ClickHouse/dbms/Functions/IFunctionImpl.h
Ivan 97f2a2213e
Move all folders inside /dbms one level up (#9974)
* Move some code outside dbms/src folder
* Fix paths
2020-04-02 02:51:21 +03:00

329 lines
15 KiB
C++

#pragma once
#include <Functions/IFunction.h>
/// This file contains developer interface for functions.
/// In order to implement a new function you can choose one of two options:
/// * Implement interface for IFunction (old function interface, which is planned to be removed sometimes)
/// * Implement three interfaces for IExecutableFunctionImpl, IFunctionBaseImpl and IFunctionOverloadResolverImpl
/// Generally saying, IFunction represents a union of tree new interfaces. However, it can't be used for all cases.
/// Examples:
/// * Function properties may depend on arguments type (e.g. toUInt32(UInt8) is globally monotonic, toUInt32(UInt64) - only on intervals)
/// * In implementation of lambda functions DataTypeFunction needs an functional object with known arguments and return type
/// * Function CAST prepares specific implementation based on argument types
///
/// Interfaces for IFunction, IExecutableFunctionImpl, IFunctionBaseImpl and IFunctionOverloadResolverImpl are pure.
/// Default implementations are in adaptors classes (IFunctionAdaptors.h), which are implement user interfaces via developer ones.
/// Interfaces IExecutableFunctionImpl, IFunctionBaseImpl and IFunctionOverloadResolverImpl are implemented via IFunction
/// in DefaultExecutable, DefaultFunction and DefaultOverloadResolver classes (IFunctionAdaptors.h).
namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int NOT_IMPLEMENTED;
}
/// Cache for functions result if it was executed on low cardinality column.
class ExecutableFunctionLowCardinalityResultCache;
using ExecutableFunctionLowCardinalityResultCachePtr = std::shared_ptr<ExecutableFunctionLowCardinalityResultCache>;
class IExecutableFunctionImpl
{
public:
virtual ~IExecutableFunctionImpl() = default;
virtual String getName() const = 0;
virtual void execute(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) = 0;
virtual void executeDryRun(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count)
{
execute(block, arguments, result, input_rows_count);
}
/** Default implementation in presence of Nullable arguments or NULL constants as arguments is the following:
* if some of arguments are NULL constants then return NULL constant,
* if some of arguments are Nullable, then execute function as usual for block,
* where Nullable columns are substituted with nested columns (they have arbitrary values in rows corresponding to NULL value)
* and wrap result in Nullable column where NULLs are in all rows where any of arguments are NULL.
*/
virtual bool useDefaultImplementationForNulls() const { return true; }
/** If the function have non-zero number of arguments,
* and if all arguments are constant, that we could automatically provide default implementation:
* arguments are converted to ordinary columns with single value, then function is executed as usual,
* and then the result is converted to constant column.
*/
virtual bool useDefaultImplementationForConstants() const { return false; }
/** If function arguments has single low cardinality column and all other arguments are constants, call function on nested column.
* Otherwise, convert all low cardinality columns to ordinary columns.
* Returns ColumnLowCardinality if at least one argument is ColumnLowCardinality.
*/
virtual bool useDefaultImplementationForLowCardinalityColumns() const { return true; }
/** Some arguments could remain constant during this implementation.
*/
virtual ColumnNumbers getArgumentsThatAreAlwaysConstant() const { return {}; }
/** True if function can be called on default arguments (include Nullable's) and won't throw.
* Counterexample: modulo(0, 0)
*/
virtual bool canBeExecutedOnDefaultArguments() const { return true; }
};
using ExecutableFunctionImplPtr = std::unique_ptr<IExecutableFunctionImpl>;
/// This class generally has the same methods as in IFunctionBase.
/// See comments for IFunctionBase in IFunction.h
/// The main purpose is to implement `prepare` which returns IExecutableFunctionImpl, not IExecutableFunction
/// Inheritance is not used for better readability.
class IFunctionBaseImpl
{
public:
virtual ~IFunctionBaseImpl() = default;
virtual String getName() const = 0;
virtual const DataTypes & getArgumentTypes() const = 0;
virtual const DataTypePtr & getReturnType() const = 0;
virtual ExecutableFunctionImplPtr prepare(const Block & sample_block, const ColumnNumbers & arguments, size_t result) const = 0;
#if USE_EMBEDDED_COMPILER
virtual bool isCompilable() const { return false; }
virtual llvm::Value * compile(llvm::IRBuilderBase & /*builder*/, ValuePlaceholders /*values*/) const
{
throw Exception(getName() + " is not JIT-compilable", ErrorCodes::NOT_IMPLEMENTED);
}
#endif
virtual bool isStateful() const { return false; }
virtual bool isSuitableForConstantFolding() const { return true; }
virtual ColumnPtr getResultIfAlwaysReturnsConstantAndHasArguments(const Block & /*block*/, const ColumnNumbers & /*arguments*/) const { return nullptr; }
virtual bool isInjective(const Block & /*sample_block*/) { return false; }
virtual bool isDeterministic() const { return true; }
virtual bool isDeterministicInScopeOfQuery() const { return true; }
virtual bool hasInformationAboutMonotonicity() const { return false; }
using Monotonicity = IFunctionBase::Monotonicity;
virtual Monotonicity getMonotonicityForRange(const IDataType & /*type*/, const Field & /*left*/, const Field & /*right*/) const
{
throw Exception("Function " + getName() + " has no information about its monotonicity.", ErrorCodes::NOT_IMPLEMENTED);
}
};
using FunctionBaseImplPtr = std::unique_ptr<IFunctionBaseImpl>;
class IFunctionOverloadResolverImpl
{
public:
virtual ~IFunctionOverloadResolverImpl() = default;
virtual String getName() const = 0;
virtual FunctionBaseImplPtr build(const ColumnsWithTypeAndName & arguments, const DataTypePtr & return_type) const = 0;
virtual DataTypePtr getReturnType(const DataTypes & /*arguments*/) const
{
throw Exception("getReturnType is not implemented for " + getName(), ErrorCodes::NOT_IMPLEMENTED);
}
/// This function will be called in default implementation. You can overload it or the previous one.
virtual DataTypePtr getReturnType(const ColumnsWithTypeAndName & arguments) const
{
DataTypes data_types(arguments.size());
for (size_t i = 0; i < arguments.size(); ++i)
data_types[i] = arguments[i].type;
return getReturnType(data_types);
}
/// For non-variadic functions, return number of arguments; otherwise return zero (that should be ignored).
virtual size_t getNumberOfArguments() const = 0;
/// Properties from IFunctionOverloadResolver. See comments in IFunction.h
virtual bool isDeterministic() const { return true; }
virtual bool isDeterministicInScopeOfQuery() const { return true; }
virtual bool isStateful() const { return false; }
virtual bool isVariadic() const { return false; }
/// Will be called if isVariadic returns true. You need to check if function can have specified number of arguments.
virtual void checkNumberOfArgumentsIfVariadic(size_t /*number_of_arguments*/) const
{
throw Exception("checkNumberOfArgumentsIfVariadic is not implemented for " + getName(), ErrorCodes::NOT_IMPLEMENTED);
}
virtual void getLambdaArgumentTypes(DataTypes & /*arguments*/) const
{
throw Exception("Function " + getName() + " can't have lambda-expressions as arguments", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
}
virtual ColumnNumbers getArgumentsThatAreAlwaysConstant() const { return {}; }
virtual ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const { return {}; }
/** If useDefaultImplementationForNulls() is true, than change arguments for getReturnType() and build():
* if some of arguments are Nullable(Nothing) then don't call getReturnType(), call build() with return_type = Nullable(Nothing),
* if some of arguments are Nullable, then:
* - Nullable types are substituted with nested types for getReturnType() function
* - wrap getReturnType() result in Nullable type and pass to build
*
* Otherwise build returns build(arguments, getReturnType(arguments));
*/
virtual bool useDefaultImplementationForNulls() const { return true; }
/** If useDefaultImplementationForNulls() is true, than change arguments for getReturnType() and build().
* If function arguments has low cardinality types, convert them to ordinary types.
* getReturnType returns ColumnLowCardinality if at least one argument type is ColumnLowCardinality.
*/
virtual bool useDefaultImplementationForLowCardinalityColumns() const { return true; }
/// If it isn't, will convert all ColumnLowCardinality arguments to full columns.
virtual bool canBeExecutedOnLowCardinalityDictionary() const { return true; }
};
using FunctionOverloadResolverImplPtr = std::unique_ptr<IFunctionOverloadResolverImpl>;
/// Previous function interface.
class IFunction : public std::enable_shared_from_this<IFunction>
{
public:
virtual ~IFunction() = default;
virtual String getName() const = 0;
virtual void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) = 0;
virtual void executeImplDryRun(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count)
{
executeImpl(block, arguments, result, input_rows_count);
}
/** Default implementation in presence of Nullable arguments or NULL constants as arguments is the following:
* if some of arguments are NULL constants then return NULL constant,
* if some of arguments are Nullable, then execute function as usual for block,
* where Nullable columns are substituted with nested columns (they have arbitrary values in rows corresponding to NULL value)
* and wrap result in Nullable column where NULLs are in all rows where any of arguments are NULL.
*/
virtual bool useDefaultImplementationForNulls() const { return true; }
/** If the function have non-zero number of arguments,
* and if all arguments are constant, that we could automatically provide default implementation:
* arguments are converted to ordinary columns with single value, then function is executed as usual,
* and then the result is converted to constant column.
*/
virtual bool useDefaultImplementationForConstants() const { return false; }
/** If function arguments has single low cardinality column and all other arguments are constants, call function on nested column.
* Otherwise, convert all low cardinality columns to ordinary columns.
* Returns ColumnLowCardinality if at least one argument is ColumnLowCardinality.
*/
virtual bool useDefaultImplementationForLowCardinalityColumns() const { return true; }
/// If it isn't, will convert all ColumnLowCardinality arguments to full columns.
virtual bool canBeExecutedOnLowCardinalityDictionary() const { return true; }
/** Some arguments could remain constant during this implementation.
*/
virtual ColumnNumbers getArgumentsThatAreAlwaysConstant() const { return {}; }
/** True if function can be called on default arguments (include Nullable's) and won't throw.
* Counterexample: modulo(0, 0)
*/
virtual bool canBeExecutedOnDefaultArguments() const { return true; }
#if USE_EMBEDDED_COMPILER
virtual bool isCompilable() const
{
throw Exception("isCompilable without explicit types is not implemented for IFunction", ErrorCodes::NOT_IMPLEMENTED);
}
virtual llvm::Value * compile(llvm::IRBuilderBase & /*builder*/, ValuePlaceholders /*values*/) const
{
throw Exception("compile without explicit types is not implemented for IFunction", ErrorCodes::NOT_IMPLEMENTED);
}
#endif
/// Properties from IFunctionBase (see IFunction.h)
virtual bool isSuitableForConstantFolding() const { return true; }
virtual ColumnPtr getResultIfAlwaysReturnsConstantAndHasArguments(const Block & /*block*/, const ColumnNumbers & /*arguments*/) const { return nullptr; }
virtual bool isInjective(const Block & /*sample_block*/) { return false; }
virtual bool isDeterministic() const { return true; }
virtual bool isDeterministicInScopeOfQuery() const { return true; }
virtual bool isStateful() const { return false; }
virtual bool hasInformationAboutMonotonicity() const { return false; }
using Monotonicity = IFunctionBase::Monotonicity;
virtual Monotonicity getMonotonicityForRange(const IDataType & /*type*/, const Field & /*left*/, const Field & /*right*/) const
{
throw Exception("Function " + getName() + " has no information about its monotonicity.", ErrorCodes::NOT_IMPLEMENTED);
}
/// For non-variadic functions, return number of arguments; otherwise return zero (that should be ignored).
virtual size_t getNumberOfArguments() const = 0;
virtual DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const
{
throw Exception("getReturnType is not implemented for " + getName(), ErrorCodes::NOT_IMPLEMENTED);
}
/// Get the result type by argument type. If the function does not apply to these arguments, throw an exception.
virtual DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const
{
DataTypes data_types(arguments.size());
for (size_t i = 0; i < arguments.size(); ++i)
data_types[i] = arguments[i].type;
return getReturnTypeImpl(data_types);
}
virtual bool isVariadic() const { return false; }
virtual void checkNumberOfArgumentsIfVariadic(size_t /*number_of_arguments*/) const
{
throw Exception("checkNumberOfArgumentsIfVariadic is not implemented for " + getName(), ErrorCodes::NOT_IMPLEMENTED);
}
virtual void getLambdaArgumentTypes(DataTypes & /*arguments*/) const
{
throw Exception("Function " + getName() + " can't have lambda-expressions as arguments", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
}
virtual ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const { return {}; }
#if USE_EMBEDDED_COMPILER
bool isCompilable(const DataTypes & arguments) const;
llvm::Value * compile(llvm::IRBuilderBase &, const DataTypes & arguments, ValuePlaceholders values) const;
#endif
protected:
#if USE_EMBEDDED_COMPILER
virtual bool isCompilableImpl(const DataTypes &) const { return false; }
virtual llvm::Value * compileImpl(llvm::IRBuilderBase &, const DataTypes &, ValuePlaceholders) const
{
throw Exception(getName() + " is not JIT-compilable", ErrorCodes::NOT_IMPLEMENTED);
}
#endif
};
using FunctionPtr = std::shared_ptr<IFunction>;
}