/*
* Copyright (C) 2014 The Async HBase Authors. All rights reserved.
* This file is part of Async HBase.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - Neither the name of the StumbleUpon nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package org.hbase.async;
import org.jboss.netty.buffer.ChannelBuffer;
import org.hbase.async.generated.FilterPB;
import org.hbase.async.generated.HBasePB;
/**
* A filter that will only return the first KV from each row.
* This filter can be used to more efficiently perform row count operations.
*/
public class FirstKeyOnlyFilter extends ScanFilter {
private static final byte[] NAME =
Bytes.UTF8("org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter");
public FirstKeyOnlyFilter() { }
@Override
byte[] name() {
return NAME;
}
@Override
byte[] serialize() {
return FilterPB
.FirstKeyOnlyFilter
.newBuilder()
.build()
.toByteArray();
}
@Override
void serializeOld(ChannelBuffer buf) {
// Write the filter name
buf.writeByte((byte) name().length); // 1
buf.writeBytes(name()); // name().length
}
@Override
int predictSerializedSize() {
return 1 + name().length;
}
@Override
public String toString() {
return getClass().getSimpleName();
}
}