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102 lines
3.6 KiB
C++
102 lines
3.6 KiB
C++
#include <Functions/IFunctionImpl.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 <DataTypes/getLeastSupertype.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 ifNull which takes 2 arguments and returns
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/// the value of the 1st argument if it is not null. Otherwise it returns
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/// the value of the 2nd argument.
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class FunctionIfNull : public IFunction
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{
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public:
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static constexpr auto name = "ifNull";
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explicit FunctionIfNull(const Context & context_) : context(context_) {}
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static FunctionPtr create(const Context & context)
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{
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return std::make_shared<FunctionIfNull>(context);
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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 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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ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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if (arguments[0]->onlyNull())
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return arguments[1];
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if (!arguments[0]->isNullable())
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return arguments[0];
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return getLeastSupertype({removeNullable(arguments[0]), arguments[1]});
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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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/// Always null.
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if (block.getByPosition(arguments[0]).type->onlyNull())
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{
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block.getByPosition(result).column = block.getByPosition(arguments[1]).column;
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return;
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}
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/// Could not contain nulls, so nullIf makes no sense.
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if (!block.getByPosition(arguments[0]).type->isNullable())
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{
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block.getByPosition(result).column = block.getByPosition(arguments[0]).column;
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return;
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}
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/// ifNull(col1, col2) == if(isNotNull(col1), assumeNotNull(col1), col2)
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Block temp_block = block;
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size_t is_not_null_pos = temp_block.columns();
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temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
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size_t assume_not_null_pos = temp_block.columns();
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temp_block.insert({nullptr, removeNullable(block.getByPosition(arguments[0]).type), ""});
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auto is_not_null = FunctionFactory::instance().get("isNotNull", context)->build(
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{temp_block.getByPosition(arguments[0])});
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auto assume_not_null = FunctionFactory::instance().get("assumeNotNull", context)->build(
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{temp_block.getByPosition(arguments[0])});
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auto func_if = FunctionFactory::instance().get("if", context)->build(
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{temp_block.getByPosition(is_not_null_pos), temp_block.getByPosition(assume_not_null_pos), temp_block.getByPosition(arguments[1])});
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is_not_null->execute(temp_block, {arguments[0]}, is_not_null_pos, input_rows_count);
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assume_not_null->execute(temp_block, {arguments[0]}, assume_not_null_pos, input_rows_count);
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func_if->execute(temp_block, {is_not_null_pos, assume_not_null_pos, arguments[1]}, result, input_rows_count);
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block.getByPosition(result).column = std::move(temp_block.getByPosition(result).column);
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}
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private:
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const Context & context;
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};
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void registerFunctionIfNull(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionIfNull>(FunctionFactory::CaseInsensitive);
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}
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}
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