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