On Wed, Jan 31, 2001 at 09:12:05AM +0000, Basil Hussain wrote:
>
> I think I understand this now. The table_cache is the maximum number
> of tables MySQL can keep open all the time. If your table_cache is
> lower than the actual number of tables in use (in my case 64 versus
> 70), then when a table that is not already open needs to be used,
> MySQL must open it, and so increments the Opened_tables status
> variable. In an ideal world, Opened_tables would be nil (or very
> low), as MySQL would already have all the tables open, yes?
Yes.
> > Queries that require a full table scan (those which don't or can't
> > use indexes). "Sequential scans" can mean "full table scans".
>
> So, basically, a large record_buffer is only useful if your queries
> operate in a non-efficient fashion by not using indexes? I try to
> optimise all of my queries, and I'm pretty sure that reducing it to
> something like 4Mb would be alright.
Basically, yes. But there are cases in which a full table scan is the
fastest way to do something, and MySQL may decide to do that.
> > You didn't mention the key_buffer. If configured well, you can get a
> > great performance boost from it.
>
> My key_buffer is currently at 128Mb, but I'm considering upping that
> to 192Mb or maybe even 256Mb. Probably the former, as I don't have
> tables with hundereds of thousands of records to contend with.
Sounds like you've got a good understanding of what's going on
now. Good luck. :-)
Jeremy
--
Jeremy D. Zawodny, <[EMAIL PROTECTED]>
Technical Yahoo - Yahoo Finance
Desk: (408) 328-7878 Fax: (408) 530-5454
Cell: (408) 439-9951
---------------------------------------------------------------------
Before posting, please check:
http://www.mysql.com/manual.php (the manual)
http://lists.mysql.com/ (the list archive)
To request this thread, e-mail <[EMAIL PROTECTED]>
To unsubscribe, e-mail <[EMAIL PROTECTED]>
Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
