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51 lines
1.7 KiB
C++
51 lines
1.7 KiB
C++
#pragma once
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#include <DB/AggregateFunctions/IAggregateFunction.h>
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#include <DB/DataTypes/IDataType.h>
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#include <boost/iterator/transform_iterator.hpp>
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namespace DB
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{
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/** Creates an aggregate function by name.
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*/
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class AggregateFunctionFactory final
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{
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friend class StorageSystemFunctions;
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private:
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/// No std::function, for smaller object size and less indirection.
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using Creator = AggregateFunctionPtr(*)(const String & name, const DataTypes & argument_types);
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using AggregateFunctions = std::unordered_map<String, Creator>;
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public:
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AggregateFunctionFactory();
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AggregateFunctionPtr get(const String & name, const DataTypes & argument_types, int recursion_level = 0) const;
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AggregateFunctionPtr tryGet(const String & name, const DataTypes & argument_types) const;
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bool isAggregateFunctionName(const String & name, int recursion_level = 0) const;
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/// For compatibility with SQL, it's possible to specify that certain aggregate function name is case insensitive.
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enum CaseSensitiveness
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{
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CaseSensitive,
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CaseInsensitive
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};
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/// Register an aggregate function by its name.
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void registerFunction(const String & name, Creator creator, CaseSensitiveness case_sensitiveness = CaseSensitive);
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AggregateFunctionFactory(const AggregateFunctionFactory &) = delete;
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AggregateFunctionFactory & operator=(const AggregateFunctionFactory &) = delete;
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private:
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AggregateFunctionPtr getImpl(const String & name, const DataTypes & argument_types, int recursion_level) const;
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private:
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AggregateFunctions aggregate_functions;
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/// Case insensitive aggregate functions will be additionally added here with lowercased name.
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AggregateFunctions case_insensitive_aggregate_functions;
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};
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}
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