On Sat, Jun 16, 2001 at 08:00:04PM -0500, Dan Nelson wrote:
> In the last episode (Jun 16), Jeremy Zawodny said:
> > Err, I forgot to mention that there's a "Using filesort" in the
> > output as well. That makes me believe it wants to write to disk (even
> > if there may be sufficient RAM).
>
> I'm not sure "Using filesort" actually means it is going to create a
> file. The code seems to print "filesort" whenever an ORDER BY is
> requested (sql_select.cc:536). Even the manual simply says "extra
> pass". Maybe it required a file-based table in an earlier version,
> but not anymore?
Based on testing, I've found that "Using filesort" appears only when
the number of records to be sorted is sufficiently high. The sort
order (asc/desc) doesn't matter. But take a "Using filesort" query,
put a "LIMIT 10" on the end of it and see if it goes away. It does for
me.
Hmmm...
Jeremy
--
Jeremy D. Zawodny, <[EMAIL PROTECTED]>
Technical Yahoo - Yahoo Finance
Desk: (408) 349-7878 Fax: (408) 349-5454 Cell: (408) 439-9951
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