[Phpmyadmin-devel] Performance improvements for servers having large number of databases

[Madhura Jayaratne]

On Wed, Nov 5, 2014 at 8:41 AM, Marc Delisle <marc at infomarc.info> wrote:

> Madhura Jayaratne a écrit :
> > On Mon, Nov 3, 2014 at 10:31 AM, Madhura Jayaratne <madhura.cj at gmail.com
> >
> > wrote:
> >
> >>
> >> On Mon, Nov 3, 2014 at 10:08 AM, Marc Delisle <marc at infomarc.info>
> wrote:
> >>
> >>> Madhura Jayaratne a écrit :
> >>>> Hi all,
> >>>>
> >>>> Today morning I spent some time testing the performance improvements
> >>> that
> >>>> were done for the servers having a large number of databases.
> >>>>
> >>>> My setup has about 5000 databases grouped in to database groups of 20
> >>>> databases. Navigation items at first level [1] is limited to 50
> meaning
> >>>> that about 1000 databases are loaded in the initial page of
> navigation.
> >>>>
> >>>> While loading the initial page,
> >>>> QA_4_2: 1008 queries executed 1011 times in 1.00407 s
> >>>> master: 12 queries executed 17 times in 0.51211s
> >>>>
> >>>> Even though master is about 2 times faster in terms of the query
> >>> execution
> >>>> time, the overall time to load the page is dominated by the time taken
> >>> to
> >>>> render 1000 nodes in navigation, which is about 8s for master and 11s
> >>> for
> >>>> QA_4_2.
> >>>>
> >>>> However the rendering time can be significantly improved by setting
> [1]
> >>> to
> >>>> a lower value, which currently defaults to 250. If I remember right,
> >>> this
> >>>> directive was set to a higher value to prevent navigation from having
> >>> extra
> >>>> spaces below [2]. Since this issue is no longer there (now when [1] is
> >>> set
> >>>> to, say 50, 50 databases or database groups are displayed) I suggest
> to
> >>> set
> >>>> [1] to a lower value.
> >>>>
> >>>>
> >>>> [1]
> >>>>
> >>>
> http://docs.phpmyadmin.net/en/latest/config.html#cfg_FirstLevelNavigationItems
> >>>> [2] https://sourceforge.net/p/phpmyadmin/mailman/message/30077320/
> >>> Hi Madhura,
> >>> Good idea.
> >>>
> >> I've set this to 25, which seemed to fit to the screen without showing
> >> scroll bars.
> >>
> >> --
> >> Thanks and Regards,
> >>
> >> Madhura Jayaratne
> >>
> >>
> > Now, that I got access to the test server of Ann + J.M. with I could test
> > the performance improvements done so far. Test server has more than 25000
> > databases.
> >
> > For a privileged user:
> > As also reported by Marc, signing in take about 7-8 seconds while
> > navigating to pages in navigation now takes only about 3-4 seconds. This
> is
> > due to lower default value for 'FirstLevelNavigationItems' configuration.
> > Expanding a database in navigation also takes about 3 seconds. Similarly
> > going into a database (viewing database structure page) took about 4-5
> > seconds.
> >
> > Other database level operation such as searching in a database, viewing
> > routines, events, triggers, going in to the designer took acceptable
> times.
> > Similarly table level operations such as browsing, grid editing, editing,
> > searching, inserting were also at an acceptable level. Editing the table
> > structure which took some long time now takes only 3 - 5 seconds
> depending
> > on the number of fields.
> >
> > Database filters work normally as well.
> >
> > For an unprivileged user:
> > Login in and other operations take staggering long times for an
> > unprivileged user. I tried viewing the list of databases (just 2,
> > information_schema and one database by the username) for such user with
> the
> > mysql console. Both SHOW DATABASES as well as SELECT  schema_name FROM
> > information_schema.schemata takes about 48 seconds.
> >
> > On a positive note SHOW DATABASES LIKE '<username>%'; takes just a
> fraction
> > of seconds. However only for the users at large hosting providers we can
> > use such a query to retrieve the database list. If we are to take
> advantage
> > of this, we probably will have a add a new configuration to indicate that
> > unprivileged users are connecting to a particular installation of
> > phpMyAdmin and hosting providers will have to use two installations, one
> > for unprivileged users and one for privileged users.
> >
> > I am working on such a solution today and I will be able to test it by
> > tonight or tomorrow morning. I would appreciate your feedback on whether
> > such a solution is practical.
>
> I bet that hosting providers would remind us that before version 4.2,
> they were using a single installation for both kind of users.
>
> Also, using
> SHOW DATABASES LIKE '<username>%';
>
> is making an assumption about how the rights are assigned, and might not
> work in all cases.
>
> Found a better way to handle this.
By analyzing GRANTs, it is possible to figure out whether the user has
global privileges or if not the set of databases or wildcards the user has
permissions. These databases or wildcards can then be uses with SHOW
DATABASES LIKE to retrieve databases.

I implemented this on the master and this gives reasonable performance for
non privileged users on the test server.

-- 
Thanks and Regards,

Madhura Jayaratne
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