[fdo-users] FDO Usage Questions
geoffrey.curtis at pds.nl
Wed Jun 20 06:59:48 PDT 2012
i have a few questions with regard to the usage and design of the FDO
We currently have a working implementation setup and can successfully
retrieve the feature class data we require, but at times the access to the
information seems slow or lacking from an end-user stand point.
If it helps, this is currently with regard to the ArcSDE provider, but we
may have others implemented in the future.
1.) Is there a way to query the number of feature classes? The number of
entries in a FeatureReader?
2.) Currently using the GetClassNames command returns all Class definitions
within Schemas. Is there a way to filter this to just Feature Class
definitions? The DescribeSchema command can be slow, and does more than I
need initially from a UI perspective.
Without initial counts, at times i can't do more than simply throw up a Busy
cursor instead of a proper progress bar or other informative UI.
3.) Are there ways to filter Feature Classes by Coordinate System? What are
the correct ways to filter Feature Classes by Extent?
4.) What are the proper ways to get the extents of a Feature Class? Using
the SpatialExtents function with the SelectAggregates command seems to work,
but at times can seem to take as long as retrieving the Geometry data
through the FeatureReader interface.
5.) Are Schema definitions persistent? Accessing the GetQualifiedName
method has caused a number of exceptions with methods because the parent of
a FeatureClass seems to have gone out of scope after retrieving it. It
seems strange to be able to query for a FeatureClass or FeatureReader by
name and not be able to rely on getting the proper qualified name back.
6.) More out of curiosity: Is there any documentation on the classes that
are supposed to be treated as reference counted? Since raw pointers are
returned everywhere we have run into a couple of cases where the return
value was actually not intended to be used with FdoPtr, even though it is
actually derived from FdoIDisposable (the FdoProviderCollection returned
from FdoProviderRegistry::getProviders() for example). Just wanted to make
sure there were not any others.
7.) Are there any other things i may have missed that could possibly improve
the response times of these commands?
Given the number of back-end implementations that seem to be based on
databases, some of these i would have figured to be rather simple tasks, but
i am not sure if i am looking in the right place to find other alternatives
to the methods we are currently using.
Thanks in advance.
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