core/src/main/java/org/apache/mrql/MRQL.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.mrql;

import java.io.*;


/** API for dynamic MRQL queries */
final public class MRQL extends Interpreter {

    /** evaluate an MRQL query in a string
     * @param query a string that contains an MRQL query
     * @return the evaluation result
     */
    public static MRData query ( String query ) {
        evaluate("store tt := "+query+";");
        return variable_lookup("tt",global_env);
    }

    /** evaluate MRQL statments in a string
     * @param command a string that contains MRQL commands separated by ;
     */
    public static void evaluate ( String command ) {
        try {
            MRQLLex scanner = new MRQLLex(new StringReader(command));
            MRQLParser parser = new MRQLParser(scanner);
            parser.setScanner(scanner);
            MRQLLex.reset();
            parser.parse();
        } catch (Exception x) {
            x.printStackTrace();
            throw new Error(x);
        }
    }

    /** clean up the MRQL workspace */
    public static void clean () {
        try {
            Plan.clean();
        } catch (IOException ex) {
            throw new Error("Failed to clean-up temporary files");
        }
    }
}