[geos-devel] geos-devel Digest, Vol 238, Issue 6, && operator

[Lars Aksel Opsahl]

>Message: 1
>Date: Thu, 8 Sep 2022 00:08:23 +0200
>From: Sandro Santilli <strk at kbt.io>
>To: GEOS Development List <geos-devel at lists.osgeo.org>
>Subject: Re: [geos-devel] GEOS C API for Polygonal Coverage
>        operations?
>Message-ID: <YxkWV0gym7hqAesi at c19>
>Content-Type: text/plain; charset=us-ascii
>
>On Tue, Sep 06, 2022 at 02:37:37PM -0700, Martin Davis wrote:
>> I've started to build out operations on Polygonal Coverages in JTS ([1],
>> [2]).
>
>[...]
>
>> A key question is how to expose these operations in the GEOS C API.  I see
>> two options:
>> 1) Model a Polygonal Coverage as an array of simple Polygons (and possibly
>> MultiPolygons)
>> 2) Provide a Polygonal Coverage datatype (which might contain internal
>> topology)
>
>Could a coverage datatype allow performing operations on PostGIS Topologies
>w/out building the polygons for each face ? There's an ISO standard
>representation of topologies, maybe such representation could be used
>to transfer those topologies back and forth with GEOS ?
>
>--strk;
>
>
>------------------------------
>

Hi

To speed up now I sometimes use the faces directly like below so yes it would be very nice to avoid code like this:

SELECT distinct t.omrade, ((t.omrade).id)
FROM topo_rein.arstidsbeite_var_flate t, topology tt, topology.layer tl, topo_rein_sysdata_rvr.relation tr, topo_rein_sysdata_rvr.face tf
WHERE
((t.omrade).topology_id = tt.id AND (t.omrade).layer_id = tl.layer_id AND (t.omrade).type = tl.feature_type) AND
tr.topogeo_id = ((t.omrade).id) AND
((t.omrade).layer_id) = tr.layer_id AND ((t.omrade).id) = tr.topogeo_id AND tf.face_id = tr.element_id AND ((t.omrade).type) = tr.element_type AND
tf.mbr &&
'0103000020A21000000100000005000000EF94C2D58F783C4082E16983FE605140EF94C2D58F783C40AA4578DB36945140A4B7A470A6453D40AA4578DB36945140A4B7A470A6453D4082E16983FE605140EF94C2D58F783C4082E16983FE605140'
AND
ST_Intersects('0103000020A21000000100000005000000EF94C2D58F783C4082E16983FE605140EF94C2D58F783C40AA4578DB36945140A4B7A470A6453D40AA4578DB36945140A4B7A470A6453D4082E16983FE605140EF94C2D58F783C4082E16983FE605140', t.omrade)

So could it also be an option to let && operator to know about about Topology type is extension added as a start and then the && operator could include code like this ?

'((t.omrade).topology_id = tt.id AND (t.omrade).layer_id = tl.layer_id AND (t.omrade).type = tl.feature_type) AND
tr.topogeo_id = ((t.omrade).id) AND
((t.omrade).layer_id) = tr.layer_id AND ((t.omrade).id) = tr.topogeo_id AND tf.face_id = tr.element_id AND ((t.omrade).type) = tr.element_type AND'

The best off course is if this was solved in geos as you suggest, but it would help a lot if the code below used the face.mbr indexes also as a start.

SELECT distinct t.omrade, ((t.omrade).id)
FROM topo_rein.arstidsbeite_var_flate t
WHERE
t.omrade &&
'0103000020A21000000100000005000000EF94C2D58F783C4082E16983FE605140EF94C2D58F783C40AA4578DB36945140A4B7A470A6453D40AA4578DB36945140A4B7A470A6453D4082E16983FE605140EF94C2D58F783C4082E16983FE605140'
AND
ST_Intersects('0103000020A21000000100000005000000EF94C2D58F783C4082E16983FE605140EF94C2D58F783C40AA4578DB36945140A4B7A470A6453D40AA4578DB36945140A4B7A470A6453D4082E16983FE605140EF94C2D58F783C4082E16983FE605140', t.omrade)

Lars
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