[Kde-pim] [PATCH] Akonadi database optimization

[Volker Krause]

On Friday 30 July 2010 21:30:57 Tobias König wrote:
> Hej,
>
> as a proud user of KMail 4.5 I faced some performance problems lately which
> happened when entering a folder with many (in words 200) emails.
> In this case KMail was waiting nearly 30 seconds until it continued to show
> the emails in the message list.
>
> After some debugging, blaming nearly every component of the PIM stack
> (sorry Kevin, it was not the maildirresource ;)) and adding debug
> statements all over the places, mysqld was identified as the culprit. The
> problematic call was the fetch statement for all header payloads of all
> mails in the current folder. Just for fun I changed the fetch scope to
> FullPayload and to my suprise it was _faster_ then only fetching the
> headers.
> So the SQL query, which varies for both calls must be the issue.
> After some discussion with our MySQL-optimizer-Guru (aka milian) we came to
> the conclusion that the 'AND PimItemTable.id >= 1' condition in the
> statement leads to a performance bottleneck. The reason is that the >=
> operator will imply a so called range-join which has a bad performance.
> Fortunately this special condition is not really needed, because the 'id'
> column will always contain values >= 1 per definition. So we can just
> optimize this condition away and KMail 4.5 works as fast as it is supposed
> to do :)
>
> Attached is a patch that fixes QueryHelper to not add unnecessary >=
> conditions. Does somebody see any problems with it?

looks good to me, thanks!

regards
Volker
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