[Qgis-user] Cross layer filtering

[Bernd Vogelgesang]

Hi,

idea #1: Do not create a virtual layer (tried this way for years and its 
still somehow a nightmare), but just duplicate you layer and switch it 
to rule based rendering with a CASE WHEN clause for the selected property.

idea #2: I do not know what you exactly mean with "bring in an 
associated layer" and how much of it you have to bring in, but maybe 
aggregate functions in other virtual fields will do the job?

I just recently dived into the aggregate stuff, and there are not too 
many good examples around. I find it pretty stable and did not encounter 
any crashes like with virtual layers (it just works or not). Might take 
a while for calculations (but that is just a question of hardware 
upgrades ;) )
When this is just for layout purposes in the composer, rendering time 
should not be as significant as well.

#3: Use themes!

When running into troubles, just ping me.

Cheers,
Bernd

p.s. maybe just bad ideas, but this just popped into my mind after my 
third beer

Am 28.03.24 um 14:39 schrieb Paul Wittle via QGIS-User:
> Hi,
> 
> I’ve been filtering a layer by adding a virtual column populated with 
> is_selected() and then creating a virtual layer from it using the filter:
> 
> WHERE virtualField = 1
> 
> This is working well and allows you to have a copy of the layer that 
> only shows the selected records when you are creating a layout.
> 
> I now need to bring in an associated layer, but I can’t find a reliable 
> way to cross layer filter because QGIS just hangs for ages and crashes.
> 
> I’ve searched around and can see a lot of people talk about making the 
> database do the work but of course it can’t if you are trying to use a 
> selection filter.
> 
> What is the most reliable way of setting up a filter based on a join 
> because QGIS tells me that I must use a virtual layer and even creates 
> it for me; but then it just hangs and crashes.
> 
> Is there a better way?
> 
> Info required to replicate:
> 
>   * Create a layer (mine is from Oracle DB) and add a virtual field
>     called “SelectedRow” with the formula “to_int(is_selected())”
>   * Bring in a second layer that has a one-to-many relationship based on
>     an attribute
>   * I’m trying to filter the second layer based on the first one where
>     the second layer must only include rows that match a selected key. 
> 
> Thank in advance for any tips,
> 
> Paul
> 
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-- 
Dipl.-Geogr.
Bernd Vogelgesang
Kappel 17
91355 Hiltpoltstein
Tel: 09192-3499427
mobil: 0163-1860160
mail at berndvogelgesang.de
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