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59 lines
1.8 KiB
C++
59 lines
1.8 KiB
C++
#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <DataTypes/DataTypeLowCardinality.h>
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#include <Columns/ColumnsNumber.h>
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#include <Columns/ColumnLowCardinality.h>
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#include <Common/typeid_cast.h>
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namespace DB
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{
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class FunctionToLowCardinality: public IFunction
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{
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public:
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static constexpr auto name = "toLowCardinality";
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static FunctionPtr create(const Context &) { return std::make_shared<FunctionToLowCardinality>(); }
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String getName() const override { return name; }
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size_t getNumberOfArguments() const override { return 1; }
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bool useDefaultImplementationForNulls() const override { return false; }
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bool useDefaultImplementationForConstants() const override { return true; }
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bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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if (arguments[0]->lowCardinality())
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return arguments[0];
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return std::make_shared<DataTypeLowCardinality>(arguments[0]);
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}
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t /*input_rows_count*/) override
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{
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auto arg_num = arguments[0];
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const auto & arg = block.getByPosition(arg_num);
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auto & res = block.getByPosition(result);
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if (arg.type->lowCardinality())
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res.column = arg.column;
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else
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{
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auto column = res.type->createColumn();
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typeid_cast<ColumnLowCardinality &>(*column).insertRangeFromFullColumn(*arg.column, 0, arg.column->size());
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res.column = std::move(column);
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}
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}
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};
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void registerFunctionToLowCardinality(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionToLowCardinality>();
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}
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}
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