[Qgis-developer] Performance of QGIS expressions "attribute" and "get_feature"

[Stefan Ziegler]

Two postgres layers with an index on the fields.

Do I see some debug messages (when compiled with DEBUG)?

On Wed, Dec 30, 2015 at 9:27 PM, Nyall Dawson <nyall.dawson at gmail.com>
wrote:

> On 31 December 2015 at 06:18, Stefan Ziegler
> <stefan.ziegler.de at gmail.com> wrote:
> > Hi Nyall
> >
> > I compared 2.12 with current master. But I don't see an improvement.
> Opening
> > the attribute table takes around 10 seconds for layers with approx. 2000
> > features with one virtual field (with the attribute(get_feature())
> > expression). Rendering is also really slow when using rule based
> renderer on
> > the virtual field.
>
> What's the data source for each layer? If it's in a database (eg
> postgres), is there a suitable index on the joined field?
>
> Nyall
>
>
>
> >
> > regards
> > Stefan
> >
> > On Wed, Dec 30, 2015 at 7:22 PM, Nyall Dawson <nyall.dawson at gmail.com>
> > wrote:
> >>
> >>
> >> On 31 Dec 2015 2:01 AM, "Stefan Ziegler" <stefan.ziegler.de at gmail.com>
> >> wrote:
> >> >
> >> > Hi
> >> >
> >> > I add a virtual field to a layer with e.g. following expression
> >> >
> >> > attribute(get_feature('pnf_pnf','t_id',afrom),'year')
> >> >
> >> > This works really great. Then I'm using this new virtual field for
> >> > filtering the features in the rule based renderer. How does affect
> this the
> >> > rendering performance? It seems that it really slows down rendering
> even
> >> > with layers with only approx 600 features each.
> >> >
> >> > If so, can the speed improved with e.g. some to develop caching
> >> > mechanism?
> >>
> >> Try with the current master version - this should be MUCH faster now.
> I'd
> >> love to hear any feedback of how you find the changes improve (or don't
> >> improve!) your situation.
> >>
> >> Nyall
> >>
> >> >
> >> > regards
> >> > Stefan
> >> >
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> >
> >
>
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