Re: Tuning MySQL 4.0.20 for large full table scans

[Matt W]

Hi Dan,

----- Original Message -----
From: "Dan Nelson"
Sent: Thursday, June 03, 2004 12:34 PM
Subject: Re: Tuning MySQL 4.0.20 for large full table scans

[snip]

> > Not sure what can be done about making it not go straight to tmpdir
> > with a BLOB column in the SELECT clause, though.  Probably nothing,
> > in 4.0.
>
> Do you actually see a temp file being created?  With tmp_table_size set
> to 2gb, it shouldn't have to go to disk.  Some more interesting data
> would be the State column from "show processlist" during the query,
> every 10 seconds or so.

Currently, temporary tables with TEXT/BLOB columns are always created on
disk because HEAP tables don't support variable-length rows.  I think this
limitation will be lifted in 5.0 or 5.1.

For the original poster, maybe this is one of the times that a RAM disk
could be useful for MySQL's tmpdir.


Matt