1 /** 2 * Copyright 2010 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.filter; 21 22 import org.apache.hadoop.hbase.KeyValue; 23 24 import java.io.DataInput; 25 import java.io.DataOutput; 26 import java.io.IOException; 27 import java.util.List; 28 29 /** 30 * Implementation of Filter interface that limits results to a specific page 31 * size. It terminates scanning once the number of filter-passed rows is > 32 * the given page size. 33 * <p> 34 * Note that this filter cannot guarantee that the number of results returned 35 * to a client are <= page size. This is because the filter is applied 36 * separately on different region servers. It does however optimize the scan of 37 * individual HRegions by making sure that the page size is never exceeded 38 * locally. 39 */ 40 public class PageFilter extends FilterBase { 41 private long pageSize = Long.MAX_VALUE; 42 private int rowsAccepted = 0; 43 44 /** 45 * Default constructor, filters nothing. Required though for RPC 46 * deserialization. 47 */ 48 public PageFilter() { 49 super(); 50 } 51 52 /** 53 * Constructor that takes a maximum page size. 54 * 55 * @param pageSize Maximum result size. 56 */ 57 public PageFilter(final long pageSize) { 58 this.pageSize = pageSize; 59 } 60 61 public long getPageSize() { 62 return pageSize; 63 } 64 65 public boolean filterAllRemaining() { 66 return this.rowsAccepted >= this.pageSize; 67 } 68 69 public boolean filterRow() { 70 this.rowsAccepted++; 71 return this.rowsAccepted > this.pageSize; 72 } 73 74 public void readFields(final DataInput in) throws IOException { 75 this.pageSize = in.readLong(); 76 } 77 78 public void write(final DataOutput out) throws IOException { 79 out.writeLong(pageSize); 80 } 81 }