MySQL Bugs: #5512: tmp_table_size limitation accross all processes

Bug #5512	tmp_table_size limitation accross all processes
Submitted:	10 Sep 2004 9:29	Modified:	3 Feb 2006 14:00
Reporter:	Martin Friebe (Gold Quality Contributor) (OCA)	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	MySQL Server	Severity:	S4 (Feature request)
Version:	4	OS:	Any (any)
Assigned to:		CPU Architecture:	Any

Description:
It would be usefull to have a tmp_table_size_combined variable, which allows to limit the amount of memory used by all tmp_tables at any given time.

This way you could increase tmp_table_size to whatever free memory you have (or half/third of it). Making the maximum use of your memory, if you run only one or two complex queries.
You still wouldn't need to worry, that in case you run more queries, you would need virtual memory and disk swapping. Mysql server would realize that it shouldn't allocate more memory and create disk based temporary tables for further queries.

How to repeat:
sorry not repeatable - feature request

Thank you for a feature request. We have one (ignored) parameter for the similar purpose, max_tmp_tables (http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html). So, I am not sure that this feature will be implemented in the foreseeable future.