Multiple Rollback Segments

In Percona Server 5.1, an improvement was provided for write-intensive workloads that allowed multiple rollback segments to be used. It has been removed from Percona Server 5.5.11-20.2 because an equivalent variable, innodb_rollback_segment, has been implemented in MySQL 5.5, and so the MySQL 5.5 implementation is available in Percona Server 5.5.

Percona Server, in addition to the upstream multiple rollback segment implementation, provides the additonal Information Schema table: INFORMATION_SCHEMA.INNODB_RSEG.

INFORMATION_SCHEMA Tables

This feature provides the following table:

table INFORMATION_SCHEMA.INNODB_RSEG

Columns:

• rseg_id – rollback segment id
• space_id – space where the segment placed
• zip_size – compressed page size in bytes if compressed otherwise 0
• page_no – page number of the segment header
• max_size – max size in pages
• curr_size – current size in pages

This table shows information about all the rollback segments (the default segment and the extra segments).

Here is an example of output with innodb_extra_rsegments = 8

mysql> select * from information_schema.innodb_rseg;
+---------+----------+----------+---------+------------+-----------+
| rseg_id | space_id | zip_size | page_no | max_size   | curr_size |
+---------+----------+----------+---------+------------+-----------+
|       0 |        0 |        0 |       6 | 4294967294 |         1 |
|       1 |        0 |        0 |      13 | 4294967294 |         2 |
|       2 |        0 |        0 |      14 | 4294967294 |         1 |
|       3 |        0 |        0 |      15 | 4294967294 |         1 |
|       4 |        0 |        0 |      16 | 4294967294 |         1 |
|       5 |        0 |        0 |      17 | 4294967294 |         1 |
|       6 |        0 |        0 |      18 | 4294967294 |         1 |
|       7 |        0 |        0 |      19 | 4294967294 |         1 |
|       8 |        0 |        0 |      20 | 4294967294 |         1 |
+---------+----------+----------+---------+------------+-----------+
9 rows in set (0.00 sec)