On Fri, Jun 15, 2001 at 10:03:57PM -0500, Dan Nelson wrote:
>
> 30 seconds of cscope browsing on the mysql source shows the follwing
> comments right before calls to create_tmp_table():
>
> /* Create a tmp table if distinct or if the sort is too complicated */
> /* group data to new table */
>
> So I'd say Mysql will use temp tables on GROUP BY, DISTINCT, and
> probably ORDER BY queries that mysql cannot satisfy with the same
> index the optimizer picked.
>
> The need_tmp flag is passed to the describe function, so any query
> that requires a temp table should also have "Using temporary" in its
> explain plan.
Ah, thanks. The funny thing is that I *did* think to check the source
code for a different problem I ran into severl minutes later.
I'll have to poke at this some more. I just restarted with a 64MB
maximum and one of my more common queries is still "Using
temporary". I find it difficult to believe that I'm pulling enough
data to fill a 64MB table. The entire dataset is about 6 times that
size, and I know I'm not pulling even close to 1/6th of the data.
Hmm... More playing required...
Jeremy
--
Jeremy D. Zawodny, <[EMAIL PROTECTED]>
Technical Yahoo - Yahoo Finance
Desk: (408) 349-7878 Fax: (408) 349-5454 Cell: (408) 439-9951
MySQL 3.23.29: up 0 days, processed 2,435 queries (13/sec. avg)
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