On Tue, Jun 1, 2010 at 8:40 AM, John G. Heim <jh...@math.wisc.edu> wrote: > On my db server, mysql has 2 gigabytes for temporary tables and yet its > creating 99% of temporary tables on disk. > > According to mysqltuner, 99% of temporary tables are created on disk.
Probably blobs: "Instances of BLOB or TEXT columns in the result of a query that is processed using a temporary table causes the server to use a table on disk rather than in memory because the MEMORY storage engine does not support those data types (see Section 7.5.10, “How MySQL Uses Internal Temporary Tables”). Use of disk incurs a performance penalty, so include BLOB or TEXT columns in the query result only if they are really needed. For example, avoid using SELECT *, which selects all columns. " >From http://dev.mysql.com/doc/refman/5.0/en/blob.html If you can get us a query, explain, and table/index info we may be able to help you more. Also, you might want to consider creating a ram disk so that filesorts that must be done on disk might be done inexpensively. -- Rob Wultsch wult...@gmail.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
