[QGIS-Developer] Proposal: changing the behaviour of QgsFeatureRequest

[Alexis R.L.]

Greetings Mr. Dawson,

Thanks for the reply,

The tests that I did with the method in my PR was provider agnostic but
still entailed looping over every feature to do the check. Could you
provide idea or methods that could enable this behaviour in an API friendly
way?

Should I make a new iterator entirely or should I modify existing methods
and add a trigger like I tested in my PR?

Thanks!
Alexis Roy-Lizotte


Le dim. 28 avr. 2019 à 19:46, Nyall Dawson <nyall.dawson at gmail.com> a
écrit :

> On Sun, 28 Apr 2019 at 07:18, Alexis R.L. <alroyliz0 at gmail.com> wrote:
> >
> > Greetings Everyone,
> >
> > While working on my PR (9648) I noticed that expression filter and a
> list of feature IDs are both considered the same thing cannot be used as
> two filtering criteria.
> >
> > I am aware that the intent was to only have one element active to filter
> out features other than the rectangle(? might be wrong on that one).
> >
> > What I am wondering if it would be a good thing to have both co exist
> (mostly for my PR as of now). A simply way to do so would be to use the
> give feature ids as the list to iterate over and check for the expression
> if there is one.
>
> I also think this would be desirable. The tricky part (well, one
> tricky part -- feature iterators are low level stuff, lots of
> complexity there!) is avoiding any API breakage while adding new
> methods to handle your use case.
>
> The other (SUPER) tricky bit is that any change to feature requests
> usually requires accompanying changes to every vector data provider in
> order to keep consistent behaviour across all these providers. The
> same request should always give the same result, regardless of the
> actual underlying data provider. The consequence of this is that
> you'll need to be update the postgres, mssql, oracle, OGR, memory,
> spatialite, wfs, arcgis feature server, db2, and vector layer feature
> iterator code. You'll also need to add many new unit tests to cover
> all the changes to the different providers.
>
> Definitely not a trivial change! Don't let this put you off making it,
> but just be aware that this change would take even a QGIS core
> developer a week or more of work to implement.
>
> Nyall
>
>
>
> >
> > I assume that such a thing might be implemented without touching the
> current behaviour, otherwise one would have to remove either the expression
> or the IDs in some case when we want to override the current filtering
> method.
> >
> > Using multiple filtering method might be better than only forcing one
> and would provide more flexibility.
> >
> > As I have a PR that is related to this (
> https://github.com/qgis/QGIS/pull/9816 ) I would like to address this
> point in it and would like to have the discussion occur there as to the
> best way to implement such a thing without any breakage if people are not
> opposed to having only one filtering method in qgsfeaturerequest.
> >
> > Thanks and have a nice day!
> >
> > Alex
> > _______________________________________________
> > QGIS-Developer mailing list
> > QGIS-Developer at lists.osgeo.org
> > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer
> > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20190429/1cf8df4e/attachment.html>