| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| **/ |
| |
| #ifndef QUICKSTEP_EXPRESSIONS_TABLE_GENERATOR_GENERATOR_FUNCTION_HPP_ |
| #define QUICKSTEP_EXPRESSIONS_TABLE_GENERATOR_GENERATOR_FUNCTION_HPP_ |
| |
| #include <exception> |
| #include <string> |
| #include <vector> |
| |
| #include "utility/Macros.hpp" |
| |
| namespace quickstep { |
| |
| class GeneratorFunctionHandle; |
| class TypedValue; |
| |
| /** \addtogroup Expressions |
| * @{ |
| */ |
| |
| /** |
| * @brief A class representing a particular generator function in the abstract |
| * sense. |
| * |
| * Generator functions are used for generating tables. A generator function |
| * takes a list of constant arguments at query compile time, and populates the |
| * given ColumnVectorValueAccesor at query run time. |
| * |
| * The GeneratorFunction class provides informational methods about the |
| * applicability of a particular generator function to particular constant |
| * arguments. The actual implementation of the generator functions' logic is in |
| * the GeneratorFunctionHandle class hierarchy, and can be different depending |
| * on the particular arguments given to the function. At query compile time, |
| * a caller should first call GeneratorFunction::generateHandle() to instantiate |
| * an GeneratorFunctionHandle object. The handle object provides information |
| * about the concrete function, e.g. the number and types of the output columns |
| * Then, at query run time, the backend also uses the handle object's methods |
| * to actually generate a table. |
| * |
| * To add a new generator function, subclass both GeneratorFunction and |
| * GeneratorFunctionHandle to implement the logics. Also add a line in |
| * GeneratorFunctionFactory's constructor to make the new function registered. |
| * |
| * See GenerateSeries and GenerateSeriesHandle as an example of how to implement |
| * new generator funcitons. |
| **/ |
| class GeneratorFunction { |
| public: |
| /** |
| * @brief Get the name of this generator function. The name should be unique |
| * as it is used to register this function into the generator function pool. |
| * |
| * @return The name of this generator function. |
| **/ |
| virtual const std::string getName() const = 0; |
| |
| /** |
| * @brief Get the usage syntax of this generator function in text form. The |
| * syntax information will be displayed when the end users ask for help |
| * on the usage of this function. |
| * |
| * @return The usage syntax of this generator function in text form. |
| **/ |
| virtual const std::string getSyntax() const = 0; |
| |
| /** |
| * @brief Create an GeneratorFunctionHandle. |
| * |
| * @param arguments A list of zero or more constant arguments to this |
| * generator funciton. |
| * @exception GeneratorFunctionInvalidArguments The arguments to this |
| * generator function are invalid. |
| * @return A new GeneratorFunctionHandle object that is used to do the actual |
| * table generation. Caller is responsible for deleting the returned |
| * object. |
| **/ |
| virtual GeneratorFunctionHandle* createHandle( |
| const std::vector<TypedValue> &arguments) const = 0; |
| |
| protected: |
| GeneratorFunction() { |
| } |
| |
| private: |
| DISALLOW_COPY_AND_ASSIGN(GeneratorFunction); |
| }; |
| |
| |
| /** |
| * @brief Exception thrown for invalid arguments to a generator function. |
| **/ |
| class GeneratorFunctionInvalidArguments : public std::exception { |
| public: |
| /** |
| * @brief Constructor. |
| * |
| * @param message The error message. |
| **/ |
| explicit GeneratorFunctionInvalidArguments(const std::string &message) |
| : message_(message) { |
| } |
| |
| ~GeneratorFunctionInvalidArguments() throw() { |
| } |
| |
| virtual const char* what() const throw() { |
| return message_.c_str(); |
| } |
| |
| private: |
| std::string message_; |
| }; |
| |
| /** @} */ |
| |
| } // namespace quickstep |
| |
| #endif /* QUICKSTEP_EXPRESSIONS_TABLE_GENERATOR_GENERATOR_FUNCTION_HPP_ */ |