phoenix-core/src/main/java/org/apache/phoenix/iterate/ResultIterator.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.phoenix.iterate;

import java.sql.SQLException;
import java.util.List;

import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.util.SQLCloseable;


public interface ResultIterator extends SQLCloseable {
    public static final ResultIterator EMPTY_ITERATOR = new ResultIterator() {
        @Override
        public void close() throws SQLException {
        }

        @Override
        public Tuple next() throws SQLException {
            return null;
        }

        @Override
        public void explain(List<String> planSteps) {
        }
    };

    /**
     * Grab the next row's worth of values. The iterator will return a Tuple.
     * @return Tuple object if there is another row, null if the scanner is
     * exhausted.
     * @throws SQLException e
     */
    public Tuple next() throws SQLException;
    
    public void explain(List<String> planSteps);
}