[mapguide-users] Some thought on FDO PostGIS Provider

Thu Feb 18 03:11:50 EST 2010

this relates to http://trac.osgeo.org/fdo/wiki/FDORfc43

been a lot of discussions bout this over on FDO in the past

On Thu, Feb 18, 2010 at 7:08 PM, Kenneth Skovhede, GEOGRAF A/S
<ks at geograf.dk> wrote:
> Traian:
> Are you sure that the OGRProvider in MGOS 2.1 is dynamically loading gdal?
> My stock install has a 2mb+ OGRProvider.dll and has many strings inside from
> the OGR library.
> Also, when running MapGuide and viewing OGR data, I'm able to delete the
> gdal16.dll.
>
> OP:
> I have little real-world experience with the PostGIS provider, so I can
> only answer the Maestro related part of your question.
>
> The word "DataStore" is what the provider exposes the parameter as.
> Probably because it is based on the common RDBMS code.
> I can change the word in the userinterface for Maestro to "Schema",
> but it makes it slightly harder to guess how the value is mapped.
>
> I can also change it so Maestro suggests "public" as the schema when
> creating a new
> PostGIS FeatureSource.
>
> I have recorded the requests as issue #1275:
> http://trac.osgeo.org/mapguide/ticket/1275
>
> The naming issue sounds a little weird, it is supposed to be "Schema:Table",
> not "PostGIS:*" or "OGRSchema:*". The value listed in Maestro, is whatever
> the provider chooses to report. If you use the intended form (Schema:Table),
> you can see
> why Maestro cannot drop the Schema part, even if some propviders support
> using
> a default schema.
>
> Feel free to add an enhancement request for Maestro, for not including the
> schema part
> of the tablename for providers that misuse the naming scheme (and support a
> missing schema).
>
> The "update layers, when featuresource changes" request, is recorded as
> issue #1067
> http://trac.osgeo.org/mapguide/ticket/1067
>
> If there is any way you can provide reproduce able instructions for the save
> problem,
> please let me know.
>
> ***Non Maestro related follows ***
>
> Each time you start a map or something similar, MapGuide
> issues a DescribeSchema request. If you simply reference
> your entire database, this will take much longer than if you
> split it up in "schema" parts. I assume this is why the PostGIS provider
> does it this way. Obviously, the provider (or MapGuide) should be
> smart enough not to request all this info, but it is not.
>
> Also, if you expose your entire db, be aware that you are effectively
> exposing the database to the users. A rouge user can easily
> get MapGuide to hand over all exposed data, so the less there
> is avalible to MapGuide, the better.
>
> I have also built the OGR and Gdal provider with PostGIS support
> some time ago. I belive the build procedure is now so simple that
> it is just a matter of installing Visual Studio, checking out the code with
> SubVersion, and running the "build.bat".
>
> You only have to fiddle with the Gdal file called nmake.opts to have it
> include
> PostGIS.
>
> I would expect it to take a day or two to get a working build, if you want
> to try.
>
> Regards, Kenneth Skovhede, GEOGRAF A/S
>
> On 18-02-2010 06:20, Jason Birch wrote:
>>
>> To the OP:
>>
>> I understand your frusteration with getting PostGIS to work, but the
>> fact is that it's languishing because it hasn't had enough community
>> interest and development support. My organisation and Refractions
>> Research funded initial development of the provider by Mateusz, but it
>> never performed well enough to meet our needs. Following that, Geomap
>> GIS performed some bug fixes and maintenance. Apart from that there
>> has been very limited interest, funding, or development on this
>> provider. It looks like there may be some light at the end of the
>> tunnel now that Autodesk has resurrected and improved on a discarded
>> version of the initial provider, but you won't see benefit from that
>> until at least 2.2 if not later.
>>
>> To follow up on Traian's point, it's quite possible that the required
>> GDAL and plugins are available in the OSGeo4W repository. The mapguide
>> trac page for the GDAL provider (linked from the front page I think)
>> links to a message showing how to add raster plugins. After some
>> initial encouragement from Frank, all it took was a half hour or so
>> sitting with "depends.exe" to work out what I needed in addition to
>> gdal.dlls.  I'd imagine that vector/ogr plugins work the same way.
>>
>> Jason
>>
>> On 2010-02-17, Traian Stanev<traian.stanev at autodesk.com>  wrote:
>>
>>>>
>>>> Why OGR is no more built by default with PostGIS support?
>>>>
>>>
>>> It never was compiled with PostGIS by default. Before, I was doing a
>>> custom
>>> build with a static link to an OGR build which has PostGIS support built
>>> in.
>>> Needless to say that takes a long time to do due to the huge dependency
>>> list
>>> and there have only been one or two people who have asked for it, so not
>>> enough demand to make it worth my time.
>>>
>>> However, since the default build now uses dynamic link to the GDAL DLL,
>>> you
>>> should be able to replace the Gdal.dll with one that has PostGIS support
>>> compiled in it and automatically get PostGIS support.
>>>
>>>
>>>
>>>>
>>>> That said, if you know an URL with OGR dll compiled with PostGIS
>>>> support, in a version compatible with Mapguide, I would rather try
>>>> them, before starting editing the 1000 layers...
>>>>
>>>
>>> I only have such builds for FDO 3.3 (MG 1.2), posted at 13-9.com. If
>>> there
>>> is enough demand, I could try to do a build with whatever FDO the "new"
>>> MGOS
>>> is using -- but it would really be better if someone else who is more
>>> vested
>>> in this volunteered, and I could provide some support with how to build
>>> it.
>>>
>>>
>>> Traian
>>>
>>>
>>> -----Original Message-----
>>> From: mapguide-users-bounces at lists.osgeo.org
>>> [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Gabriele
>>> Monfardini
>>> Sent: Wednesday, February 17, 2010 6:48 AM
>>> To: MapGuide Users Mail List
>>> Subject: [mapguide-users] Some thought on FDO PostGIS Provider
>>>
>>> Hi all,
>>>
>>> I am trying Mapguide 2.1 and FDO PostGIS provider (using Maestro 2.0
>>> RC1).
>>>
>>> The provider uses the word "datastore" to refer to PostgreSQL schema
>>> (http://www.postgresql.org/docs/current/interactive/ddl-schemas.html).
>>> This is very misleading since there are schemas and tablespaces in
>>> PostgreSQL, but no datastores.
>>> Moreover (this can be a Maestro issue) the default value seems to be
>>> empty instead of "public", that is the default schema present in all
>>> PostgreSQL databases.
>>>
>>> Second problem: what is the reason to include the schema in the
>>> dataconnection?
>>> I mean, I want to connect to a specific database, not to a specific
>>> schema inside the database.
>>> The schema and the table should be part of layer definition, as in OGR
>>> Provider.
>>> This would be better from a logic point of view and I don't know of
>>> any application that requires to specify the schema before connecting
>>> to a PostgreSQL db.
>>>
>>> One may think this is a minor issue.
>>> In fact it depends on the size of the repository.
>>>
>>> I'm about to migrate from Mapguide 1.2 OGR Provider to 2.1 PostGIS
>>> Provider.
>>> I have around 40 databases, each one with 5-10 schemas for a total of
>>> over 1000 layers.
>>> With Postgis Provider I have to create 200-400 dataconnection (instead
>>> of 40) and manually modify all 1000 layers.
>>> The last part is needed since the layer specifies in the FeatureName
>>> the dataconnection provider type (that has to be updated from
>>> OGRSchema:schema~table to FdoPostGIS:table) and from my preliminary
>>> experiments Maestro is not so smart to update the layers when I change
>>> only the dataconnection type, but not its name.
>>>
>>> I do not consider this a Maestro issue (in fact its smartness is
>>> already invaluable), but a not so smart decision when designing the
>>> XML schema.
>>> Since the layer specifies the ResourceId, IMHO there is no apparent
>>> need to decorate its FeatureName with dataconnection provider type.
>>> But maybe I'm ignoring something.
>>>
>>> I've also probably found a bug in FDO PostGIS provider.
>>> If at least one table in the schema contains a field of type
>>> "timestamp with time zone", the provider is not able to describe the
>>> schema.
>>>
>>> Trying to save such a dataconnection into the repository (with
>>> Maestro) or trying to create a layer with this dataconnection leads to
>>> errors in Mapguide 2.1.
>>> Not always the errors are the same (different paths in the code
>>> depending to resource already cached or not?), and I report the three
>>> more commons:
>>>
>>> 1 -  "describe schema command failed" at
>>> mgdev\server\src\services\feature\ServerDescribeSchema.cpp, line 204
>>>
>>> <2010-02-15T18:06:59>   512     MapGuide Maestro
>>> v2.0.0.4569     10.1.1.244      Administrator
>>>  Error: An exception occurred in FDO component.
>>>         The describe schema command failed for 'FdoPostGIS' schema.
>>>  StackTrace:
>>>   - MgFeatureServiceHandler.ProcessOperation() line 83 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\FeatureServiceHandler.cpp
>>>   - MgOpDescribeSchemaAsXml.Execute() line 110 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\OpDescribeSchemaAsXml.cpp
>>>   - MgServerFeatureService.DescribeSchemaAsXml() line 333 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerFeatureService.cpp
>>>   - MgServerDescribeSchema.DescribeSchemaAsXml() line 628 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>   - MgServerDescribeSchema.DescribeSchema() line 564 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>   - MgServerDescribeSchema.DescribeFdoSchema() line 204 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>
>>>
>>> 2 - "Null reference" at
>>> \mgdev\server\src\services\feature\ServerDescribeSchema.cpp, line 77
>>> (not so auto-explaining message for the user)
>>>
>>> <2010-02-15T17:50:02>   2556    MapGuide Maestro
>>> v2.0.0.4569     10.1.1.244      Administrator
>>>  Error: Null reference.
>>>  StackTrace:
>>>   - MgFeatureServiceHandler.ProcessOperation() line 83 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\FeatureServiceHandler.cpp
>>>   - MgOpDescribeSchemaAsXml.Execute() line 110 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\OpDescribeSchemaAsXml.cpp
>>>   - MgServerFeatureService.DescribeSchemaAsXml() line 333 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerFeatureService.cpp
>>>   - MgServerDescribeSchema.DescribeSchemaAsXml() line 628 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>   - MgServerDescribeSchema.DescribeSchema() line 564 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>   - MgServerDescribeSchema.DescribeFdoSchema() line 77 file
>>>
>>> c:\osgeo\mapguide_21\mgdev\server\src\services\feature\ServerDescribeSchema.cpp
>>>
>>>
>>> 3 - A terrible MgInvalidStreamHeaderException that seems not properly
>>> catched and crashes the server, without logging anything at all.
>>> This seems to happen more often when trying to create the layer
>>> selecting the dataconnection.
>>> This one appears to be a bug in Mapguide.
>>>
>>> I've also find a possible bug in Maestro.
>>> When I try to save the problematic dataconnection it warns me that FDO
>>> connection failed and offers to save it anyway. Sometimes, even if I
>>> save it, it does not record correctly the Datastore, leaving it empty
>>> in the XML.
>>>
>>> Last "rant".
>>> Why OGR is no more built by default with PostGIS support?
>>> It would have provided me a much more smooth upgrade from 1.2.
>>> Moreover, FDO PostGIS Provider is quite recent, initially developed
>>> only for Windows, and I suspect not so much used.
>>> Having 2 possible connection to PostGIS would offer the possibilities
>>> to compare the performances (that in my situation are very important)
>>> and choose the best one.
>>>
>>> I am not so happy to drop here and there new dlls, also because in my
>>> experience MG is quite strict on library versions, and at least
>>> version 1.2 quite poor on logging useful information. So this could
>>> lead to not-logged crashes or generic errors that are very difficult
>>> to solve.
>>>
>>> That said, if you know an URL with OGR dll compiled with PostGIS
>>> support, in a version compatible with Mapguide, I would rather try
>>> them, before starting editing the 1000 layers...
>>>
>>> Regards,
>>>
>>> Gabriele Monfardini
>>> _______________________________________________
>>> mapguide-users mailing list
>>> mapguide-users at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/mapguide-users
>>>
>>>
>>
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>>
>
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-- 
Zac Spitzer
Solution Architect / Director
Ennoble Consultancy Australia
http://www.ennoble.com.au
http://zacster.blogspot.com
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