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

/**
 * Iterates through tuples up to a limit
 *
 * @since 1.2
 */
public class OffsetResultIterator extends DelegateResultIterator {
    private int rowCount;
    private int offset;

    public OffsetResultIterator(ResultIterator delegate, Integer offset) {
        super(delegate);
        this.offset = offset == null ? -1 : offset;
    }

    @Override
    public Tuple next() throws SQLException {
        while (rowCount < offset) {
            if (super.next() == null) { return null; }
            rowCount++;
        }
        return super.next();
    }

    @Override
    public void explain(List<String> planSteps) {
        super.explain(planSteps);
        planSteps.add("CLIENT OFFSET " + offset);
    }

    @Override
    public String toString() {
        return "OffsetResultIterator [rowCount=" + rowCount + ", offset=" + offset + "]";
    }

    public Integer getRemainingOffset() {
        return (offset - rowCount) > 0 ? (offset - rowCount) : 0;
    }
}