mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-21 15:12:02 +00:00
43 lines
1.3 KiB
C++
43 lines
1.3 KiB
C++
#pragma once
|
|
|
|
#include <DataTypes/DataTypeCustom.h>
|
|
#include <AggregateFunctions/IAggregateFunction.h>
|
|
#include <Common/FieldVisitors.h>
|
|
|
|
#include <IO/ReadHelpers.h>
|
|
|
|
namespace DB
|
|
{
|
|
|
|
/** The type SimpleAggregateFunction(fct, type) is meant to be used in an AggregatingMergeTree. It behaves like a standard
|
|
* data type but when rows are merged, an aggregation function is applied.
|
|
*
|
|
* The aggregation function is limited to simple functions whose merge state is the final result:
|
|
* any, anyLast, min, max, sum
|
|
*
|
|
* Examples:
|
|
*
|
|
* SimpleAggregateFunction(sum, Nullable(Float64))
|
|
* SimpleAggregateFunction(anyLast, LowCardinality(Nullable(String)))
|
|
* SimpleAggregateFunction(anyLast, IPv4)
|
|
*
|
|
* Technically, a standard IDataType is instanciated and customized with IDataTypeCustomName and DataTypeCustomDesc.
|
|
*/
|
|
|
|
class DataTypeCustomSimpleAggregateFunction : public IDataTypeCustomName
|
|
{
|
|
private:
|
|
const AggregateFunctionPtr function;
|
|
const DataTypes argument_types;
|
|
const Array parameters;
|
|
|
|
public:
|
|
DataTypeCustomSimpleAggregateFunction(const AggregateFunctionPtr & function_, const DataTypes & argument_types_, const Array & parameters_)
|
|
: function(function_), argument_types(argument_types_), parameters(parameters_) {}
|
|
|
|
const AggregateFunctionPtr getFunction() const { return function; }
|
|
String getName() const override;
|
|
};
|
|
|
|
}
|