MySQL Bugs: #42663: Table Cache rules do not work in 5.1 (table_cache -> table_open

Bug #42663	Table Cache rules do not work in 5.1 (table_cache -> table_open_cache)
Submitted:	6 Feb 2009 20:10	Modified:	24 Feb 2009 19:11
Reporter:	Andy Bang
Status:	Closed
Category:	Monitoring: Advisors/Rules	Severity:	S3 (Non-critical)
Version:	2.0.4.7141	OS:	Any
Assigned to:	Darren Oldag	Target Version:	2.0.5 maint release
Triage:	Needs Triage: D2 (Serious)

Description:
The "Table Cache Set Too Low For Startup" and "Table Cache Not Optimal" rules are not
supported on MySQL 5.1 because the table_cache system variable has been deprecated and
replaced with table_open_cache.

How to repeat:
Schedule the rules against a 5.0 server and you'll see they work.

Schedule them against a 5.1 server and you'll see you can't do it because table_cache is
no longer reported via SHOW GLOBAL VARIABLES.

Let's do a quick fix in the next 2.0 maintenance release, then think about the more
comprehensive fix for 2.1.

providing a one-off forwards compatibile translation of table_cache to 
table_open_cache when table_cache is not supported and table_open_cache is.
when more of these broken mysql variables come up, we should examine
this 'fall forward' mechanism to see if it can be made more robust to
additional changes and externalized.

patch pushed to trunk.  merge to 2.0 is pending.

patch pushed to 2.0 maintenance tree.  ready for build and qa test.

Verified fixed in service manager build 2.0.5.7144.

An entry was added to the 2.0.5 changelog:

The “Table Cache Set Too Low For Startup” and “Table Cache Not Optimal” rules
were not supported on MySQL 5.1 because the table_cache system variable was deprecated
and replaced with table_open_cache.

Verified fixed in service manager build 2.1.0.1011.

Closing since it has already been tested in 2.0.5 (see previous comments).

Related to Bug #49208