/**
*
* 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;
/**
* Implementation of Filter interface that limits results to a specific page
* size. It terminates scanning once the number of filter-passed rows is >
* the given page size.
* <p>
* Note that this filter cannot guarantee that the number of results returned
* to a client are <= page size. This is because the filter is applied
* separately on different region servers. It does however optimize the scan of
* individual HRegions by making sure that the page size is never exceeded
* locally.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class PageFilter extends FilterBase {
private long pageSize = Long.MAX_VALUE;
private int rowsAccepted = 0;
/**
* Constructor that takes a maximum page size.
*
* @param pageSize Maximum result size.
*/
public PageFilter(final long pageSize) {
Preconditions.checkArgument(pageSize >= 0, "must be positive %s", pageSize);
this.pageSize = pageSize;
}
public long getPageSize() {
return pageSize;
}
public boolean filterAllRemaining() {
return this.rowsAccepted >= this.pageSize;
}
public boolean filterRow() {
this.rowsAccepted++;
return this.rowsAccepted > this.pageSize;
}
public boolean hasFilterRow() {
return true;
}
public static Filter createFilterFromArguments(ArrayList<byte []> filterArguments) {
Preconditions.checkArgument(filterArguments.size() == 1,
"Expected 1 but got: %s", filterArguments.size());
long pageSize = ParseFilter.convertByteArrayToLong(filterArguments.get(0));
return new PageFilter(pageSize);
}
/**
* @return The filter serialized using pb
*/
public byte [] toByteArray() {
FilterProtos.PageFilter.Builder builder =
FilterProtos.PageFilter.newBuilder();
builder.setPageSize(this.pageSize);
return builder.build().toByteArray();
}
/**
* @param pbBytes A pb serialized {@link PageFilter} instance
* @return An instance of {@link PageFilter} made from <code>bytes</code>
* @throws DeserializationException
* @see #toByteArray
*/
public static PageFilter parseFrom(final byte [] pbBytes)
throws DeserializationException {
FilterProtos.PageFilter proto;
try {
proto = FilterProtos.PageFilter.parseFrom(pbBytes);
} catch (InvalidProtocolBufferException e) {
throw new DeserializationException(e);
}
return new PageFilter(proto.getPageSize());
}
/**
* @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 PageFilter)) return false;
PageFilter other = (PageFilter)o;
return this.getPageSize() == other.getPageSize();
}
@Override
public String toString() {
return this.getClass().getSimpleName() + " " + this.pageSize;
}
}