MySQL Bugs: #81610: Improve documentation on innodb_log_compressed

Bug #81610	Improve documentation on innodb_log_compressed_pages
Submitted:	26 May 2016 11:05	Modified:	22 Sep 2016 15:02
Reporter:	Simon Mudd (OCA)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S4 (Feature request)
Version:	5.7	OS:	Any
Assigned to:		CPU Architecture:	Any

Description:
While looking for some documentation on the setting above at
https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_log_compresse... I find that the description is not complete enough to understand the consequences of changing the value from its default.

It would be useful to have a longer, more complete description of what the change does, why you might want to set it and how you might be able any improvement etc. 

https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-diskio.html makes no mention of this setting.

How to repeat:
See above.

My understanding is that:
* if using compressed innodb pages changes to the full page are logged. If this is the case (though strictly speaking it may not be necessary) then avoiding these writes may be useful. So on busy systems there may be some gain to be had.
* if compressed pages are not used then changing the setting will make no difference.
* this may affect upgrades between versions if compression changes

Suggested fix:
* Improve the documentation of this setting
* Give an indication of how the effect of the change may be measured
* Reference this parameter in optimizing-innodb-diskio.html if appropriate

Related: bug#81611

Hello Simon Mudd,

Thank you for the feedback!

Thanks,
Umesh

Posted by developer:
 
The following content has been updated: 

https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_log_compresse...
https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-diskio.html
https://dev.mysql.com/doc/refman/5.7/en/innodb-performance-compression-oltp.html

Changes should appear online soon. Thank you for the bug report.

Posted by developer:
 
Inaam Rana Blog: 
https://blogs.oracle.com/mysqlinnodb/entry/innodb_compression_improvements_in_mysql