Re: MySQL index question

Frederick Cheung
Tue, 20 Jul 2010 14:37:12 -0000

On Jul 20, 3:12 pm, "Jeffrey L. Taylor"
<r...-f/t7CGFWhwGcvWdFBKKxig@public.gmane.org>
wrote:
> I am trying to speed up some DB operations and perhaps have gone overboard
> with indexes.  Does MySQL usually use only one index per query and simply
> match keys on the results of the indexed first part?  For example:

one one index will be used per table

>
> DELETE FROM tokens WHERE 6813946236211560448 <= fnv AND fnv <
6818449835838930944 AND updated_at<''2010-06-20 14:08:55''
AND occurrences=0;
>
> If I understand correctly from the output of:
>
> EXPLAIN SELECT * FROM tokens WHERE 6813946236211560448 <= fnv AND fnv
< 6818449835838930944 AND updated_at<''2010-06-20
14:08:55'' AND occurrences=0;
>
> only the index on fnv is used (there are indexes on updated_at and
> occurrences).
>
> Is this correct?

hard to say without said output :-)

Fred
>
> TIA,
>   Jeffrey