RemoveEmptyRelations.h

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/*
 * Souffle - A Datalog Compiler
 * Copyright (c) 2015, Oracle and/or its affiliates. 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 RemoveEmptyRelations.h
 *
 ***********************************************************************/
 
#pragma once
 
#include "ast/QualifiedName.h"
#include "ast/TranslationUnit.h"
#include "ast/transform/Transformer.h"
#include <string>
 
namespace souffle::ast::transform {
 
/**
 * Transformation pass to remove all empty relations and rules that use empty relations.
 */
class RemoveEmptyRelationsTransformer : public Transformer {
public:
    std::string getName() const override {
        return "RemoveEmptyRelationsTransformer";
    }
 
    /**
     * Eliminate all empty relations (and their uses) in the given program.
     *
     * @param translationUnit the program to be processed
     * @return whether the program was modified
     */
    static bool removeEmptyRelations(TranslationUnit& translationUnit);
 
    RemoveEmptyRelationsTransformer* clone() const override {
        return new RemoveEmptyRelationsTransformer();
    }
 
private:
    bool transform(TranslationUnit& translationUnit) override {
        return removeEmptyRelations(translationUnit);
    }
 
    /**
     * Eliminate rules that contain empty relations and/or rewrite them.
     *
     * @param translationUnit the program to be processed
     * @param emptyRelation relation that is empty
     * @return whether the program was modified
     */
    static bool removeEmptyRelationUses(TranslationUnit& translationUnit, const QualifiedName& emptyRelation);
};
 
}  // namespace souffle::ast::transform