mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-09-29 05:00:47 +00:00
61 lines
1007 B
C
61 lines
1007 B
C
|
#pragma once
|
||
|
|
||
|
#include <DB/IO/WriteHelpers.h>
|
||
|
#include <DB/IO/ReadHelpers.h>
|
||
|
|
||
|
#include <DB/DataTypes/DataTypesNumberVariable.h>
|
||
|
|
||
|
#include <DB/AggregateFunctions/INullaryAggregateFunction.h>
|
||
|
|
||
|
|
||
|
namespace DB
|
||
|
{
|
||
|
|
||
|
/// Просто считает, сколько раз её вызвали
|
||
|
class AggregateFunctionCount : public INullaryAggregateFunction
|
||
|
{
|
||
|
private:
|
||
|
UInt64 count;
|
||
|
|
||
|
public:
|
||
|
AggregateFunctionCount() : count(0) {}
|
||
|
|
||
|
String getName() const { return "count"; }
|
||
|
|
||
|
AggregateFunctionPtr cloneEmpty() const
|
||
|
{
|
||
|
return new AggregateFunctionCount;
|
||
|
}
|
||
|
|
||
|
DataTypePtr getReturnType() const
|
||
|
{
|
||
|
return new DataTypeVarUInt;
|
||
|
}
|
||
|
|
||
|
void addZero() { ++count; }
|
||
|
|
||
|
void merge(const IAggregateFunction & rhs)
|
||
|
{
|
||
|
count += static_cast<const AggregateFunctionCount &>(rhs).count;
|
||
|
}
|
||
|
|
||
|
void serialize(WriteBuffer & buf) const
|
||
|
{
|
||
|
writeVarUInt(count, buf);
|
||
|
}
|
||
|
|
||
|
void deserializeMerge(ReadBuffer & buf)
|
||
|
{
|
||
|
UInt64 tmp;
|
||
|
readVarUInt(tmp, buf);
|
||
|
count += tmp;
|
||
|
}
|
||
|
|
||
|
Field getResult() const
|
||
|
{
|
||
|
return count;
|
||
|
}
|
||
|
};
|
||
|
|
||
|
}
|