| /** |
| * 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; |
| |
| import java.nio.ByteBuffer; |
| |
| import org.apache.yetus.audience.InterfaceAudience; |
| |
| /** |
| * This class is a server side extension to the {@link Cell} interface. It is used when the |
| * Cell is backed by a {@link ByteBuffer}: i.e. <code>cell instanceof ByteBufferedCell</code>. |
| * |
| * <p>This class has getters for the row, column family, column qualifier, value and tags hosting |
| * ByteBuffers. It also has getters of the *position* within a ByteBuffer where these |
| * field bytes begin. These are needed because a single ByteBuffer may back one or many Cell |
| * instances -- it depends on the implementation -- so the ByteBuffer position as returned by |
| * {@link ByteBuffer#arrayOffset()} cannot be relied upon. Also, do not confuse these position |
| * methods with the getXXXOffset methods from the super Interface, {@link Cell}; dependent up on |
| * implementation, the Cell getXXXOffset methods can return the same value as a call to its |
| * equivalent position method from below BUT they can also stray; if a ByteBufferedCell, use the |
| * below position methods to find where a field begins. |
| * |
| * <p>Use the getXXXLength methods from Cell to find a fields length. |
| * |
| * <p>A Cell object can be of this type only on the server side. |
| * |
| * <p>WARNING: If a Cell is backed by an offheap ByteBuffer, any call to getXXXArray() will result |
| * in a temporary byte array creation and a bytes copy. Avoid these allocations by using the |
| * appropriate Cell access server-side: i.e. ByteBufferedCell when backed by a ByteBuffer and Cell |
| * when it is not. |
| */ |
| /* |
| * Even though all the methods are abstract, ByteBufferExtendedCell is not made to be an interface |
| * with intent. In CellComparator compare method, we have instance of check to decide whether to |
| * use getXXXArray() or getXXXByteBuffer(). This is a very hot method in read and write paths. |
| * if (left instanceof ByteBufferExtendedCell && right instanceof ByteBufferExtendedCell) { |
| .... |
| } |
| if (left instanceof ByteBufferExtendedCell) { |
| .... |
| } |
| if (right instanceof ByteBufferExtendedCell) { |
| .... |
| } |
| return Bytes.compareTo(left.getRowArray(), left.getRowOffset(), left.getRowLength(), |
| right.getRowArray(), right.getRowOffset(), right.getRowLength()); |
| * We did JMH micro benchmark tests with both left and right cells as ByteBufferExtendedCell, one |
| * only ByteBufferExtendedCell and both as Cells. This is compared against JMH results on compare |
| * logic with out any instance of checks. We noticed that if ByteBufferExtendedCell is an |
| * interface, the benchmark result seems to be very bad for case of both right and left are Cell |
| * only (Not ByteBufferExtendedCell). When ByteBufferExtendedCell is an abstract class all 4 |
| * possible cases giving almost similar performance number compared with compare logic with no |
| * instance of checks. |
| */ |
| @InterfaceAudience.Private |
| public abstract class ByteBufferExtendedCell implements ExtendedCell { |
| /** |
| * @return The {@link ByteBuffer} containing the row bytes. |
| */ |
| public abstract ByteBuffer getRowByteBuffer(); |
| |
| /** |
| * @return Position in the {@link ByteBuffer} where row bytes start |
| */ |
| public abstract int getRowPosition(); |
| |
| /** |
| * @return The {@link ByteBuffer} containing the column family bytes. |
| */ |
| public abstract ByteBuffer getFamilyByteBuffer(); |
| |
| /** |
| * @return Position in the {@link ByteBuffer} where column family bytes start |
| */ |
| public abstract int getFamilyPosition(); |
| |
| /** |
| * @return The {@link ByteBuffer} containing the column qualifier bytes. |
| */ |
| public abstract ByteBuffer getQualifierByteBuffer(); |
| |
| /** |
| * @return Position in the {@link ByteBuffer} where column qualifier bytes start |
| */ |
| public abstract int getQualifierPosition(); |
| |
| /** |
| * @return The {@link ByteBuffer} containing the value bytes. |
| */ |
| public abstract ByteBuffer getValueByteBuffer(); |
| |
| /** |
| * @return Position in the {@link ByteBuffer} where value bytes start |
| */ |
| public abstract int getValuePosition(); |
| |
| /** |
| * @return The {@link ByteBuffer} containing the tag bytes. |
| */ |
| public abstract ByteBuffer getTagsByteBuffer(); |
| |
| /** |
| * @return Position in the {@link ByteBuffer} where tag bytes start |
| */ |
| public abstract int getTagsPosition(); |
| } |