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

Le 2013-07-27 08:20, Marc Delisle a écrit :

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.

See the discussion in https://github.com/phpmyadmin/phpmyadmin/pull/83

but this was before my change in 4.0.4.