Re: Performance issues afre upgrading to 5.7

[Øystein Grøvlen]

Peter Brawley Wrote:
-------------------------------------------------------
> Pretty obviously it's a bug they're having
> difficulty with.
>
> A workaround: pick off the rows column value from
> ...
>
> EXPLAIN SELECT COUNT(PKcolname) FROM tblname USE
> INDEX (PRIMARY)

Hi,

The problem in this case s actually that the primary index is used for the counting instead of another index. Hence, USE INDEX (PRIMARY) would be counter productive. As I wrote in another answer, from 5.7.18, it will be possible to FORCE a specific index to be used.

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway