of parameter types for all the given aggregate functions.

NeedHashAggregator returns whether the given aggregator spec requires hash aggregation.

ParamTypesAllocator is a helper struct for batching allocations of aggregate function parameter types.

AggregateConstructor is a function that creates an aggregate function.