SRID lost in ST_UNION

[Łukasz Szałek]

Hi all

Sorry for the email, I am new at this list. I hope this is a correct way to post issue.
Anyway what I have is:

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?
Thanks for any info and help

Best regards
Lukasz Szalek

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