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56 lines
1.5 KiB
C++
56 lines
1.5 KiB
C++
#pragma once
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#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <Interpreters/Context.h>
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namespace DB
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{
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/// Base class for constant functions
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template<typename Derived, typename T, typename ColumnT>
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class FunctionConstantBase : public IFunction
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{
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public:
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template <typename U>
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explicit FunctionConstantBase(U && constant_value_, bool is_distributed_ = false)
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: constant_value(std::forward<U>(constant_value_)), is_distributed(is_distributed_)
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{
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}
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String getName() const override
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{
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return Derived::name;
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}
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size_t getNumberOfArguments() const override
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{
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return 0;
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}
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DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
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{
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return std::make_shared<ColumnT>();
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}
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bool isDeterministic() const override { return false; }
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bool isDeterministicInScopeOfQuery() const override { return true; }
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/// Some functions may return different values on different shards/replicas, so it's not constant for distributed query
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bool isSuitableForConstantFolding() const override { return !is_distributed; }
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bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
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ColumnPtr executeImpl(const ColumnsWithTypeAndName &, const DataTypePtr & result_type, size_t input_rows_count) const override
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{
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return result_type->createColumnConst(input_rows_count, constant_value);
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}
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private:
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const T constant_value;
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bool is_distributed;
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};
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}
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