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76 lines
2.3 KiB
C++
76 lines
2.3 KiB
C++
#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 <DataTypes/DataTypeNullable.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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namespace
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{
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/// Implements the function nullIf which takes 2 arguments and returns
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/// NULL if both arguments have the same value. Otherwise it returns the
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/// value of the first argument.
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class FunctionNullIf : public IFunction
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{
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private:
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ContextPtr context;
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public:
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static constexpr auto name = "nullIf";
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static FunctionPtr create(ContextPtr context)
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{
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return std::make_shared<FunctionNullIf>(context);
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}
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explicit FunctionNullIf(ContextPtr context_) : context(context_) {}
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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 2; }
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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 isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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return makeNullable(arguments[0]);
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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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/// nullIf(col1, col2) == if(col1 = col2, NULL, col1)
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auto equals_func = FunctionFactory::instance().get("equals", context)->build(arguments);
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auto eq_res = equals_func->execute(arguments, equals_func->getResultType(), input_rows_count, /* dry_run = */ false);
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ColumnsWithTypeAndName if_columns
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{
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{eq_res, equals_func->getResultType(), ""},
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{result_type->createColumnConstWithDefaultValue(input_rows_count), result_type, "NULL"},
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arguments[0],
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};
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auto func_if = FunctionFactory::instance().get("if", context)->build(if_columns);
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auto if_res = func_if->execute(if_columns, result_type, input_rows_count, /* dry_run = */ false);
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return makeNullable(if_res);
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}
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};
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}
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REGISTER_FUNCTION(NullIf)
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{
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factory.registerFunction<FunctionNullIf>({}, FunctionFactory::Case::Insensitive);
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}
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}
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