QueryEnvironment.java #3

/*
// $Id: //guest/julian_hyde/saffron/src/main/openjava/mop/QueryEnvironment.java#3 $
// Saffron preprocessor and data engine
// Copyright (C) 2002 Julian Hyde <julian.hyde@mail.com>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 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
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the
// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA  02111-1307, USA.
//
// See the COPYING file located in the top-level-directory of
// the archive of this library for complete text of license.
*/

package openjava.mop;
import openjava.ptree.Expression;
import openjava.ptree.QueryExpression;
import openjava.ptree.SetExpression;

/**
 * <code>QueryEnvironment</code> is the environment seen inside a {@link
 * QueryExpression}.  The 'variables' are the tables in the from list; it
 * inherits stuff from the enclosing java environment, plus from enclosing
 * queries.  TBD: can queries in a from list inherit?
 */
public class QueryEnvironment extends ClosedEnvironment {
    private QueryExpression query;

    public QueryEnvironment(Environment e, QueryExpression query)
    {
	super(e);
	this.query = query;
    }

    // implement Environment
    public OJClass lookupBind(String name) {
	Expression[] expressions = SetExpression.flatten(query.getFrom());
	for (int i = 0; i < expressions.length; i++) {
	    String alias = Toolbox.getAlias(expressions[i]);
	    if (alias != null && alias.equals(name)) {
		try {
		    return expressions[i].getRowType(parent);
		} catch (Exception e) {
		    System.err.println(
			"unexpected exception : " + e.toString() );
		    break;
		}
	    }
	}
	return parent.lookupBind(name);
    }

    // implement Environment
    public boolean isBind(String name)
    {
	Expression expression = lookupFrom(name);
	if (expression != null) {
	    return true;
	}
	if (parent != null) {
	    return parent.isBind(name);
	}
	return false;
    }

    /**
     * Looks for a from-list item called <code>name</code>.
     *
     * @param name name of from-list item
     * @param offset writes the zero-based offset to <code>offset[0]</code> if
     *     the item is found
     * @return the expression if found, null if not
     */
    public Expression lookupFrom(String name, int[] offset) {
	Expression[] expressions = SetExpression.flatten(query.getFrom());
	for (int i = 0; i < expressions.length; i++) {
	    Expression expression = expressions[i];
	    String alias = Toolbox.getAlias(expression);
	    if (alias != null && alias.equals(name)) {
		if (offset != null) {
		    offset[0] = i;
		}
		return expression;
	    }
	}
	return null; // not found
    }

    public Expression lookupFrom(String name) {
	return lookupFrom(name, null);
    }

    public boolean isAggregating()
    {
	return query.getGroupList() != null;
    }
}


// End QueryEnvironment.java