DataTypePtr FunctionArrayReduce::getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const
{
/// The first argument is a constant string with the name of the aggregate function
/// (possibly with parameters in parentheses, for example: "quantile(0.99)").
if (arguments.size() < 2)
throw Exception("Number of arguments for function " + getName() + " doesn't match: passed "
+ toString(arguments.size()) + ", should be at least 2.",
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
const ColumnConst * aggregate_function_name_column = checkAndGetColumnConst<ColumnString>(arguments[0].column.get());
if (!aggregate_function_name_column)
throw Exception("First argument for function " + getName() + " must be constant string: name of aggregate function.",
ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
DataTypes argument_types(arguments.size() - 1);
for (size_t i = 1, size = arguments.size(); i < size; ++i)
{
const DataTypeArray * arg = checkAndGetDataType<DataTypeArray>(arguments[i].type.get());
if (!arg)
throw Exception("Argument " + toString(i) + " for function " + getName() + " must be an array but it has type "
+ arguments[i].type->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
argument_types[i - 1] = arg->getNestedType();
}
if (!aggregate_function)
{
String aggregate_function_name_with_params = aggregate_function_name_column->getValue<String>();
if (aggregate_function_name_with_params.empty())
throw Exception("First argument for function " + getName() + " (name of aggregate function) cannot be empty.",
ErrorCodes::BAD_ARGUMENTS);
String aggregate_function_name;
Array params_row;
getAggregateFunctionNameAndParametersArray(aggregate_function_name_with_params,
aggregate_function_name, params_row, "function " + getName());
aggregate_function = AggregateFunctionFactory::instance().get(aggregate_function_name, argument_types, params_row);
}
return aggregate_function->getReturnType();
}
