Emergency

Multiple Rollback Segments

Warning

This feature has been removed in Percona Server 5.5.11-20.2 because an equivalent variable, innodb_rollback_segments, has been implemented in the upstream version.

In Percona Server 5.1, an improvement was provided for write-intensive workloads that allowed multiple rollback segments to be used.

Percona Server, in addition to the upstream multiple rollback segment implementation, provides the additional Information Schema table: 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)

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