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From:Tompkins Neil Date:October 11 2011 6:38pm
Subject:Re: Index question
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Thanks for the information.  One final question in what ways should we use
EXPLAIN EXTENDED statement to help improve our query performance.

On Tue, Oct 11, 2011 at 2:51 PM, Johan De Meersman <vegivamp@stripped>wrote:

> ----- Original Message -----
> > From: "Rik Wasmus" <rik@stripped>
> >
> > Depends on the data and usage, but probably I'd go for a index(a,b) &
> > index(b,a) if reads heavily outnumber writes.  As index(a) is covered
> > by index(a,b), and index(b) by index(b,a), we don't need to add those,
> > which saves time on modifications.
>
> I'm trying to think of a scenario where index(a) would be beneficial in the
> presence of index(a,b). If both are available, and all else being equal,
> it's likely that the parser will pick the simplest index; but I can't see it
> having a major impact.
>
> Any full prefix of a combined index may be used; so afaik a separate index
> on any full prefix is a waste of diskspace and cycles.
>
> The net conclusion, Neil, is that you actually have to know what you're
> doing :-) Take the time to read the online documentation on mysql.com,
> it's pretty good.
>
>
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Thread
Index questionAlex Schaft11 Oct
  • Re: Index questionJohan De Meersman11 Oct
    • Re: Index questionNeil Tompkins11 Oct
      • Re: Index questionRik Wasmus11 Oct
        • Re: Index questionAlex Schaft11 Oct
          • Re: Index questionAlex Schaft11 Oct
          • Re: Index questionRik Wasmus11 Oct
            • Re: Index questionNeil Tompkins11 Oct
              • Re: Index questionRik Wasmus11 Oct
                • Re: Index questionJohan De Meersman11 Oct
                  • Re: Index questionTompkins Neil11 Oct
                    • Re: Index questionJohan De Meersman12 Oct
  • Re: Index questionArthur Fuller11 Oct