/**
* Copyright 2011 The Apache Software Foundation
*
* 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 java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Random;
import org.apache.hadoop.hbase.KeyValue;
/**
* A filter that includes rows based on a chance.
*
*/
public class RandomRowFilter extends FilterBase {
protected static final Random random = new Random();
protected float chance;
protected boolean filterOutRow;
/**
* Writable constructor, do not use.
*/
public RandomRowFilter() {
}
/**
* Create a new filter with a specified chance for a row to be included.
*
* @param chance
*/
public RandomRowFilter(float chance) {
this.chance = chance;
}
/**
* @return The chance that a row gets included.
*/
public float getChance() {
return chance;
}
/**
* Set the chance that a row is included.
*
* @param chance
*/
public void setChance(float chance) {
this.chance = chance;
}
@Override
public boolean filterAllRemaining() {
return false;
}
@Override
public ReturnCode filterKeyValue(KeyValue v) {
if (filterOutRow) {
return ReturnCode.NEXT_ROW;
}
return ReturnCode.INCLUDE;
}
@Override
public boolean filterRow() {
return filterOutRow;
}
@Override
public boolean filterRowKey(byte[] buffer, int offset, int length) {
if (chance < 0) {
// with a zero chance, the rows is always excluded
filterOutRow = true;
} else if (chance > 1) {
// always included
filterOutRow = false;
} else {
// roll the dice
filterOutRow = !(random.nextFloat() < chance);
}
return filterOutRow;
}
@Override
public void reset() {
filterOutRow = false;
}
@Override
public void readFields(DataInput in) throws IOException {
chance = in.readFloat();
}
@Override
public void write(DataOutput out) throws IOException {
out.writeFloat(chance);
}
}