[mapserver-dev] GSoC Ideas for MapServer

[Even Rouault]

Le vendredi 20 février 2015 23:24:40, Daniel Morissette a écrit :
> On 2015-02-20 4:21 PM, Oliver Courtin wrote:
> > Le 19 févr. 2015 à 15:35, Even Rouault a écrit :
> > 
> > Hi Even,
> > 
> >> I doubt the overhead introduced by OGR would be really significant if
> >> you take into account the whole chain
> > 
> > I you have doubts, i have not :)
> > And this not because of OGR itself, but because of an abstraction layer
> > in the middle. It would cost (mostly on big GetFeature requests).
> 
> My 0.02$:
> 
> While I can appreciate Olivier's design goals, I can also see the HUGE
> value provided by OGR support in TinyOWS for lots of users, and doing it
> with the help of libs such as GEOS is clearly feasible even if it might
> result in a bridge of (slightly) inferior quality to the support
> provided by the prime backends (PostGIS, Oracle SPatial and SQLite).
> 
> The challenge may be a bit big for a GSoC student, but I think we
> shouldn't completely rule out the idea of supporting OGR in TinyOWS if
> the right project and funding became available.

I can understand Olivier's worries too, and there might be indeed technical 
difficulties due to the abstraction that would hide a few things that might be 
needed.

Regarding ST_GeomFromGML(), OGR has OGR_G_CreateGeometryFromGML(), which 
coupled with OGR_G_ExportToWKB()/OGR_G_ExportToWKT() should please most 
backends.

Anyway, if other backends are added to TinyOWS, I guess that the code 
refactoring that would result of that work would at least make it a possible 
option (like the virtual table mechanism used for the various backends in 
MapServer). I guess that the abstraction that could result could look like the 
OGR abstraction. For WFS-T, you need GetNextFeature() (SELECT), 
CreateFeature() (INSERT), SetFeature() (UPDATE), DeleteFeature() (DELETE), 
GetFeatureCount() (SELECT COUNT(*) FROM), StartTransaction() (BEGIN) ...

I'd be curious if someone has measured the overhead of OGR use in MapServer 
when doing native shapefile/postgis/OCI/mssqlspatial(/SDE !) vs OGR 
shapefile/postgis/OCI/mssqlspatial(/SDE), for example in WFS.

Even

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