mysql的extents

歸隱鄉(xiāng)村

一直以為mysqld餓extents的大小是固定的1M,今天發(fā)現(xiàn)不是這樣的。

lyhabc

每個extent是1MB


page，頁
最小I/O單位，16KB，5.6版本起可自定義page size  innodb_page_size



extent，區(qū)
空間管理單位
每個extent總是1MB，由64個page組成
如果page size是8KB的話，則由128個page組成


segment，段
對象單位，例如rollback seg，undo seg，data seg，index seg等
每個segement由N個extent以及32個零散page組成
segment最小以extent為單位擴展


tablespace，表空間
表存儲對象
每個tablespace都至少包含2種segement（葉子/非葉子 page file segment）

action08

那你今天發(fā)現(xiàn)了什么意外收獲？？謝謝分享一下哈

歸隱鄉(xiāng)村

5.6上是你說的這樣子的。5.7上變了。是我沒描述清楚問題。

5.6中
Pages, Extents, Segments, and Tablespaces
Each tablespace consists of database pages. Every tablespace in a MySQL instance has the same page size. By default, all tablespaces have a page size of 16KB; you can reduce the page size to 8KB or 4KB by specifying the innodb_page_size [1634] option when you create the MySQL instance.
The pages are grouped into extents of size 1MB (64 consecutive 16KB pages, or 128 8KB pages, or 256 4KB pages). The “files” inside a tablespace are called segments in InnoDB. (These segments are different from the rollback segment, which actually contains many tablespace segments.)

5.7中
14.9.2 File Space Management
Pages, Extents, Segments, and Tablespaces
Each tablespace consists of database pages. Every tablespace in a MySQL instance has the same page size. By default, all tablespaces have a page size of 16KB; you can reduce the page size to 8KB or 4KB by specifying the innodb_page_size option when you create the MySQL instance. As of MySQL 5.7.6, you can also increase the page size to 32KB or 64KB. For more information, refer to the innodb_page_size documentation.

The pages are grouped into extents of size 1MB for pages up to 16KB in size (64 consecutive 16KB pages, or 128 8KB pages, or 256 4KB pages). For a page size of 32KB, extent size is 2MB. For page size of 64KB, extent size is 4MB.


回復(fù) 2# lyhabc