[fdo-users] FDO Usage Questions

Geoffrey Curtis geoffrey.curtis at pds.nl
Tue Jun 26 06:35:04 PDT 2012

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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