001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase.filter; 019 020import java.io.IOException; 021import java.util.ArrayList; 022import java.util.Objects; 023import org.apache.hadoop.hbase.Cell; 024import org.apache.hadoop.hbase.exceptions.DeserializationException; 025import org.apache.yetus.audience.InterfaceAudience; 026 027import org.apache.hbase.thirdparty.com.google.common.base.Preconditions; 028import org.apache.hbase.thirdparty.com.google.protobuf.InvalidProtocolBufferException; 029 030import org.apache.hadoop.hbase.shaded.protobuf.generated.FilterProtos; 031 032/** 033 * A filter that will only return the first KV from each row. 034 * <p> 035 * This filter can be used to more efficiently perform row count operations. 036 */ 037@InterfaceAudience.Public 038public class FirstKeyOnlyFilter extends FilterBase { 039 private boolean foundKV = false; 040 041 public FirstKeyOnlyFilter() { 042 } 043 044 @Override 045 public void reset() { 046 foundKV = false; 047 } 048 049 @Override 050 public boolean filterRowKey(Cell cell) throws IOException { 051 // Impl in FilterBase might do unnecessary copy for Off heap backed Cells. 052 return false; 053 } 054 055 @Override 056 public ReturnCode filterCell(final Cell c) { 057 if (foundKV) return ReturnCode.NEXT_ROW; 058 foundKV = true; 059 return ReturnCode.INCLUDE; 060 } 061 062 public static Filter createFilterFromArguments(ArrayList<byte[]> filterArguments) { 063 Preconditions.checkArgument(filterArguments.isEmpty(), "Expected 0 but got: %s", 064 filterArguments.size()); 065 return new FirstKeyOnlyFilter(); 066 } 067 068 /** 069 * @return true if first KV has been found. 070 */ 071 protected boolean hasFoundKV() { 072 return this.foundKV; 073 } 074 075 /** 076 * @param value update {@link #foundKV} flag with value. 077 */ 078 protected void setFoundKV(boolean value) { 079 this.foundKV = value; 080 } 081 082 /** 083 * @return The filter serialized using pb 084 */ 085 @Override 086 public byte[] toByteArray() { 087 FilterProtos.FirstKeyOnlyFilter.Builder builder = FilterProtos.FirstKeyOnlyFilter.newBuilder(); 088 return builder.build().toByteArray(); 089 } 090 091 /** 092 * @param pbBytes A pb serialized {@link FirstKeyOnlyFilter} instance 093 * @return An instance of {@link FirstKeyOnlyFilter} made from <code>bytes</code> 094 * @throws org.apache.hadoop.hbase.exceptions.DeserializationException 095 * @see #toByteArray 096 */ 097 public static FirstKeyOnlyFilter parseFrom(final byte[] pbBytes) throws DeserializationException { 098 // There is nothing to deserialize. Why do this at all? 099 try { 100 FilterProtos.FirstKeyOnlyFilter.parseFrom(pbBytes); 101 } catch (InvalidProtocolBufferException e) { 102 throw new DeserializationException(e); 103 } 104 // Just return a new instance. 105 return new FirstKeyOnlyFilter(); 106 } 107 108 /** 109 * @param o the other filter to compare with 110 * @return true if and only if the fields of the filter that are serialized are equal to the 111 * corresponding fields in other. Used for testing. 112 */ 113 @Override 114 boolean areSerializedFieldsEqual(Filter o) { 115 if (o == this) return true; 116 if (!(o instanceof FirstKeyOnlyFilter)) return false; 117 118 return true; 119 } 120 121 @Override 122 public boolean equals(Object obj) { 123 return obj instanceof Filter && areSerializedFieldsEqual((Filter) obj); 124 } 125 126 @Override 127 public int hashCode() { 128 return Objects.hashCode(foundKV); 129 } 130}