I agree. Its my biggest hang up with regard to using Antlr 4. Actually, its my only hang up with Antlr 4, but its a huge one.
On Tue, Aug 18, 2015 at 9:30 AM andrea boriero <drebor...@gmail.com> wrote: > 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
