/*
*
* 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.IOException;
import java.util.ArrayList;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellComparator;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.shaded.protobuf.generated.FilterProtos;
import org.apache.hadoop.hbase.util.Bytes;
import com.google.common.base.Preconditions;
import org.apache.hadoop.hbase.shaded.com.google.protobuf.InvalidProtocolBufferException;
import org.apache.hadoop.hbase.shaded.com.google.protobuf.UnsafeByteOperations;
/**
* 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. Only most recent versions are considered
* for pagination.
*/
@InterfaceAudience.Public
public class ColumnPaginationFilter extends FilterBase {
private int limit = 0;
private int offset = -1;
private byte[] columnOffset = null;
private int count = 0;
/**
* Initializes filter with an integer offset and limit. The offset is arrived at
* scanning sequentially and skipping entries. @limit number of columns are
* then retrieved. If multiple column families are involved, the columns may be spread
* across them.
*
* @param limit Max number of columns to return.
* @param offset The integer offset where to start pagination.
*/
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;
}
/**
* Initializes filter with a string/bookmark based offset and limit. The offset is arrived
* at, by seeking to it using scanner hints. If multiple column families are involved,
* pagination starts at the first column family which contains @columnOffset. Columns are
* then retrieved sequentially upto @limit number of columns which maybe spread across
* multiple column families, depending on how the scan is setup.
*
* @param limit Max number of columns to return.
* @param columnOffset The string/bookmark offset on where to start pagination.
*/
public ColumnPaginationFilter(final int limit, final byte[] columnOffset) {
Preconditions.checkArgument(limit >= 0, "limit must be positive %s", limit);
Preconditions.checkArgument(columnOffset != null,
"columnOffset must be non-null %s",
columnOffset);
this.limit = limit;
this.columnOffset = columnOffset;
}
/**
* @return limit
*/
public int getLimit() {
return limit;
}
/**
* @return offset
*/
public int getOffset() {
return offset;
}
/**
* @return columnOffset
*/
public byte[] getColumnOffset() {
return columnOffset;
}
@Override
public boolean filterRowKey(Cell cell) throws IOException {
// Impl in FilterBase might do unnecessary copy for Off heap backed Cells.
return false;
}
@Override
public ReturnCode filterKeyValue(Cell v)
{
if (columnOffset != null) {
if (count >= limit) {
return ReturnCode.NEXT_ROW;
}
int cmp = 0;
// Only compare if no KV's have been seen so far.
if (count == 0) {
cmp = CellComparator.compareQualifiers(v, this.columnOffset, 0, this.columnOffset.length);
}
if (cmp < 0) {
return ReturnCode.SEEK_NEXT_USING_HINT;
} else {
count++;
return ReturnCode.INCLUDE_AND_NEXT_COL;
}
} else {
if (count >= offset + limit) {
return ReturnCode.NEXT_ROW;
}
ReturnCode code = count < offset ? ReturnCode.NEXT_COL :
ReturnCode.INCLUDE_AND_NEXT_COL;
count++;
return code;
}
}
@Override
public Cell getNextCellHint(Cell cell) {
return CellUtil.createFirstOnRowCol(cell, columnOffset, 0, columnOffset.length);
}
@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);
}
/**
* @return The filter serialized using pb
*/
public byte [] toByteArray() {
FilterProtos.ColumnPaginationFilter.Builder builder =
FilterProtos.ColumnPaginationFilter.newBuilder();
builder.setLimit(this.limit);
if (this.offset >= 0) {
builder.setOffset(this.offset);
}
if (this.columnOffset != null) {
builder.setColumnOffset(UnsafeByteOperations.unsafeWrap(this.columnOffset));
}
return builder.build().toByteArray();
}
/**
* @param pbBytes A pb serialized {@link ColumnPaginationFilter} instance
* @return An instance of {@link ColumnPaginationFilter} made from <code>bytes</code>
* @throws DeserializationException
* @see #toByteArray
*/
public static ColumnPaginationFilter parseFrom(final byte [] pbBytes)
throws DeserializationException {
FilterProtos.ColumnPaginationFilter proto;
try {
proto = FilterProtos.ColumnPaginationFilter.parseFrom(pbBytes);
} catch (InvalidProtocolBufferException e) {
throw new DeserializationException(e);
}
if (proto.hasColumnOffset()) {
return new ColumnPaginationFilter(proto.getLimit(),
proto.getColumnOffset().toByteArray());
}
return new ColumnPaginationFilter(proto.getLimit(),proto.getOffset());
}
/**
* @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 ColumnPaginationFilter)) return false;
ColumnPaginationFilter other = (ColumnPaginationFilter)o;
if (this.columnOffset != null) {
return this.getLimit() == other.getLimit() &&
Bytes.equals(this.getColumnOffset(), other.getColumnOffset());
}
return this.getLimit() == other.getLimit() && this.getOffset() == other.getOffset();
}
@Override
public String toString() {
if (this.columnOffset != null) {
return (this.getClass().getSimpleName() + "(" + this.limit + ", " +
Bytes.toStringBinary(this.columnOffset) + ")");
}
return String.format("%s (%d, %d)", this.getClass().getSimpleName(),
this.limit, this.offset);
}
}