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