[Phpmyadmin-devel] Innodb and row exact count

[Madhura Jayaratne]

On Sat, Jul 27, 2013 at 4:36 PM, Marc Delisle <marc at infomarc.info> wrote:

> Le 2013-07-27 07:04, Marc Delisle a écrit :
> > Le 2013-07-27 07:02, Madhura Jayaratne a écrit :
> >>
> >>
> >>
> >> On Thu, Jul 25, 2013 at 1:39 AM, Marc Delisle <marc at infomarc.info
> >> <mailto:marc at infomarc.info>> wrote:
> >>
> >>      Le 2013-06-12 17:04, Marc Delisle a écrit :
> >>       > Le 2013-06-12 03:23, Michal Čihař a écrit :
> >>       >> Hi
> >>       >>
> >>       >> Dne Tue, 11 Jun 2013 13:20:44 -0400
> >>       >> Marc Delisle <marc at infomarc.info <mailto:marc at infomarc.info>>
> >>      napsal(a):
> >>       >>
> >>       >>> I don't find a winning solution so I'm seeking for advice. In
> >>      this bug
> >>       >>> report [0], we see that it's annoying to have incorrect page
> >>      navigation
> >>       >>> (page selector and arrows) for InnoDB.
> >>       >>>
> >>       >>> However, when I apply my proposed patch (which forces an exact
> >>      count in
> >>       >>> sql.php), I see delays for larger InnoDB tables.
> >>       >>>
> >>       >>> For example, on MySQL 5.5.31, the first time I browse a table
> >>      having one
> >>       >>> million rows, I wait for 9 seconds. I tried with 0.5 million
> >>      and it was
> >>       >>> about 5 seconds. A few minutes afterwards, even after closing
> the
> >>       >>> browser, my big table starts to display in two seconds.
> >>       >>>
> >>       >>> I tend to find these delays acceptable and I propose to apply
> >>      my patch.
> >>       >>
> >>       >> I agree this is acceptable and agree with the patch for 4.0.4.
> >>       >>
> >>       >> For 4.1 I'd go even further - drop MaxExactCount and use only
> >>      not exact
> >>       >> counts on overview pages and count properly when browsing.
> >>       >
> >>       > Thanks, I'll have a look at this suggestion for 4.1.
> >>       >
> >>       >
> >>
> >>      Hmmm, I think we have a problem with exact counting, see
> >>      https://sourceforge.net/p/phpmyadmin/bugs/4027/
> >>
> >>      It's true that 750 M rows is a lot of rows...
> >>
> >> Would it make things too slow to get the rough count first and then get
> >> the exact count if the rough counts is less than some defined threshold?
>
> (The title of bug #4027 is "$cfg['MaxExactCount'] is ignored when
> BROWSING is back")
> >
> > That's exactly the goal of the MaxExactCount configuration directive,
> > and I think it could be applied here as well.
> >
> > Would not be too slow, as the rough count is very quick.
> >
>
My bad.

So I think it's best to use $cfg['MaxExactCount'] in browsing as well.
However IMO, its default value being 0 would break its purpose.

-- 
Thanks and Regards,

Madhura Jayaratne
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