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136 lines
4.3 KiB
C++
136 lines
4.3 KiB
C++
#pragma once
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#include <DataTypes/getLeastSupertype.h>
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#include <DataTypes/NumberTraits.h>
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#include <Interpreters/castColumn.h>
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#include <Columns/ColumnsNumber.h>
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#include <Functions/IFunctionImpl.h>
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#include <Functions/FunctionFactory.h>
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#include <ext/map.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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}
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enum class LeastGreatest
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{
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Least,
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Greatest
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};
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template <LeastGreatest kind>
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class FunctionLeastGreatestGeneric : public IFunction
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{
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public:
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static constexpr auto name = kind == LeastGreatest::Least ? "least" : "greatest";
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static FunctionPtr create(const Context &) { return std::make_shared<FunctionLeastGreatestGeneric<kind>>(); }
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private:
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String getName() const override { return name; }
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size_t getNumberOfArguments() const override { return 0; }
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bool isVariadic() const override { return true; }
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bool useDefaultImplementationForConstants() const override { return true; }
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DataTypePtr getReturnTypeImpl(const DataTypes & types) const override
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{
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if (types.empty())
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throw Exception("Function " + getName() + " cannot be called without arguments", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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return getLeastSupertype(types);
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}
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ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
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{
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size_t num_arguments = arguments.size();
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if (1 == num_arguments)
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return arguments[0].column;
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Columns converted_columns(num_arguments);
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for (size_t arg = 0; arg < num_arguments; ++arg)
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converted_columns[arg] = castColumn(arguments[arg], result_type)->convertToFullColumnIfConst();
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auto result_column = result_type->createColumn();
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result_column->reserve(input_rows_count);
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for (size_t row_num = 0; row_num < input_rows_count; ++row_num)
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{
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size_t best_arg = 0;
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for (size_t arg = 1; arg < num_arguments; ++arg)
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{
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auto cmp_result = converted_columns[arg]->compareAt(row_num, row_num, *converted_columns[best_arg], 1);
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if constexpr (kind == LeastGreatest::Least)
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{
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if (cmp_result < 0)
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best_arg = arg;
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}
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else
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{
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if (cmp_result > 0)
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best_arg = arg;
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}
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}
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result_column->insertFrom(*converted_columns[best_arg], row_num);
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}
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return result_column;
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}
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};
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template <LeastGreatest kind, typename SpecializedFunction>
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class LeastGreatestOverloadResolver : public IFunctionOverloadResolverImpl
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{
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public:
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static constexpr auto name = kind == LeastGreatest::Least ? "least" : "greatest";
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static FunctionOverloadResolverImplPtr create(const Context & context)
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{
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return std::make_unique<LeastGreatestOverloadResolver<kind, SpecializedFunction>>(context);
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}
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explicit LeastGreatestOverloadResolver(const Context & context_) : context(context_) {}
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String getName() const override { return name; }
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size_t getNumberOfArguments() const override { return 0; }
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bool isVariadic() const override { return true; }
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FunctionBaseImplPtr build(const ColumnsWithTypeAndName & arguments, const DataTypePtr & return_type) const override
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{
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DataTypes argument_types;
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/// More efficient specialization for two numeric arguments.
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if (arguments.size() == 2 && isNumber(arguments[0].type) && isNumber(arguments[1].type))
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return std::make_unique<DefaultFunction>(SpecializedFunction::create(context), argument_types, return_type);
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return std::make_unique<DefaultFunction>(
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FunctionLeastGreatestGeneric<kind>::create(context), argument_types, return_type);
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}
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DataTypePtr getReturnType(const DataTypes & types) const override
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{
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if (types.empty())
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throw Exception("Function " + getName() + " cannot be called without arguments", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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if (types.size() == 2 && isNumber(types[0]) && isNumber(types[1]))
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return SpecializedFunction::create(context)->getReturnTypeImpl(types);
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return getLeastSupertype(types);
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}
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private:
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const Context & context;
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};
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}
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