/*
* Copyright 2010 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.ArrayList;
import org.apache.hadoop.hbase.KeyValue;
import com.google.common.base.Preconditions;
/**
* A filter, based on the ColumnCountGetFilter, takes two arguments: limit and offset.
* This filter can be used for row-based indexing, where references to other tables are stored across many columns,
* in order to efficient lookups and paginated results for end users.
*/
public class ColumnPaginationFilter extends FilterBase
{
private int limit = 0;
private int offset = 0;
private int count = 0;
/**
* Used during serialization. Do not use.
*/
public ColumnPaginationFilter()
{
super();
}
public ColumnPaginationFilter(final int limit, final int offset)
{
Preconditions.checkArgument(limit >= 0, "limit must be positive %s", limit);
Preconditions.checkArgument(offset >= 0, "offset must be positive %s", offset);
this.limit = limit;
this.offset = offset;
}
/**
* @return limit
*/
public int getLimit() {
return limit;
}
/**
* @return offset
*/
public int getOffset() {
return offset;
}
@Override
public ReturnCode filterKeyValue(KeyValue v)
{
if(count >= offset + limit)
{
return ReturnCode.NEXT_ROW;
}
ReturnCode code = count < offset ? ReturnCode.SKIP : ReturnCode.INCLUDE;
count++;
return code;
}
@Override
public void reset()
{
this.count = 0;
}
public static Filter createFilterFromArguments(ArrayList<byte []> filterArguments) {
Preconditions.checkArgument(filterArguments.size() == 2,
"Expected 2 but got: %s", filterArguments.size());
int limit = ParseFilter.convertByteArrayToInt(filterArguments.get(0));
int offset = ParseFilter.convertByteArrayToInt(filterArguments.get(1));
return new ColumnPaginationFilter(limit, offset);
}
public void readFields(DataInput in) throws IOException
{
this.limit = in.readInt();
this.offset = in.readInt();
}
public void write(DataOutput out) throws IOException
{
out.writeInt(this.limit);
out.writeInt(this.offset);
}
}