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 org.apache.hadoop.hbase.Cell;
023import org.apache.hadoop.hbase.exceptions.DeserializationException;
024import org.apache.yetus.audience.InterfaceAudience;
025
026import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;
027import org.apache.hbase.thirdparty.com.google.protobuf.InvalidProtocolBufferException;
028
029import org.apache.hadoop.hbase.shaded.protobuf.generated.FilterProtos;
030
031/**
032 * A filter that will only return the first KV from each row.
033 * <p>
034 * This filter can be used to more efficiently perform row count operations.
035 */
036@InterfaceAudience.Public
037public class FirstKeyOnlyFilter extends FilterBase {
038  private boolean foundKV = false;
039
040  public FirstKeyOnlyFilter() {
041  }
042
043  @Override
044  public void reset() {
045    foundKV = false;
046  }
047
048  @Override
049  public boolean filterRowKey(Cell cell) throws IOException {
050    // Impl in FilterBase might do unnecessary copy for Off heap backed Cells.
051    return false;
052  }
053
054  @Deprecated
055  @Override
056  public ReturnCode filterKeyValue(final Cell c) {
057    return filterCell(c);
058  }
059
060  @Override
061  public ReturnCode filterCell(final Cell c) {
062    if (foundKV) return ReturnCode.NEXT_ROW;
063    foundKV = true;
064    return ReturnCode.INCLUDE;
065  }
066
067  public static Filter createFilterFromArguments(ArrayList<byte[]> filterArguments) {
068    Preconditions.checkArgument(filterArguments.isEmpty(), "Expected 0 but got: %s",
069      filterArguments.size());
070    return new FirstKeyOnlyFilter();
071  }
072
073  /** Returns true if first KV has been found. */
074  protected boolean hasFoundKV() {
075    return this.foundKV;
076  }
077
078  /**
079   * Set or clear the indication if the first KV has been found.
080   * @param value update {@link #foundKV} flag with value.
081   */
082  protected void setFoundKV(boolean value) {
083    this.foundKV = value;
084  }
085
086  /** Returns The filter serialized using pb */
087  @Override
088  public byte[] toByteArray() {
089    FilterProtos.FirstKeyOnlyFilter.Builder builder = FilterProtos.FirstKeyOnlyFilter.newBuilder();
090    return builder.build().toByteArray();
091  }
092
093  /**
094   * Parse a serialized representation of {@link FirstKeyOnlyFilter}
095   * @param pbBytes A pb serialized {@link FirstKeyOnlyFilter} instance
096   * @return An instance of {@link FirstKeyOnlyFilter} made from <code>bytes</code>
097   * @throws DeserializationException if an error occurred
098   * @see #toByteArray
099   */
100  public static FirstKeyOnlyFilter parseFrom(final byte[] pbBytes) throws DeserializationException {
101    // There is nothing to deserialize. Why do this at all?
102    try {
103      FilterProtos.FirstKeyOnlyFilter.parseFrom(pbBytes);
104    } catch (InvalidProtocolBufferException e) {
105      throw new DeserializationException(e);
106    }
107    // Just return a new instance.
108    return new FirstKeyOnlyFilter();
109  }
110
111  /**
112   * Returns true if and only if the fields of the filter that are serialized are equal to the
113   * corresponding fields in other. Used for testing.
114   */
115  @Override
116  boolean areSerializedFieldsEqual(Filter o) {
117    if (o == this) {
118      return true;
119    }
120    if (!(o instanceof FirstKeyOnlyFilter)) {
121      return false;
122    }
123    return true;
124  }
125
126  @Override
127  public boolean equals(Object obj) {
128    return obj instanceof Filter && areSerializedFieldsEqual((Filter) obj);
129  }
130
131  @Override
132  public int hashCode() {
133    return Boolean.hashCode(foundKV);
134  }
135}