I started work on SQM-24 which covers translation of criteria queries into SQM.
The difficulty with this is that the JPA contracts alone do not give enough information to really be able to understand the semantics of the query; there is just not enough information exposed. I can get into specific examples if that helps, but for now lets take that as a given... So then how do we go about translating a criteria into an SQM? There are going to be 2 main approaches. Each requires some level of extension to the standard contracts: The first approach is to use visitation. The criteria nodes would be expected to implement an SQM extension accepting a visitor and do the right thing. The gains here are the normal gains with the visitor pattern. The downside is that this makes SQM highly dependent on the criteria impl doing the right thing and makes the criteria impl sensitive to SQM (depending n how we expose the visitation methods to a degree). The second approach would be to extended the standard criteria contracts to more fully cover the semantic. As one example, JPA defines just Predicate (for the most part) without exposing the type of predicate. Is it a LIKE expression? A BETWEEN? A Comparison (=, !=, <, etc)? We just don't know from the standard contracts. So we'd have to develop a full semantic extension model here. `interface LikePredicate extends Predicate`, `BetweenPredicate extends Predicate`, etc. I lean towards the visitor approach given these choices. Anyone else have opinions? Other options? _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
