[fdo-users] FDO Usage Questions

[Dan Stoica]

Regarding " The SpatialExtents function through SelectAggregates is very slow, almost as bad as simply reading the Geometries." please note ArcGis doesn't have a native method to accomplish this. Therefore the provider delegates the task to the Expression Engine which is computing the extents by brute force. 

In general, for FDO usage examples, I recommend checking the unit tests.

Regards,
Dan.

-----Original Message-----
From: fdo-users-bounces at lists.osgeo.org [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Geoffrey Curtis
Sent: Tuesday, June 26, 2012 9:35 AM
To: fdo-users at lists.osgeo.org
Subject: Re: [fdo-users] FDO Usage Questions

Thanks for taking the time to reply.

1.) The DescribeSchema command can take ages in comparison to the GetClassNames command.  Not sure why exactly, but i definitely would like to avoid/defer the overhead we are seeing with that command if possible.

4.) Was reading some past posts that mentioned using the SQL commands to avoid some of the overhead here.  Will have to take a look and see if that will work for what i need.  For now response time would have higher priority over being generic like i wanted.

5.) Well this one was weird to me, mainly because the SchemaElement parent pointer is not reference counted.  So even if i originally got the reference through DescribeSchema, if i only hold onto the FeatureClass reference, it's parent becomes invalid afterwards.  Guess i will have to simply modify things to store the Schema pointer as well.  But having a reference to a feature class definition and it not tracking its parent Schema seems inconvenient as just because two definitions have the same name doesn't mean their definitions are in any way similar.  That means there is no way to get the original referencing Schema from any of the methods or queries that only return FeatureReader references.  Given it takes a qualified name to query for a FeatureReader when there are duplicate names, i figured it would know its Schema, but i guess again i should just keep the name around.

-

i  need to find a good reference on the supported SQL commands necessary to do what is needed.

Simple things like table retrieval and record counting is simple, and fast, as I would expect it to be (don’t know why it is so much slower through FDO).  New to the GIS related commands though so I do not know all the ones I need to access data the way I would like.

The SpatialExtents function through SelectAggregates is very slow, almost as bad as simply reading the Geometries.

If the above tests are any indication, if i can get things to work successfully through SQL i should be all set.

Thanks for the information.


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