yes Steve I'm more familiar with Antlr4 ( but not 3) and I gave a look at your poc.
Apart some problems to fully understand the semantic model (due to my lack of a complete knowledge of the domain problem), I agree with you about the simplicity and elegance of the grammar for HQL recognition and semantic model building. What I don't like it's the necessity to build our own semantic model walker/s in order to produce the final SQL. On 14 August 2015 at 16:32, Steve Ebersole <st...@hibernate.org> wrote: > We've had a few discussions about this in the past. As 5.0 is getting > close to Final (next week), its time to start contemplating our next major > tasks. The consensus pick for that has been the idea of a "unified SQL > generation engine" along with a shared project for the semantic analysis of > HQL/JPQL (and recently it was decided to include JPA Criteria > interpretation here as well). > > The central premise is this. Take the roughly 6 or 7 different top-level > ways Hibernate generates SQL and combine that into one "engine" based on > the input of a "semantic tree". The mentioned HQL/JPQL/Criteria shared > project will be one producer of such semantic trees. Others would include > persisters (for insert/update/delete requests) and loaders (for load > requests). > > We have a lot of tasks for this overall goal still remaining. > > We still have to finalize the design for the HQL/JPQL/Criteria to semantic > tree translator. One option is to proceed with the Antlr 4 based approach > I started a PoC for. John has been helping me some lately with that. The > first task here is to come to a consensus whether Antlr 4 is the way we > want to proceed here. We've been over the pros and cons before in detail. > In summary, there is a lot to love with Antlr 4. Our grammar for HQL > recognition and semantic tree building is very simple and elegant imo. The > drawback is clearly the lack of tree walking, meaning that we are > responsible for writing by hand our walker for the semantic tree. In fact > multiple, since each consumer (orm, ogm, search) would need to write their > own. And if we decide to build another AST while walking the semantic > tree, we'd end up having to hand-write yet another walker for those. > > What I mean by that last part is that there are 2 ways we might choose to > deal with the semantic tree. For the purpose of discussion, let's look at > the ORM case. The first approach is to simply generate the SQL as we walk > the semantic tree; this would be a 2 phase interpretation approach (input > -> semantic tree -> SQL). That works in many cases. However it breaks > down in other cases. This is exactly the approach our existing HQL > translator uses. The other approach is to use a 3-phase translation (input > -> semantic-tree -> semantic-SQL-tree(s) -> SQL). This gives a hint to one > of the major problems. One source "semantic" query will often correspond > to multiple SQL queries; that is hard to manage in the 2-phase approach. > And not to mention integrating things like follow-on fetches and other > enhancements we want to gain from this. My vote is definitely for 3 or > more phases of interpretation. The problem is that this is exactly where > Antlr 4 sort of falls down. > > So first things first... we need to decide on Antlr 3 versus Antlr 4 > (versus some other parser solution). > > Next, on the ORM side (every "backend" can decide this individually) we > need to decide on the approach for semantic-tree to SQL translation, which > somewhat depends on the Antlr 3 versus Antlr 4 decision. > > We really need to decide these things ASAP and get moving on them as soon > as ORM 5.0 is finished. > > Also, this is a massive undertaking with huge gain potentials for not just > ORM. As such we need to understand who will be working on this. Sanne, > Gunnar... I know y'all have a vested interest and a desire to work on it. > John, I know the same is true for you. Andrea? Have you had a chance to > look over the poc and/or get more familiar with Antlr? > _______________________________________________ > hibernate-dev mailing list > hibernate-dev@lists.jboss.org > https://lists.jboss.org/mailman/listinfo/hibernate-dev > _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
