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/*
 * eXist-db Open Source Native XML Database
 * Copyright (C) 2001 The eXist-db Authors
 *
 * [email protected]
 * http://www.exist-db.org
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.xquery;

/**
 * Base class to be implemented by an index module if it wants to rewrite
 * certain query expressions. Subclasses should overwrite the rewriteXXX methods
 * they are interested in.
 *
 * @author Wolfgang Meier
 */
public class QueryRewriter {

    private final XQueryContext context;

    public QueryRewriter(XQueryContext context) {
        this.context = context;
    }

    /**
     * Rewrite the expression to make use of indexes. The method may also return an additional
     * pragma to be added to the extension expression which is inserted by the optimizer.
     *
     * @param locationStep the location step to rewrite
     * @return a pragma expression to replace the step or null if not applicable
     * @throws XPathException in case of a static error
     */
    public Pragma rewriteLocationStep(LocationStep locationStep) throws XPathException {
        return null;
    }

    protected XQueryContext getContext() {
        return context;
    }
}