Odp: SRID lost in ST_UNION

[Łukasz Szałek]

The same situation is in Postgis 3.5.0
@Erik Wienhold – do you know when some fix might appear?


Best regards
Łukasz Szałek


Od: Erik Wienhold <ewie at ewie.name>
Data: wtorek, 15 października 2024 o 15:59
Do: Łukasz Szałek <Lukasz.Szalek at tomtom.com>
DW: postgis-users at lists.osgeo.org <postgis-users at lists.osgeo.org>
Temat: Re: SRID lost in ST_UNION
[Nie otrzymujesz często wiadomości e-mail z ewie at ewie.name. Dowiedz się, dlaczego jest to ważne, na stronie https://aka.ms/LearnAboutSenderIdentification ]

On 2024-10-15 12:14 +0200, Łukasz Szałek via postgis-users wrote:
> 1)
> PostgreSQL 15.1 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
> POSTGIS="3.3.2 4975da8" [EXTENSION] PGSQL="150" GEOS="3.11.1-CAPI-1.17.1" PROJ="7.2.1" LIBXML="2.9.1" LIBJSON="0.11"
>
> Query:
> select ST_SRID(ST_GeomFromText('POLYGON ((4.9882543 50.4415584, 4.9882543 50.4415586, 4.9882545 50.4415586, 4.9882545 50.4415584, 4.9882543 50.4415584))',4326)), st_srid(ST_UNION(ARRAY[ST_GeomFromText('POLYGON ((4.9882543 50.4415584, 4.9882543 50.4415586, 4.9882545 50.4415586, 4.9882545 50.4415584, 4.9882543 50.4415584))',4326)]));
> st_srid | st_srid
> ---------+---------
>     4326 |    4326
> (1 row)
>
>
> 2)
> PostgreSQL 17.0 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 11.4.1 20231218 (Red Hat 11.4.1-3), 64-bit
> POSTGIS="3.3.7 a0c7967" [EXTENSION] PGSQL="170" GEOS="3.13.0-CAPI-1.19.0" PROJ="9.5.0" LIBXML="2.9.13" LIBJSON="0.14" LIBPROTOBUF="1.3.3" WAGYU="0.5.0 (Internal)"
>
> Query:
> select ST_SRID(ST_GeomFromText('POLYGON ((4.9882543 50.4415584, 4.9882543 50.4415586, 4.9882545 50.4415586, 4.9882545 50.4415584, 4.9882543 50.4415584))',4326)), st_srid(ST_UNION(ARRAY[ST_GeomFromText('POLYGON ((4.9882543 50.4415584, 4.9882543 50.4415586, 4.9882545 50.4415586, 4.9882545 50.4415584, 4.9882543 50.4415584))',4326)]));
> st_srid | st_srid
> ---------+---------
>     4326 |       0
>
> Is there a regression between those versions?

Yes, I see the same regression in 3.4.3 as well.  This is caused by [1]
which sets SRID=0 [2] because the SRID has not been determined at this
point.

[1] https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftrac.osgeo.org%2Fpostgis%2Fticket%2F5677&data=05%7C02%7CLukasz.Szalek%40tomtom.com%7Ca695afcc41294588cada08dced218a42%7C374f80267b544a3ab87d328fa26ec10d%7C0%7C0%7C638645975535855008%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=oRHG9AeOjggODtwV8AZwG5%2Boq6Wl9%2BcFs%2Fof2jZaMHE%3D&reserved=0<https://trac.osgeo.org/postgis/ticket/5677>
[2] https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftrac.osgeo.org%2Fpostgis%2Fbrowser%2Fgit%2Fpostgis%2Flwgeom_geos.c%3Frev%3Df37390b9cc4b33e8a7ec15e0396112fca19391c9%23L659&data=05%7C02%7CLukasz.Szalek%40tomtom.com%7Ca695afcc41294588cada08dced218a42%7C374f80267b544a3ab87d328fa26ec10d%7C0%7C0%7C638645975535881735%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=SFlNOLYkqr%2FTQNjEzAvH8%2FQHgI7OT2XSqE3e1rcve%2BE%3D&reserved=0<https://trac.osgeo.org/postgis/browser/git/postgis/lwgeom_geos.c?rev=f37390b9cc4b33e8a7ec15e0396112fca19391c9#L659>

--
Erik
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