[geos-devel] Is Overlay-NG active?

[Roger Bivand]

On Thu, 15 Oct 2020, Regina Obe wrote:

>>> Roger,
>>>
>>> I'll let Paul answer the question of when we can expect a 3.9 as he
>>> probably has a better idea than anyone else. All I know is the plan is
>>> we'll be releasing GEOS 3.9 and PostGIS 3.1 around the same time since
>>> there is some functionality in PostGIS 3.1 that leverages GEOS 3.9 if
>>> it is compiled with GEOS 3.9.
>>>
>>> As far as testing, on the PostGIS side to make the old Geos and new
>>> Geos agree, I've been applying ST_Normalize
>>>
>>> Which looks to come from Geos CAPI - GEOSNormalize
>>>
>>> Can you use that to deal with the failures you are running into?  That
>>> should make the wkt of both GEOS old and new agree.
>>
>> Thank you, yes, probably. However, both legacy overlay and Overlay-NG
>> differ from GEOSNormalize() (as far as I can see from a simple test), so
> the
>> half-dozen package maintainers will need to go from legacy to normalized
>> and then avoid having to condition on the GEOS version.
>>
>> Best wishes,
>>
>> Roger
>>
>
> Yah both legacy and NG both defer from GEOSNormalize, but the GEOSNormalize
> of both is equivalent so what we do is
>
> Essentially
>
> WKT(GeosNormalize(outputfromfunc)) = WKT(GeosNormalize(oldexpectedresult))
>
> Not ideal I know and maybe much harder to do in your setup than it was on
> our tests as it does require changing your wkt expected output to the
> normalized version.

Regina,

Thanks again. Since we accept that we can rely on the existing WKT 
representations remaining fixed < "3.9.0", and that Overlay-NG will be 
used >= "3.9.0", we are choosing to advise package maintainers to add a 
condition to their tests to add the new >= "3.9.0" WKT when GEOS >= 
"3.9.0". Not ideal, but we can return to normalization later if this isn't 
enough.

Best wishes,

Roger

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-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en