Thank you Martin. With ST_ReducePrecision I got the expected result. The polygon, although is a complex one, is valid. I will file a ticket with a sample for the ST_Union issue. ________________________________ De: postgis-users <postgis-users-boun...@lists.osgeo.org> en nombre de Martin Davis <mtncl...@gmail.com> Enviado: martes, 6 de abril de 2021 20:46 Para: PostGIS Users Discussion <postgis-users@lists.osgeo.org> Asunto: Re: [postgis-users] Reduce precision using ST_union with gridSize
The issue with ST_Union not working with an empty polygon certainly sounds like a bug, and we should look into that. If you can file a ticket that would be great. (It would be helpful to have the polygon data which is causing the problem. Is it valid?) In any case now there is the function ST_ReducePrecision [1] which is specifically designed to do what you want. (It uses most of the same machinery as ST_Union, but should avoid whatever the issue with ST_Union is). [1] https://postgis.net/docs/manual-3.1/ST_ReducePrecision.html On Tue, Apr 6, 2021 at 7:28 AM Palacios García Cuevas, Elena <epgcue...@indra.es<mailto:epgcue...@indra.es>> wrote: Hello, I am trying to simplify a polygon by reducing the precision using ST_Union with the gridSize parameter ( I am using postgis 3.1 and GEOS 3.9.1). I have read that it is possible to do that by a union of a geometry with an empty geometry (http://blog.cleverelephant.ca/2020/12/waiting-postgis-31-3.html). However, does not works for me ( maybe is my fault because I am new with postgis). I have tried as follows: CREATE TABLE public.error_union_empty ( geom geometry(MultiPolygon), gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass), CONSTRAINT error_union_empty_pkey PRIMARY KEY (gid) ); INSERT INTO error_union_empty (SELECT ST_union(geom,ST_GeomFromText('POLYGON EMPTY'), 0.001152) geom FROM f_polygon); But the result is an empty table. Then I tried to do the same but by doing the union with the polygon himself, and this approach seems to work ok. CREATE TABLE public.error_union_empty2 ( geom geometry(MultiPolygon), gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass), CONSTRAINT error_union_empty2_pkey PRIMARY KEY (gid) ); insert into error_union_empty2 select ST_CollectionExtract(ST_union(f_polygon.geom,f_polygon.geom, 0.001152)) geom from f_polygon; Why is not working the first approach? Have I missed something in the query? Any help or comments are welcome. Does anyone knows if is expected to have a simplify with gridsize in the future? Thanks! ________________________________ Este correo electrónico y, en su caso, cualquier fichero anexo al mismo, contiene información de carácter confidencial exclusivamente dirigida a su destinatario o destinatarios. Si no es vd. el destinatario indicado, queda notificado que la lectura, utilización, divulgación y/o copia sin autorización está prohibida en virtud de la legislación vigente. En el caso de haber recibido este correo electrónico por error, se ruega notificar inmediatamente esta circunstancia mediante reenvío a la dirección electrónica del remitente. Evite imprimir este mensaje si no es estrictamente necesario. This email and any file attached to it (when applicable) contain(s) confidential information that is exclusively addressed to its recipient(s). If you are not the indicated recipient, you are informed that reading, using, disseminating and/or copying it without authorisation is forbidden in accordance with the legislation in effect. If you have received this email by mistake, please immediately notify the sender of the situation by resending it to their email address. Avoid printing this message if it is not absolutely necessary. _______________________________________________ postgis-users mailing list postgis-users@lists.osgeo.org<mailto:postgis-users@lists.osgeo.org> https://lists.osgeo.org/mailman/listinfo/postgis-users ________________________________ Este correo electrónico y, en su caso, cualquier fichero anexo al mismo, contiene información de carácter confidencial exclusivamente dirigida a su destinatario o destinatarios. Si no es vd. el destinatario indicado, queda notificado que la lectura, utilización, divulgación y/o copia sin autorización está prohibida en virtud de la legislación vigente. En el caso de haber recibido este correo electrónico por error, se ruega notificar inmediatamente esta circunstancia mediante reenvío a la dirección electrónica del remitente. Evite imprimir este mensaje si no es estrictamente necesario. This email and any file attached to it (when applicable) contain(s) confidential information that is exclusively addressed to its recipient(s). If you are not the indicated recipient, you are informed that reading, using, disseminating and/or copying it without authorisation is forbidden in accordance with the legislation in effect. If you have received this email by mistake, please immediately notify the sender of the situation by resending it to their email address. Avoid printing this message if it is not absolutely necessary.
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