different results for ST_Relate with 3 parameters compared to those for ST_Relate with 2 parameters

[Antonio Valanzano]

Here is the details of my installation:

"postgis_full_version"
"POSTGIS=""3.5.2 3.5.2"" [EXTENSION] PGSQL=""170""
GEOS=""3.13.0-CAPI-1.19.0"" PROJ=""8.2.1 NETWORK_ENABLED=OFF URL_ENDPOINT=
https://cdn.proj.org
USER_WRITABLE_DIRECTORY=C:\Windows\ServiceProfiles\NetworkService\AppData\Local/proj
DATABASE_PATH=C:\Program
Files\PostgreSQL\17\share\contrib\postgis-3.5\proj\proj.db"" (compiled
against PROJ 8.2.1) LIBXML=""2.12.5"" LIBJSON=""0.12""
LIBPROTOBUF=""1.2.1"" WAGYU=""0.5.0 (Internal)"""

Antonio



Il giorno mer 15 ott 2025 alle ore 19:28 Paul Ramsey <
pramsey at cleverelephant.ca> ha scritto:

> Maybe you have found an old bug? Running exactly the same SQL as you, I
> get two rows from each query.
>
> postgis=# SELECT
>
>             d.id,
>
>                        ST_Relate(d.geom, l.geom) as patternMatrix
>
>                               FROM docks as d, lakes as l
>
>                                        WHERE ST_Relate(d.geom, l.geom,
> '1FF00F212');
>  id | patternmatrix
> ----+---------------
>   1 | 1FF00F212
>   2 | 1FF00F212
> (2 rows)
>
> postgis=# SELECT
> postgis-#   d.id,
> postgis-#   ST_Relate(d.geom, l.geom) as patternMatrix
> postgis-# FROM docks as d, lakes as l
> postgis-# WHERE ST_Relate(d.geom, l.geom) = '1FF00F212';
>  id | patternmatrix
> ----+---------------
>   1 | 1FF00F212
>   2 | 1FF00F212
> (2 rows)
>
> postgis=#
> postgis=# select postgis_full_version();
>
>
>
> postgis_full_version
>
>
>
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>  POSTGIS="3.7.0dev 3.6.0rc2-134-g5dc95f1bc" [EXTENSION] PGSQL="180"
> GEOS="3.15.0dev-CAPI-1.21.0" PROJ="9.6.2 NETWORK_ENABLED=ON URL_ENDPOINT=
> https://cdn.proj.org
> USER_WRITABLE_DIRECTORY=/Users/pramsey/Library/Application Support/proj
> DATABASE_PATH=/opt/homebrew/Cellar/proj/9.6.2/share/proj/proj.db" (compiled
> against PROJ 9.6.2) LIBXML="2.9.13" LIBJSON="0.18" LIBPROTOBUF="1.5.2"
> WAGYU="0.5.0 (Internal)" (core procs from "3.7.0dev
> 3.6.0rc2-125-g747d7732b" need upgrade)
>
> On Wed, Oct 15, 2025 at 9:22 AM Antonio Valanzano <anvalanz at gmail.com>
> wrote:
>
>> I am following the "Introduction to PostGIS " tutorial  at
>> https://postgis.net/workshops/postgis-intro/
>> and for chapter 26 "Dimensionally Extended 9-Intersection Model"  I am
>> trying to replicate the examples.
>>
>> If I use the two different versions of ST_Relate I do not obtain the same
>> result
>>
>> SELECT
>>   d.id,
>>   ST_Relate(d.geom, l.geom) as patternMatrix
>> FROM docks as d, lakes as l
>> WHERE ST_Relate(d.geom, l.geom, '1FF00F212') = true;
>> -- 1 row
>> "id" "patternmatrix"
>> 1    "1FF00F212"
>>
>>
>>
>> SELECT
>>   d.id,
>>   ST_Relate(d.geom, l.geom) as patternMatrix
>> FROM docks as d, lakes as l
>> WHERE ST_Relate(d.geom, l.geom) = '1FF00F212';
>> -- 2 rows
>> "id" "patternmatrix"
>> 1    "1FF00F212"
>> 2    "1FF00F212"
>>
>> Could someone give me an explanation of such a difference ?
>>
>>
>>
>>
>>
>
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