Re: [Phpmyadmin-devel] Innodb and row exact count

Le 2013-07-27 07:25, Madhura Jayaratne a écrit :

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

Not necessarily. You see, the guy reporting bug #4027 was aware of this directive and can set it to an appropriate value.

In version 3.0.0 we had 20000 as a default value, not sure why we set it to 0 later.