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 * Simple filter that returns first N columns on row only. This filter was written to test filters
034 * in Get and as soon as it gets its quota of columns, {@link #filterAllRemaining()} returns true.
035 * This makes this filter unsuitable as a Scan filter.
036 */
037@InterfaceAudience.Public
038public class ColumnCountGetFilter extends FilterBase {
039  private int limit = 0;
040  private int count = 0;
041
042  public ColumnCountGetFilter(final int n) {
043    Preconditions.checkArgument(n >= 0, "limit be positive %s", n);
044    this.limit = n;
045  }
046
047  public int getLimit() {
048    return limit;
049  }
050
051  @Override
052  public boolean filterRowKey(Cell cell) throws IOException {
053    // Impl in FilterBase might do unnecessary copy for Off heap backed Cells.
054    if (filterAllRemaining()) return true;
055    return false;
056  }
057
058  @Override
059  public boolean filterAllRemaining() {
060    return this.count > this.limit;
061  }
062
063  @Override
064  public ReturnCode filterCell(final Cell c) {
065    this.count++;
066    return filterAllRemaining() ? ReturnCode.NEXT_COL : ReturnCode.INCLUDE_AND_NEXT_COL;
067  }
068
069  @Override
070  public void reset() {
071    this.count = 0;
072  }
073
074  public static Filter createFilterFromArguments(ArrayList<byte[]> filterArguments) {
075    Preconditions.checkArgument(filterArguments.size() == 1, "Expected 1 but got: %s",
076      filterArguments.size());
077    int limit = ParseFilter.convertByteArrayToInt(filterArguments.get(0));
078    return new ColumnCountGetFilter(limit);
079  }
080
081  /** Returns The filter serialized using pb */
082  @Override
083  public byte[] toByteArray() {
084    FilterProtos.ColumnCountGetFilter.Builder builder =
085      FilterProtos.ColumnCountGetFilter.newBuilder();
086    builder.setLimit(this.limit);
087    return builder.build().toByteArray();
088  }
089
090  /**
091   * Parse a serialized representation of {@link ColumnCountGetFilter}
092   * @param pbBytes A pb serialized {@link ColumnCountGetFilter} instance
093   * @return An instance of {@link ColumnCountGetFilter} made from <code>bytes</code>
094   * @throws DeserializationException if an error occurred
095   * @see #toByteArray
096   */
097  public static ColumnCountGetFilter parseFrom(final byte[] pbBytes)
098    throws DeserializationException {
099    FilterProtos.ColumnCountGetFilter proto;
100    try {
101      proto = FilterProtos.ColumnCountGetFilter.parseFrom(pbBytes);
102    } catch (InvalidProtocolBufferException e) {
103      throw new DeserializationException(e);
104    }
105    return new ColumnCountGetFilter(proto.getLimit());
106  }
107
108  /**
109   * Returns true if and only if the fields of the filter that are serialized are equal to the
110   * corresponding fields in other. Used for testing.
111   */
112  @Override
113  boolean areSerializedFieldsEqual(Filter o) {
114    if (o == this) {
115      return true;
116    }
117    if (!(o instanceof ColumnCountGetFilter)) {
118      return false;
119    }
120    ColumnCountGetFilter other = (ColumnCountGetFilter) o;
121    return this.getLimit() == other.getLimit();
122  }
123
124  @Override
125  public String toString() {
126    return this.getClass().getSimpleName() + " " + this.limit;
127  }
128
129  @Override
130  public boolean equals(Object obj) {
131    return obj instanceof Filter && areSerializedFieldsEqual((Filter) obj);
132  }
133
134  @Override
135  public int hashCode() {
136    return Objects.hash(this.limit);
137  }
138}