[fdo-internals] New FDO RFC 50 posted - Extend FDO API to Select from Multiple Classes and Select Joins

[Orest Halustchak]

Hi,

Please have a look at a new FDO RFC 50 that proposes to extend the FDO api to support the ability to use multiple classes in a select and in a filter. This would provide the ability the express joins at the fdo level.

http://trac.osgeo.org/fdo/wiki/FDORfc50

It is a common capability that users need, the ability to join together two or more classes for a result to support analysis, rendering, or other uses. Until now, with FDO, this was done at a higher level such as the client-side join capabilities within MapGuide. While that capability is useful, it does not perform well and is error prone. This enhancement provides us a clear way to push that capability down to providers that support it such that they can translate the join into native server expressions. In general, I think it adds more power and flexibility to the FDO api.

As usual, this includes capability functions so that applications can discover if a provider supports this. We don't expect all providers to support this, mainly the ones that pass through fdo queries to sql.

I hope you like it. :)

Thanks very much to Romy Dascalescu for putting this together and trying out various alternatives.

Please provide your comments and suggestions.

Thanks,
Orest.

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