com.alibaba.innodb.java.reader.page.index

类 OverflowPagePointer

java.lang.Object

com.alibaba.innodb.java.reader.page.index.OverflowPagePointer

public class OverflowPagePointer
extends Object

https://mysqlserverteam.com/externally-stored-fields-in-innodb/

https://www.itread01.com/content/1546184536.html

When a BLOB field is stored externally, a BLOB reference is stored in the clustered index record. The BLOB reference will be stored after the BLOB prefix, if any. This BLOB reference is 20 bytes, and it contains the following information: 當一個BLOB field被儲存在external pages時，會在index pages中儲存該BLOB field的BLOB reference(指示該BLOB的 size,external page位置等元資料資訊)。如果表的row format為COMPACT或者REDUNDANT，那麼BLOB reference儲存在 BLOB prefix之後。BLOB reference 佔用20 bytes空間，包含如下資訊：

• The space identifier (4 bytes) 表空間資訊(下圖中的Space ID部分)
• The page number where the first page of the BLOB is stored (4 bytes) 儲存BLOB field的起始 page號(下圖中的Page Number部分)
• The offset of the BLOB header within that page (4 bytes) 起始page中 BLOB header 的位移量(下圖中的Offset)
• The total size of the BLOB data (8 bytes) 該BLOB 的 total size(除了上面三個以外的剩餘部分)

Even though 8 bytes are available to store the total size of the BLOB data, only the last 4 bytes are actually used. This means that within InnoDB, the maximum size of a single BLOB field is currently 4GB. 儘管上面我們提到有8 bytes的空間可以用來儲存BLOB size資訊，但是實際上僅有 4 bytes空間可以真正用來儲存BLOB size 資訊。這就意味著，innodb中可以儲存的最大 BLOB field size 是4 GB(4 bytes=32 bit ,2^32=4GB)

作者:

xu.zx

构造器概要

构造器

构造器和说明
OverflowPagePointer()

方法概要

限定符和类型	方法和说明
static OverflowPagePointer	fromSlice(SliceInput input)

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造器详细资料

OverflowPagePointer

public OverflowPagePointer()

方法详细资料

fromSlice

public static OverflowPagePointer fromSlice(SliceInput input)