Clear.h

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/*
 * Souffle - A Datalog Compiler
 * Copyright (c) 2013, 2014, 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 Clear.h
 *
 * Defines abstract class Statement and sub-classes for implementing the
 * Relational Algebra Machine (RAM), which is an abstract machine.
 *
 ***********************************************************************/
 
#pragma once
 
#include "ram/Relation.h"
#include "ram/RelationStatement.h"
#include "souffle/utility/MiscUtil.h"
#include "souffle/utility/StreamUtil.h"
#include <memory>
#include <ostream>
#include <string>
#include <utility>
 
namespace souffle::ram {
 
/**
 * @class Clear
 * @brief Delete tuples of a relation
 *
 * This retains the target relation, but cleans its content
 *
 * For example:
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * CLEAR A
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
 
class Clear : public RelationStatement {
public:
    Clear(std::string rel) : RelationStatement(rel) {}
 
    Clear* clone() const override {
        return new Clear(relation);
    }
 
protected:
    void print(std::ostream& os, int tabpos) const override {
        os << times(" ", tabpos);
        os << "CLEAR " << relation << std::endl;
    }
};
 
}  // namespace souffle::ram