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* Copyright 2009 The Apache Software Foundation
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.hadoop.hbase.filter;
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import java.io.DataInput;
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import java.io.DataOutput;
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import java.io.IOException;
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import org.apache.hadoop.hbase.KeyValue;
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* Implementation of Filter interface that limits results to a specific page
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* size. It terminates scanning once the number of filter-passed rows is >
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* the given page size.
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* Note that this filter cannot guarantee that the number of results returned
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* to a client are <= page size. This is because the filter is applied
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* separately on different region servers. It does however optimize the scan of
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* individual HRegions by making sure that the page size is never exceeded
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public class PageFilter implements Filter {
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private long pageSize = Long.MAX_VALUE;
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private int rowsAccepted = 0;
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* Default constructor, filters nothing. Required though for RPC
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* Constructor that takes a maximum page size.
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* @param pageSize Maximum result size.
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public PageFilter(final long pageSize) {
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this.pageSize = pageSize;
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public long getPageSize() {
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public boolean filterAllRemaining() {
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return this.rowsAccepted >= this.pageSize;
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public boolean filterRowKey(byte[] rowKey, int offset, int length) {
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public void readFields(final DataInput in) throws IOException {
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this.pageSize = in.readLong();
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public void write(final DataOutput out) throws IOException {
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out.writeLong(pageSize);
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public ReturnCode filterKeyValue(KeyValue v) {
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return ReturnCode.INCLUDE;
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public boolean filterRow() {
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return this.rowsAccepted > this.pageSize;
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