I have nothing against your proposal so +1 On 24 August 2015 at 04:55, Steve Ebersole <st...@hibernate.org> wrote:
> Another point I want to discuss up from because it affects tree > structure. Specifically the idea of an "unbounded implicit inheritance" > query. These are queries like "from java.lang.Object". Queries where the > from clause pulls in "unmapped inheritance". These are fine, to an > extent. Hibernate has natively supported these since way back[1]. > > What is problematic is cases where we have more than one "unmapped > inheritance" reference. E.g. "from java.lang.Object o1, java.lang.Object > o2". In fact its the same difficulty as an unbounded cartesian product, > but here in terms of the number of SQL queries we need to produce/execute. > > So I propose that we allow just one "unmapped inheritance" reference per > query. > > [1] Reminder to self... another "strict JPQL compliance" consideration. > > On Sat, Aug 22, 2015 at 1:16 PM Steve Ebersole <st...@hibernate.org> > wrote: > >> I got that initial refactoring pushed to my fork... >> >> On Fri, Aug 21, 2015 at 3:51 PM Steve Ebersole <st...@hibernate.org> >> wrote: >> >>> 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 <drebor...@gmail.com> >>> wrote: >>> >>>> I haven't seen it, I'm going to read it. >>>> >>>> On 21 August 2015 at 16:54, Steve Ebersole <st...@hibernate.org> 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 <st...@hibernate.org> >>>>> 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 <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
