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From Abdel Hakim Deneche <adene...@maprtech.com>
Subject Re: Resetting an option
Date Thu, 17 Sep 2015 21:42:42 GMT
I am looking at the corresponding pull request:

https://github.com/apache/drill/pull/159

and I have a question I can't seem to find an answer in this discussion:

Let's say a user changes an option A both at the SESSION and SYSTEM level.
What happens when the users issues "ALTER SYSTEM RESET A", does it reset A
only at the SYSTEM level but leave it changed at the SESSION level, or do
we want it to reset both SESSION and SYSTEM levels of A ?



On Mon, Aug 10, 2015 at 3:24 PM, Abhishek Girish <agirish@mapr.com> wrote:

> A session level *set* operation, by definition, should override the
> corresponding system level option for the duration of the session.
>
> Going by that, I think, a *reset* operation should default it back to the
> value held by the system level option. If a user (say an admin) has updated
> the corresponding system option, the reverted value would be a custom,
> non-Drill-default value. And if not, the reverted value would be the
> Drill-default value. This would make it simpler to manage.
>
>
> On Mon, Aug 10, 2015 at 2:51 PM, Jason Altekruse <altekrusejason@gmail.com
> >
> wrote:
>
> > I don't know if I missed something, but the Postgres docs seem to
> indicate
> > that there is no equivalent to the concept of a SYSTEM option that exists
> > in Drill, which can be set with a query. Options can be set at server
> > startup, either in a configuration file or with a command line parameter
> > [2]. Once the server is running, it appears that the closest to our ALTER
> > SYSTEM statement would be the feature to set options at a user or
> database
> > level [2].
> >
> > Here is an excerpt from the docs on the DEFAULT option value: [1] -
> DEFAULT
> > can be written to specify resetting the parameter to its default value
> > (that is, whatever value it would have had if no SET had been executed in
> > the current session).
> >
> > We should probably just try it out to confirm, but this statement leads
> me
> > to believe that the option will return to the value set in the startup
> > config file/parameter or what was set at the user/database level, not the
> > system default. This is in agreement with my intuition on the issue, the
> > whole idea behind nesting these configurations, from Drill default to
> > System and then to Session would seem to be trying to provide users with
> > the safest environment possible.
> >
> > Setting something at the system level should only be done if the
> > administrator is certain that the non-standard option is a helpful
> > modification for the majority of their users. Thus users can choose to
> > override it, but their escape hatch should bring them back to the option
> > values given by their administrator, not Drill defaults.
> >
> > [1] http://www.postgresql.org/docs/9.2/static/sql-set.html
> > [2] http://www.postgresql.org/docs/9.2/static/config-setting.html
> >
> > On Mon, Aug 10, 2015 at 2:25 PM, Sudheesh Katkam <skatkam@maprtech.com>
> > wrote:
> >
> > > Correction: currently any user can SET or RESET an option for session
> and
> > > system.
> > >
> > > > On Aug 10, 2015, at 2:20 PM, Sudheesh Katkam <skatkam@maprtech.com>
> > > wrote:
> > > >
> > > > Hey y‘all,
> > > >
> > > > Re DRILL-1065 <https://issues.apache.org/jira/browse/DRILL-1065>,
at
> > > system level (ALTER system RESET …), resetting an option would mean
> > > changing the value to the default provided by Drill. But, at session
> > level
> > > (ALTER session RESET …), would resetting an option mean:
> > > > (a) changing the value to the default provided by Drill? or,
> > > > (b) changing the value to the system value, that an admin could’ve
> > > changed?
> > > >
> > > > (b) would not allow non-admin users to know what the default is
> > > (easily). However, for a given option, (a) would allow a non-admin user
> > to
> > > know what the default is (by resetting) and what the system setting is
> > > (from sys.options). Opinions?
> > > >
> > > > Thank you,
> > > > Sudheesh
> > >
> > >
> >
>



-- 

Abdelhakim Deneche

Software Engineer

  <http://www.mapr.com/>


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