percona-discussion team mailing list archive

[MARK CALLAGHAN <mdcallag@xxxxxxxxx>]

On Wed, May 27, 2009 at 8:47 AM, Dimitri <dimitri@xxxxxxx> wrote:
> On Wednesday 27 May 2009 @ 15:17, MARK CALLAGHAN wrote:
>> Dimitri made a comment about purge (non) performance in Innodb. I
>> ignore this most of the time as my workloads don't have many deletes
>
> I'd add it's also true for updates, so except if you're doing
> only inserts/selects - you're mostly concerned by this issue all
> the time..

That is true for updates to indexed columns. That is not true for
updates to non-indexed columns.
We have a lot of updates but most of them do not update indexed columns.

When an indexed column is updated, the pre-update index entry must be
removed (delete) and the post-update index entry must be added
(insert). When the non-indexed column is updated, the index entries
are not modified.

-- 
Mark Callaghan
mdcallag@xxxxxxxxx