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62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
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#include <Functions/IFunction.h>
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#include <Functions/FunctionHelpers.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <Core/ColumnNumbers.h>
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#include <Columns/ColumnNullable.h>
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namespace DB
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{
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/// Implements the function isNull which returns true if a value
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/// is null, false otherwise.
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class FunctionIsNull : public IFunction
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{
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public:
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static constexpr auto name = "isNull";
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static FunctionPtr create(const Context &)
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{
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return std::make_shared<FunctionIsNull>();
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}
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std::string getName() const override
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{
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return name;
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}
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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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DataTypePtr getReturnTypeImpl(const DataTypes &) const override
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{
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return std::make_shared<DataTypeUInt8>();
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}
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t) override
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{
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const ColumnWithTypeAndName & elem = block.getByPosition(arguments[0]);
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if (elem.column->isColumnNullable())
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{
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/// Merely return the embedded null map.
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block.getByPosition(result).column = static_cast<const ColumnNullable &>(*elem.column).getNullMapColumnPtr();
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}
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else
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{
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/// Since no element is nullable, return a zero-constant column representing
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/// a zero-filled null map.
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block.getByPosition(result).column = DataTypeUInt8().createColumnConst(elem.column->size(), UInt64(0));
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}
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}
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};
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void registerFunctionIsNull(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionIsNull>();
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}
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}
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