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added more comments [#CLICKHOUSE-3550]

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This commit is contained in:
Nikolai Kochetov 2018-02-08 19:59:04 +03:00
parent 64b0279af5
commit 733450d1dd
1 changed files with 10 additions and 4 deletions
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14
dbms/src/Functions/IFunction.h
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@ -19,6 +19,10 @@ namespace ErrorCodes
extern const int LOGICAL_ERROR;
}
/// The simplest executable object.
/// Motivation:
/// * Prepare something heavy once before main execution circle instead of doing it for each block.
/// * Provide const interface for IBaseFunction (later).
class IPreparedFunction
{
public:
@ -64,7 +68,7 @@ private:
bool defaultImplementationForConstantArguments(Block & block, const ColumnNumbers & args, size_t result);
};
/// Function with known arguments and return type.
class IFunctionBase
{
public:
@ -153,6 +157,7 @@ public:
using FunctionBasePtr = std::shared_ptr<IFunctionBase>;
/// Creates IBaseFunction from argument types list.
class IFunctionBuilder
{
public:
@ -170,7 +175,7 @@ public:
/// Throw if number of arguments is incorrect. Default implementation will check only in non-variadic case.
virtual void checkNumberOfArguments(size_t number_of_arguments) const = 0;
/// Check arguments and return IFunction.
/// Check arguments and return IBaseFunction.
virtual FunctionBasePtr build(const ColumnsWithTypeAndName & arguments) const = 0;
/// For higher-order functions (functions, that have lambda expression as at least one argument).
@ -234,7 +239,7 @@ protected:
}
};
/// Previous function interface.
class IFunction : public std::enable_shared_from_this<IFunction>,
public FunctionBuilderImpl, public IFunctionBase, public PreparedFunctionImpl
{
@ -276,6 +281,8 @@ protected:
}
};
/// Wrappers over IFunction.
class DefaultExecutable final : public PreparedFunctionImpl
{
public:
@ -342,7 +349,6 @@ public:
size_t getNumberOfArguments() const override { return function->getNumberOfArguments(); }
protected:
/// Get the result type by argument type. If the function does not apply to these arguments, throw an exception.
DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override { return function->getReturnTypeImpl(arguments); }
DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override { return function->getReturnTypeImpl(arguments); }