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I agree with Nathan, for algorithms, symbology and a lot of small
things it will become very complicated.<br>
<br>
As an alternative approach, we could think about having some layer
settings defined on group level (and maybe even a merged attribute
table for the whole group). That would already make a lot of things
easier to configure for multiple layers at once. We could even mark
such a group as a "union layer group" or similar, so for algorithms
that support this kind of thing it would be possible to offer such a
"union layer group" as choice while all other things just continue
to work.<br>
<br>
Matthias<br>
<br>
<div class="moz-cite-prefix">On 04/02/2015 02:30 PM, Nathan Woodrow
wrote:<br>
</div>
<blockquote
cite="mid:CAAi8Yg_2wrxaUo650U4Pvg9KceYw=4EQ9d6XL=BT46mPG-YPsw@mail.gmail.com"
type="cite">
<p dir="ltr">I would not be in favour of supporting a many
geometry type per layer type setup, it just makes things a heap
more complicated IMO for little gain. </p>
<p dir="ltr">Also makes your code a lot more complicated, you now
have to check each geometry for type because you are never sure
what you will get.</p>
<p dir="ltr">MapInfo did this and it was more a pain then a
feature.</p>
<br>
<div class="gmail_quote">On Thu, 2 Apr 2015 10:11 pm Denis Rouzaud
<<a moz-do-not-send="true"
href="mailto:denis.rouzaud@gmail.com">denis.rouzaud@gmail.com</a>>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Hi Olivier,<br>
<br>
I think you can easily extend your reasoning to the support
of multiple geometry columns in QGIS.<br>
I believe that this would come in QGIS at some point.<br>
<br>
If QGIS 3 is getting closer, our company will support this
feature. <br>
<br>
As you suggest, the layer could have different geometry
types and/or columns. This could be seen as sub-layer level
for rendering:<br>
layer > geometry types/columns > symbology rules<br>
<br>
I suppose this is quite a big change. Many things depends on
the geometry type in QGIS (like map map tools), and that
would represent a large API break.<br>
<br>
But, on my side, I believe it's a logic evolution for QGIS.<br>
<br>
Best wishes,<br>
<br>
Denis</div>
<div bgcolor="#FFFFFF" text="#000000"><br>
<br>
<br>
<br>
<br>
<br>
<div>On 04/02/2015 01:52 PM, Olivier Dalang wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hi,</div>
<div><br>
</div>
<div>In some projects of mine, I work with multiple
geometry types in one postgis table, using a column of
type <font style="background-color:rgb(238,238,238)"
face="monospace, monospace">geometry(Geometry,4326)</font>.</div>
<div>This is very well supported by postgis.</div>
<div><br>
</div>
<div>It is possible to load such a table in QGIS by
manually selecting the geometry type you want to load.
This means that to display all the features, you need
to add the table three times, one for each feature
type.</div>
<div><br>
</div>
<div>This works more or less. There are a few bugs
though :</div>
<div>- <a moz-do-not-send="true"
href="http://hub.qgis.org/issues/12499"
target="_blank">http://hub.qgis.org/issues/12499</a>
(you can edit other type's node with the node tool)</div>
<div>- <a moz-do-not-send="true"
href="http://hub.qgis.org/issues/12500"
target="_blank">http://hub.qgis.org/issues/12500</a>
(other type's records are shown in the attribute
table)</div>
<div><br>
</div>
<div>This also has some limitations. When having such a
setup, it's pretty sure you'll want to have the same
edit forms for all the layers. You'll also probably
want the same filter, the same labels, the same
actions, etc...</div>
<div>The only thing you'd want to be able to define on a
geometry type basis are the symbol (well, even the
classification/colors/etc could be shared) and the
label placement.</div>
<div>For now, you must do all settings three times,
because of this bug/feature request :</div>
<div>- <a moz-do-not-send="true"
href="http://hub.qgis.org/issues/12303"
target="_blank">http://hub.qgis.org/issues/12303</a>
(copy/paste style from one geometry type to another)</div>
<div><br>
</div>
<div><br>
</div>
<div>As you see, support multiple geometry types in QGIS
is not perfect.</div>
<div><br>
</div>
<div>Of course it's possible to fix the bugs/pr, and
there are some workarounds (postgis view instead of
tables) but maybe it's also worth thinking a bit more
in depth about this.</div>
<div><br>
</div>
<div>We could consider point/line/polygons as
subcategories/sublayers of a layer. A shapefile or a
mono-typed table would have only one of those
sublayer, but a postgis table could perfectly have the
three. Most of the settings would be defined at the
layer level, while only some settings would be defined
at the subcategory level.</div>
<div><br>
</div>
<div>This is probably especially relevant when thinking
long term (the day we support 3D, curves, etc...).</div>
<div><br>
</div>
<div><br>
</div>
<div>What do you think ?</div>
<div>Do you think the relation 1 layer = 1 geometry type
will hold ?</div>
<div><br>
</div>
<div>I think we inherited this from the old shapefile
format, but most data sources QGIS handles don't have
this limitation. I also think it does not hold with
quite a lot of modern GIS uses (especially web
related, think of openstreetmaps for instance).</div>
<div><br>
</div>
<div>There's this feature request (6th oldest open issue
on the tracker) about postgis geometry collections :
<a moz-do-not-send="true"
href="http://hub.qgis.org/issues/167"
target="_blank">http://hub.qgis.org/issues/167</a></div>
<div><br>
</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Olivier</div>
<div><br>
</div>
</div>
<br>
<br>
<br>
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