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131 lines
3.0 KiB
C++
131 lines
3.0 KiB
C++
#pragma once
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#include <city.h>
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#include <stats/UniquesHashSet.h>
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#include <DB/IO/WriteHelpers.h>
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#include <DB/IO/ReadHelpers.h>
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#include <DB/IO/WriteBufferFromString.h>
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#include <DB/DataTypes/DataTypesNumberFixed.h>
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#include <DB/DataTypes/DataTypeString.h>
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#include <DB/AggregateFunctions/IUnaryAggregateFunction.h>
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namespace DB
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{
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template <typename T> struct AggregateFunctionUniqTraits;
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template <> struct AggregateFunctionUniqTraits<UInt64>
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{
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static UInt64 hash(UInt64 x) { return x; }
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};
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template <> struct AggregateFunctionUniqTraits<Int64>
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{
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static UInt64 hash(Int64 x) { return x; }
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};
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template <> struct AggregateFunctionUniqTraits<Float64>
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{
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static UInt64 hash(Float64 x)
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{
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UInt64 res = 0;
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memcpy(reinterpret_cast<char *>(&res), reinterpret_cast<char *>(&x), sizeof(x));
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return res;
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}
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};
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template <> struct AggregateFunctionUniqTraits<String>
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{
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/// Имейте ввиду, что вычисление приближённое.
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static UInt64 hash(const String & x) { return CityHash64(x.data(), x.size()); }
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};
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struct AggregateFunctionUniqData
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{
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UniquesHashSet set;
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};
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/// Приближённо вычисляет количество различных значений.
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template <typename T>
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class AggregateFunctionUniq : public IUnaryAggregateFunction<AggregateFunctionUniqData>
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{
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public:
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AggregateFunctionUniq() {}
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String getName() const { return "uniq"; }
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String getTypeID() const { return "uniq_" + TypeName<T>::get(); }
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DataTypePtr getReturnType() const
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{
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return new DataTypeUInt64;
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}
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void setArgument(const DataTypePtr & argument)
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{
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}
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void addOne(AggregateDataPtr place, const Field & value) const
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{
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data(place).set.insert(AggregateFunctionUniqTraits<T>::hash(get<const T &>(value)));
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}
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void merge(AggregateDataPtr place, ConstAggregateDataPtr rhs) const
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{
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data(place).set.merge(data(rhs).set);
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}
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void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const
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{
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data(place).set.write(buf);
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}
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void deserializeMerge(AggregateDataPtr place, ReadBuffer & buf) const
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{
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UniquesHashSet tmp_set;
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tmp_set.read(buf);
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data(place).set.merge(tmp_set);
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}
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Field getResult(ConstAggregateDataPtr place) const
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{
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return data(place).set.size();
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}
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};
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/** То же самое, но выводит состояние вычислений в строке в текстовом виде.
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* Используется, если какой-то внешней программе (сейчас это ███████████)
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* надо получить это состояние и потом использовать по-своему.
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*/
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template <typename T>
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class AggregateFunctionUniqState : public AggregateFunctionUniq<T>
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{
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public:
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String getName() const { return "uniqState"; }
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String getTypeID() const { return "uniqState_" + TypeName<T>::get(); }
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DataTypePtr getReturnType() const
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{
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return new DataTypeString;
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}
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Field getResult(ConstAggregateDataPtr place) const
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{
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Field res = String();
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WriteBufferFromString wb(get<String &>(res));
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this->data(place).set.writeText(wb);
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return res;
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}
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};
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}
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