Re: [Objectbridge-developers] OJB Homepage, OQL

[David W F. <dw...@la...>]

QBE, however, does not deal very well with query filters (like
inequality, similarity).  There should be explicit support for that
(which would map directly to an OQL statement).

Dave

Thomas Mahler writes:
 > Thanks for all your comments regarding OQL and Query by Example (QBE)
 > facilities.
 > 
 > IMHO it's the best solution to start with a QBE-facility and only after
 > that provide an OQL API.
 > Starting with QBE has 2 advantages:
 > - It will provide a useful extension to the PersistenceBroker, so that
 > it can be used even without the ODMG server
 > - there are some working examples from other projects, that can be
 > easily adopted to our needs
 > 
 > Implementing OQL on top of such a facility will work licke follows:
 > - implement a parser that reads OQL-queries and generates query trees.
 > - provide a mapping from the abstract query trees to QBE query objects.
 > 
 > alternatively one could try to build a parser that directly generates
 > QBE query objects.
 > 
 > I will have a look at all the projects you mentioned to find the best
 > possible start for the QBE facility. I liked the SODA approach
 > (www.db4o.com), but I think they are not finished with their spec.
 > 
 > I'll start with this asap. Right now I'm doing some performance tuning
 > deep inside the PersistenceBroker. I'm profiling OJB excution with the
 > java -Xrunhprof option which gives me some hints about execution hot
 > spots. I already identified some hot spots in the metadata layer... 
 > 
 > regards,
 > 
 > Thomas
 > 
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