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110 lines
3.9 KiB
C++
110 lines
3.9 KiB
C++
#pragma once
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#include <DB/Functions/IFunction.h>
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#include <DB/DataTypes/IDataType.h>
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#include <DB/Core/ColumnNumbers.h>
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namespace DB
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{
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class Block;
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class Context;
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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 & context);
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std::string getName() const override;
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size_t getNumberOfArguments() const override { return 1; }
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bool hasSpecialSupportForNulls() const override;
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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};
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/// Implements the function isNotNull which returns true if a value
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/// is not null, false otherwise.
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class FunctionIsNotNull : public IFunction
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{
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public:
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static constexpr auto name = "isNotNull";
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static FunctionPtr create(const Context & context);
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std::string getName() const override;
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size_t getNumberOfArguments() const override { return 1; }
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bool hasSpecialSupportForNulls() const override;
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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};
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/// Implements the function coalesce which takes a set of arguments and
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/// returns the value of the leftmost non-null argument. If no such value is
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/// found, coalesce() returns NULL.
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class FunctionCoalesce : public IFunction
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{
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public:
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static constexpr auto name = "coalesce";
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static FunctionPtr create(const Context & context);
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std::string getName() const override;
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bool hasSpecialSupportForNulls() const override;
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bool isVariadic() const override { return true; }
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size_t getNumberOfArguments() const override { return 0; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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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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static FunctionPtr create(const Context & context);
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std::string getName() const override;
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size_t getNumberOfArguments() const override { return 2; }
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bool hasSpecialSupportForNulls() const override;
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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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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public:
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static constexpr auto name = "nullIf";
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static FunctionPtr create(const Context & context);
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std::string getName() const override;
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size_t getNumberOfArguments() const override { return 2; }
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bool hasSpecialSupportForNulls() const override;
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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};
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/// Implements the function assumeNotNull which takes 1 argument and works as follows:
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/// - if the argument is a nullable column, return its embedded column;
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/// - otherwise return the original argument.
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/// NOTE: assumeNotNull may not be called with the NULL value.
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class FunctionAssumeNotNull : public IFunction
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{
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public:
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static constexpr auto name = "assumeNotNull";
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static FunctionPtr create(const Context & context);
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std::string getName() const override;
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size_t getNumberOfArguments() const override { return 1; }
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bool hasSpecialSupportForNulls() const override;
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override;
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result) override;
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};
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}
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