[Gdal-dev] ADO driver based on OpenGIS SQL specification in OGR
warmerdam at pobox.com
Thu Jul 24 20:16:37 EDT 2003
> The document « OpenGIS Simple features specification for SQL rev1.1 »
> describes the SQL92 implementation of features tables (www.opengis.org).
> As the Microsoft jet database engine is free on the Windows' system,
> this could be a good way to have a Read/Write driver with a "performant"
> SQL engine.
> Indeed, I believe that these specifications are enough to create an
> Read/Write OGR driver with Geometries stored in wkb format. Am i wrong ?
> and is it interessting in OGR ?
Sorry for not replying sooner. I have been working hard on a couple projects
trying to get them out of the way before I take a week off next week.
Implementing OGC Simple Features for SQL (including the functions and datatypes)
is a pretty big job even with an existing full function SQL implementation
to build on. The Refractions guys did it for Postgres, but they had access
to the full source so they could update the database core. That would really
be practical (as far as I know) with the jet engine.
We could implement support storing geometry in WKB in using Jet, and have
OGR understand this, but with the database just treating the geometry as
a generic binary field. This would be somewhat useful, but not something
I am all the keen on spending alot of time on. Doing this in a way that it
would work with any ODBC supported database might be worthwhile, and a bit
more general. I would like to see this happen, but I don't know what all
the gotchas are. It is also not something I have funded or large amounts of
free time to work on. If it were to happen, it might well be done in such
a way as to be compatible with ESRI (or MapInfos?) use of access databasees
as lightweight spatial databases.
What we do have now is a solid PostGIS driver in OGR, and PostGIS implements
good and improving OGC compliance on a full featured database engine *with*
good spatial search performance. PostGIS/Postgres works quite well on
Windows (as well as unix of course), and is free. So I don't see a compelling
reason to search for another solution.
Now, I may have missed part of your point. Is there some advantage to using
ADO? Is the intent to implement on a database that is easily accessable from
VB? Do you think the Jet database is more performant than Postgres? It is,
no doubt, faster than the builtin OGR SQL implementation.
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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