001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase; 019 020import java.nio.ByteBuffer; 021import org.apache.yetus.audience.InterfaceAudience; 022 023/** 024 * This class is a server side extension to the {@link Cell} interface. It is used when the Cell is 025 * backed by a {@link ByteBuffer}: i.e. <code>cell instanceof ByteBufferedCell</code>. 026 * <p> 027 * This class has getters for the row, column family, column qualifier, value and tags hosting 028 * ByteBuffers. It also has getters of the *position* within a ByteBuffer where these field bytes 029 * begin. These are needed because a single ByteBuffer may back one or many Cell instances -- it 030 * depends on the implementation -- so the ByteBuffer position as returned by 031 * {@link ByteBuffer#arrayOffset()} cannot be relied upon. Also, do not confuse these position 032 * methods with the getXXXOffset methods from the super Interface, {@link Cell}; dependent up on 033 * implementation, the Cell getXXXOffset methods can return the same value as a call to its 034 * equivalent position method from below BUT they can also stray; if a ByteBufferedCell, use the 035 * below position methods to find where a field begins. 036 * <p> 037 * Use the getXXXLength methods from Cell to find a fields length. 038 * <p> 039 * A Cell object can be of this type only on the server side. 040 * <p> 041 * WARNING: If a Cell is backed by an offheap ByteBuffer, any call to getXXXArray() will result in a 042 * temporary byte array creation and a bytes copy. Avoid these allocations by using the appropriate 043 * Cell access server-side: i.e. ByteBufferedCell when backed by a ByteBuffer and Cell when it is 044 * not. 045 */ 046/* 047 * Even though all the methods are abstract, ByteBufferExtendedCell is not made to be an interface 048 * with intent. In CellComparator compare method, we have instance of check to decide whether to use 049 * getXXXArray() or getXXXByteBuffer(). This is a very hot method in read and write paths. if (left 050 * instanceof ByteBufferExtendedCell && right instanceof ByteBufferExtendedCell) { .... } if (left 051 * instanceof ByteBufferExtendedCell) { .... } if (right instanceof ByteBufferExtendedCell) { .... } 052 * return Bytes.compareTo(left.getRowArray(), left.getRowOffset(), left.getRowLength(), 053 * right.getRowArray(), right.getRowOffset(), right.getRowLength()); We did JMH micro benchmark 054 * tests with both left and right cells as ByteBufferExtendedCell, one only ByteBufferExtendedCell 055 * and both as Cells. This is compared against JMH results on compare logic with out any instance of 056 * checks. We noticed that if ByteBufferExtendedCell is an interface, the benchmark result seems to 057 * be very bad for case of both right and left are Cell only (Not ByteBufferExtendedCell). When 058 * ByteBufferExtendedCell is an abstract class all 4 possible cases giving almost similar 059 * performance number compared with compare logic with no instance of checks. 060 */ 061@InterfaceAudience.Private 062public abstract class ByteBufferExtendedCell implements ExtendedCell { 063 /** Returns The {@link ByteBuffer} containing the row bytes. */ 064 public abstract ByteBuffer getRowByteBuffer(); 065 066 /** Returns Position in the {@link ByteBuffer} where row bytes start */ 067 public abstract int getRowPosition(); 068 069 /** Returns The {@link ByteBuffer} containing the column family bytes. */ 070 public abstract ByteBuffer getFamilyByteBuffer(); 071 072 /** Returns Position in the {@link ByteBuffer} where column family bytes start */ 073 public abstract int getFamilyPosition(); 074 075 /** Returns The {@link ByteBuffer} containing the column qualifier bytes. */ 076 public abstract ByteBuffer getQualifierByteBuffer(); 077 078 /** Returns Position in the {@link ByteBuffer} where column qualifier bytes start */ 079 public abstract int getQualifierPosition(); 080 081 /** Returns The {@link ByteBuffer} containing the value bytes. */ 082 public abstract ByteBuffer getValueByteBuffer(); 083 084 /** Returns Position in the {@link ByteBuffer} where value bytes start */ 085 public abstract int getValuePosition(); 086 087 /** Returns The {@link ByteBuffer} containing the tag bytes. */ 088 public abstract ByteBuffer getTagsByteBuffer(); 089 090 /** Returns Position in the {@link ByteBuffer} where tag bytes start */ 091 public abstract int getTagsPosition(); 092}