Comments on: What are MySQL’s deleted temp files?

By: Cédric

Cédric — Thu, 13 Sep 2012 13:44:18 +0000

Yes, temporary files are created by MySQL for various reasons but what I don’t explain is why the files sometimes have a “deleted” status.

By: Xaprb

Xaprb — Thu, 13 Sep 2012 13:39:43 +0000

Axel: right, I know about tmpfile — the question was not what the files are, but what MySQL is using them for, and the naming convention provides a hint (all of InnoDB’s start with ib, etc). Though I’ve seen somewhere (I forget where) that ML files are for row-based-replication binlog cache files and MY files are for statement-based, and I’ve seen ML files contain statement-based-replication binlog caches :-)

By: XL

XL — Thu, 13 Sep 2012 12:04:18 +0000

MySQL creates almost any temporary file (that is: anything except materialezed temporary tables) in that manner, which is quite common in *NIX systems (man tmpfile)

I guess by far the most and biggest temp files will be created by the file sort algorithm. See http://dev.mysql.com/doc/internals/en/filesort.html

By: Jervin R

Jervin R — Thu, 13 Sep 2012 11:23:15 +0000

The ML* files are described here http://www.mysqlperformanceblog.com/2012/08/06/filling-the-tmp-partition-with-persistent-connections/ :)

By: Cédric

Cédric — Thu, 13 Sep 2012 09:12:29 +0000

There is the same behavoir with the temporary files : http://www.mysqlplus.net/2012/05/07/temporary-file-behavior-and-lsof-save-life/