functionisvalid.java

来自「High performance DB query」· Java 代码 · 共 84 行

/*
 * @(#)$Id: FunctionIsvalid.java,v 1.3 2005/03/07 17:27:33 huebsch Exp $
 *
 * Copyright (c) 2001-2004 Regents of the University of California.
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached BERKELEY-LICENSE
 * file. If you do not find these files, copies can be found by writing to:
 * Computer Science Division, Database Group, Universite of California,
 * 617 Soda Hall #1776, Berkeley, CA 94720-1776. Attention: Berkeley License
 *
 * Copyright (c) 2003-2004 Intel Corporation. All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE file.
 * If you do not find these files, copies can be found by writing to:
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300,
 * Berkeley, CA, 94704.  Attention:  Intel License Inquiry.
 */


package pier.helpers.functions;

import pier.data.Tuple;
import pier.expressions.Expression;

/**
 * Class FunctionConcat
 *
 */
public class FunctionIsvalid implements FunctionSelfEvalExp {

    /**
     * Method evaluate
     *
     * @param parameters
     * @return
     */
    public Object evaluate(Object[] parameters) {
        throw new RuntimeException(
            "Illegal call, function requires expressions");
    }

    /**
     * Method evaluate
     *
     * @param parameters
     * @param theTuple
     * @return
     */
    public Object evaluate(Expression[] parameters, Tuple theTuple) {
        int params = parameters.length;

        if ((params == 2) || (params == 3)) {
            boolean valid = true;

            try {
                parameters[0].evaluate(theTuple);
            } catch (Exception exception) {
                valid = false;
            }

            if (valid) {
                return parameters[1].evaluate(theTuple);
            } else {
                if (params == 3) {
                    return parameters[2].evaluate(theTuple);
                } else {
                    return null;
                }
            }
        } else {
            return null;
        }
    }

    /**
     * Method cacheable
     * @return
     */
    public boolean cacheable() {
        return true;
    }
}