[mapserver-dev] PostGIS "curvepolygon" support

[Paul Ramsey]

On Tue, Nov 9, 2010 at 1:46 AM, Astrid Emde <astrid.emde at wheregroup.com> wrote:
> I would favorite the solution b) to make the functionality generally
> available.
>
> But just a question - we always will have the process of stroking PostGIS
> curves which will be a performance leak. Am I right?

Yes, but as Frank noted, not a particularly big performance leak.

> At the moment we preprocess our data and create the strokes in the database
> in a second geom_column. So we loose no performance as we access the
> preprocessed data in our mapfiles. Solution b) will still do the
> "stroke-processing" on-the-fly.
>
> Frank offered to implement a solution in GDAL/OGR so this would be for
> CONNECTIONTYPE OGR and the solution you suggested would be for
> CONNECTIONTYPE POSTGIS. Is this right?

Nope, we both suggested doing it in CONNECTIONTYPE POSTGIS, which is
the right place in this case, IMO.

Best,

Paul

> Paul Ramsey schrieb:
>>
>> Astrid,
>>
>> It would make sense to generally handle the curvey types in the run,
>> including the compoundcurve and circularstring as forms of mapserver
>> LINE types. I think your thread suggestion is correct (perhaps?) in
>> that it would be "simplest" to just paper over the curve types in the
>> postgis driver. This is in fact what is happening (sort of) in the
>> Oracle driver already.
>>
>> The papering-over could take two forms.
>>
>> (a) We could change the SQL being send to PostGIS to ensure that
>> curves are stroked (turned into equivalent linestrings) on the
>> database side.
>> (b) Or we could extract the stroking routines that have already been
>> written in the Oracle driver to a globally accessible area, genericize
>> them a little, and use them to stroke PostGIS curves in the MapServer
>> code.
>>
>> The advantage of (b) is that the stroking routines would then be
>> generically available to any other driver that needs to stroke curves.
>> It would be a little more work than hacking up the SQL generated by
>> the PostGIS driver to get the server to do the work of stroking.
>>
>> Does anyone else have interest in this issue?
>>
>> Paul
>>
>> On Mon, Nov 8, 2010 at 11:06 PM, Astrid Emde <astrid.emde at wheregroup.com>
>> wrote:
>>
>>>
>>> Hello devs,
>>>
>>> there was a discussion going on about PostGIS "curvepolygon" support for
>>> MapServer. At the moment polygons without curves are
>>> drawn, the ones with curves not.
>>>
>>> Here is the discussion link:
>>>
>>>
>>> http://osgeo-org.1803224.n2.nabble.com/PostGIS-curvepolygon-support-tt5372049.html
>>>
>>> One of our customers would like to sponsor this implementation and would
>>> like to know how much this enhancement would cost. It would be good if
>>> you
>>> could handle polygons and curevepolygons in one MapServer layer from TYPE
>>> POLYGON.
>>>
>>> In the thread there was also the discussion about a solution which is
>>> implemented in the PostGIS driver ...
>>>
>>>
>>>>
>>>>  Curiously could this mean adding to the PostGIS driver a means of
>>>>  going from curve to shapeObj? As opposed to adding a curve shape
>>>>  type within MapServer.
>>>>
>>>
>>> Could you please discuss a possible solution and estimate the costs? Who
>>> would be the contact person concerning this enhancement?
>>>
>>> Maybe there are other MapServer users interested in this enhancement and
>>> would also sponsor the implementation.
>>>
>>> --
>>>
>>> Best regards
>>> Astrid Emde
>>>
>>> ----------------------------------
>>>
>>> Aufwind durch Wissen!
>>>
>>> Qualifizierte OpenSource-Schulungen
>>> bei der www.foss-academy.eu
>>>
>>> ----------------------------------
>>>
>>> Astrid Emde
>>> WhereGroup GmbH & Co.KG
>>> Siemensstraße 8
>>> 53121 Bonn
>>> Germany
>>>
>>> Fon: +49(0)228 90 90 38 - 19
>>> Fax: +49(0)228 90 90 38 - 11
>>>
>>> astrid.emde at wheregroup.com
>>> www.wheregroup.com
>>>
>>> Amtsgericht Bonn, HRA 6788
>>> -------------------------------
>>> Komplementärin:
>>> WhereGroup Verwaltungs GmbH
>>> vertreten durch:
>>> Olaf Knopp, Peter Stamm
>>> -------------------------------
>>>
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>>>
>>>
>
>
> --
>
> Mit freundlichen Grüßen
>
> Astrid Emde
>
> ----------------------------------
>
> Aufwind durch Wissen!
>
> Qualifizierte OpenSource-Schulungen
> bei der www.foss-academy.eu
>
> ----------------------------------
>
> Astrid Emde
> WhereGroup GmbH & Co.KG
> Siemensstraße 8
> 53121 Bonn
> Germany
>
> Fon: +49(0)228 90 90 38 - 19
> Fax: +49(0)228 90 90 38 - 11
>
> astrid.emde at wheregroup.com
> www.wheregroup.com
>
> Amtsgericht Bonn, HRA 6788
> -------------------------------
> Komplementärin:
> WhereGroup Verwaltungs GmbH
> vertreten durch:
> Olaf Knopp, Peter Stamm
> -------------------------------
>
> _______________________________________________
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