CollapseFilters.h

Go to the documentation of this file.

/*
 * Souffle - A Datalog Compiler
 * Copyright (c) 2018, The Souffle Developers. All rights reserved
 * Licensed under the Universal Permissive License v 1.0 as shown at:
 * - https://opensource.org/licenses/UPL
 * - <souffle root>/licenses/SOUFFLE-UPL.txt
 */
 
/************************************************************************
 *
 * @file CollapseFilters.h
 *
 ***********************************************************************/
 
#pragma once
 
#include "ram/Program.h"
#include "ram/TranslationUnit.h"
#include "ram/transform/Transformer.h"
#include <string>
 
namespace souffle::ram::transform {
 
/**
 * @class CollapseFiltersTransformer
 * @brief Transforms consecutive filters into a single filter containing a conjunction
 *
 * For example ..
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *  QUERY
 *   ...
 *    IF C1
 *     IF C2
 *      ...
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 * will be rewritten to
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *  QUERY
 *   ...
 *    IF C1 /\ C2 then
 *     ...
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 */
class CollapseFiltersTransformer : public Transformer {
public:
    std::string getName() const override {
        return "CollapseFiltersTransformer";
    }
 
    /**
     * @brief Collapse consecutive filter operations
     * @param program Program that is transformed
     * @return Flag showing whether the program has been changed by the transformation
     */
    bool collapseFilters(Program& program);
 
protected:
    bool transform(TranslationUnit& translationUnit) override {
        return collapseFilters(translationUnit.getProgram());
    }
};
 
}  // namespace souffle::ram::transform