Re: [hibernate-dev] Hibernate ORM SQL generation

Just a heads up that I started a major refactoring of the antlr4 poc project in preparation for starting to look at this next sql-gen step. First I am making it into a multi-module project. We will have the hql-parser module, but then also an orm-sql-gen module to be able to play with that part. This makes sure we are not blending orm concerns into the pure hql parser. Also, I started working on splitting the "semantic query" model out into a separate module as well. There are a few reasons for this. I wont go into them all here. The main one being that HQL is just one producer of this semantic model. Rather than another long name I went with the acronym SQM (Semantic Query Model) here. The top package being org.hibernate.sqm. These changes already illustrated some tighter couplings then I had intended, so it was a good exercise. I'll push once I get those couplings cleaned up. On Fri, Aug 21, 2015 at 2:35 PM andrea boriero <dreborier(a)gmail.com&gt; wrote: > I haven't seen it, I'm going to read it. > > On 21 August 2015 at 16:54, Steve Ebersole <steve(a)hibernate.org&gt; wrote: > >> http://www.antlr2.org/article/1170602723163/treewalkers.html >> >> Not sure if y'all have seen this. Its an old article advocating manual >> tree walking (what we are facing here) over using generated tree walkers. >> >> >> >> On Wed, Aug 19, 2015 at 12:27 PM Steve Ebersole <steve(a)hibernate.org&gt; >> wrote: >> >>> 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 <dreborier(a)gmail.com&gt; >>> 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 <steve(a)hibernate.org&gt; >>>> 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(a)lists.jboss.org >>>>> https://lists.jboss.org/mailman/listinfo/hibernate-dev >>>>> >>>> >>>> >