| /* |
| * 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.cassandra.fqltool; |
| |
| import java.util.PriorityQueue; |
| |
| import net.openhft.chronicle.queue.ExcerptTailer; |
| import org.apache.cassandra.utils.AbstractIterator; |
| |
| public class FQLQueryIterator extends AbstractIterator<FQLQuery> |
| { |
| // use a priority queue to be able to sort the head of the query logs in memory |
| private final PriorityQueue<FQLQuery> pq; |
| private final ExcerptTailer tailer; |
| private final FQLQueryReader reader; |
| |
| /** |
| * Create an iterator over the FQLQueries in tailer |
| * |
| * Reads up to readAhead queries in to memory to be able to sort them (the files are mostly sorted already) |
| */ |
| public FQLQueryIterator(ExcerptTailer tailer, int readAhead) |
| { |
| assert readAhead > 0 : "readAhead needs to be > 0"; |
| reader = new FQLQueryReader(); |
| this.tailer = tailer; |
| pq = new PriorityQueue<>(readAhead); |
| for (int i = 0; i < readAhead; i++) |
| { |
| FQLQuery next = readNext(); |
| if (next != null) |
| pq.add(next); |
| else |
| break; |
| } |
| } |
| |
| protected FQLQuery computeNext() |
| { |
| FQLQuery q = pq.poll(); |
| if (q == null) |
| return endOfData(); |
| FQLQuery next = readNext(); |
| if (next != null) |
| pq.add(next); |
| return q; |
| } |
| |
| private FQLQuery readNext() |
| { |
| if (tailer.readDocument(reader)) |
| return reader.getQuery(); |
| return null; |
| } |
| } |
| |