/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.filter;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.hbase.DeserializationException;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.protobuf.generated.FilterProtos;
import java.util.ArrayList;
import com.google.common.base.Preconditions;
import com.google.protobuf.InvalidProtocolBufferException;
/**
* A filter that will only return the first KV from each row.
* <p>
* This filter can be used to more efficiently perform row count operations.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class FirstKeyOnlyFilter extends FilterBase {
private boolean foundKV = false;
public FirstKeyOnlyFilter() {
}
public void reset() {
foundKV = false;
}
public ReturnCode filterKeyValue(KeyValue v) {
if(foundKV) return ReturnCode.NEXT_ROW;
foundKV = true;
return ReturnCode.INCLUDE;
}
public static Filter createFilterFromArguments(ArrayList<byte []> filterArguments) {
Preconditions.checkArgument(filterArguments.size() == 0,
"Expected 0 but got: %s", filterArguments.size());
return new FirstKeyOnlyFilter();
}
/**
* @return true if first KV has been found.
*/
protected boolean hasFoundKV() {
return this.foundKV;
}
/**
*
* @param value update {@link #foundKV} flag with value.
*/
protected void setFoundKV(boolean value) {
this.foundKV = value;
}
/**
* @return The filter serialized using pb
*/
public byte [] toByteArray() {
FilterProtos.FirstKeyOnlyFilter.Builder builder =
FilterProtos.FirstKeyOnlyFilter.newBuilder();
return builder.build().toByteArray();
}
/**
* @param pbBytes A pb serialized {@link FirstKeyOnlyFilter} instance
* @return An instance of {@link FirstKeyOnlyFilter} made from <code>bytes</code>
* @throws DeserializationException
* @see #toByteArray
*/
public static FirstKeyOnlyFilter parseFrom(final byte [] pbBytes)
throws DeserializationException {
// There is nothing to deserialize. Why do this at all?
try {
FilterProtos.FirstKeyOnlyFilter.parseFrom(pbBytes);
} catch (InvalidProtocolBufferException e) {
throw new DeserializationException(e);
}
// Just return a new instance.
return new FirstKeyOnlyFilter();
}
/**
* @param other
* @return true if and only if the fields of the filter that are serialized
* are equal to the corresponding fields in other. Used for testing.
*/
boolean areSerializedFieldsEqual(Filter o) {
if (o == this) return true;
if (!(o instanceof FirstKeyOnlyFilter)) return false;
return true;
}
}