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Next message Steve Norman  posted on Friday, June 25, 2010 - 06:44 pm
I was wondering, under DDS- if I have a union of two structures, is it possible to have an instance key inside each structure, or does the instance key have to be outside the union?
Next message Erik Hendriks  posted on Monday, June 28, 2010 - 09:32 am
Hi Steve,

The DDS specification does not specify which type of key-fields must be supported by a DDS implementation, so different implementations might have different levels of support for the more 'unconventional' key definitions.

Putting keys inside a union makes up for a very exotic key definition: complicating the storage algorithms and also impacting SQL based filters (which have no official syntax to address a branch within a union). I think for that reason you will not easilty find a DDS implementation that supports key-fields inside a union.

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