From senhor.neto at gmail.com  Mon Apr 13 10:15:21 2026
From: senhor.neto at gmail.com (Alexandre Neto)
Date: Mon, 13 Apr 2026 18:15:21 +0100
Subject: ST_SNAP behaviour with 3D Geometries
Message-ID: <CA+H0G_EQ9E08E2fdEX9-dbid0DRxvLtnQNu2gT8uJ3N3YFxVcQ@mail.gmail.com>

Hi all,

I am having trouble understanding the behaviour of St_Snap when used with
3D Geometries.

I was aware that st_snap did not properly support 3D geometries, but I
would not expect that it actually changes the Z coordinates.

I would expect that the Z coordinates would be kept untouched, but that's
not what happens.

WITH input AS (SELECT 'POINT Z (1.001 1.001 50)'::geometry AS geom),

reference AS (SELECT 'POINT Z (1.0 1.0 999)'::geometry AS geom)

SELECT

ST_AsEWKT(ST_Snap(i.geom, r.geom, 0.01)) AS snapped,

ST_Z(ST_Snap(i.geom, r.geom, 0.01)) AS z_after_snap,

ST_Z(i.geom) AS z_original

FROM input i, reference r;




*snapped
|z_after_snap|z_original|--------------+------------+----------+POINT(1 1
999)|       999.0|      50.0|*

In fact, not only the Z coordinate gets changed as it completely ignores
the tolerance.

I then tried to use ST_Force2D around the reference geometry, but the
result is kind of expected, a 2D geometry with no Z coordinate.

I wonder if these are the expected behaviour of ST_snap and there is more a
convenient way to snap 3D geometries in 2D while ignoring the Z component
without needing to recover all vertices Zs from the original geometry.

Thanks,

Alexandre Neto
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From pramsey at cleverelephant.ca  Tue Apr 14 16:47:55 2026
From: pramsey at cleverelephant.ca (Paul Ramsey)
Date: Tue, 14 Apr 2026 16:47:55 -0700
Subject: Patch Releases 3.6.3, 3.5.6, 3.4.6, 3.3.10, 3.2.10
Message-ID: <E030D984-5EEC-4AB1-A6CD-415E659F8FDC@cleverelephant.ca>

The PostGIS development team is pleased to provide bug fix and security releases <https://postgis.net/source> for PostGIS 3.2 - 3.6.

3.6.3 source <https://download.osgeo.org/postgis/source/postgis-3.6.3.tar.gz> md5 <https://postgis.net/stuff/postgis-3.6.3.tar.gz.md5> NEWS <https://git.osgeo.org/postgis/postgis/raw/tag/3.6.3/NEWS> docs: en <https://download.osgeo.org/postgis/docs/postgis-3.6.3-en.pdf>
3.5.6 source <https://download.osgeo.org/postgis/source/postgis-3.5.6.tar.gz> md5 <https://postgis.net/stuff/postgis-3.5.6.tar.gz.md5> NEWS <https://git.osgeo.org/postgis/postgis/raw/tag/3.5.6/NEWS> docs: en <https://download.osgeo.org/postgis/docs/postgis-3.5.6-en.pdf>
3.4.6 source <https://download.osgeo.org/postgis/source/postgis-3.4.6.tar.gz> md5 <https://postgis.net/stuff/postgis-3.4.6.tar.gz.md5>  NEWS <https://git.osgeo.org/postgis/postgis/raw/tag/3.4.6/NEWS> docs: en <https://download.osgeo.org/postgis/docs/postgis-3.4.6-en.pdf>
3.3.10 source <https://download.osgeo.org/postgis/source/postgis-3.3.10.tar.gz> md5 <https://postgis.net/stuff/postgis-3.3.10.tar.gz.md5> NEWS <https://git.osgeo.org/postgis/postgis/raw/tag/3.3.10/NEWS> docs: en <https://download.osgeo.org/postgis/docs/postgis-3.3.10.pdf>
3.2.10 source <https://download.osgeo.org/postgis/source/postgis-3.2.10.tar.gz> md5 <https://postgis.net/stuff/postgis-3.2.10.tar.gz.md5>  NEWS <https://git.osgeo.org/postgis/postgis/raw/tag/3.2.10/NEWS> docs: en <https://download.osgeo.org/postgis/docs/postgis-3.2.10.pdf>
Please refer to the links above for more information about the issues resolved by these releases.
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