Nevermind. I will not do that. I think I have found a still-easyish way to do it.
On Thu, Aug 27, 2015 at 10:57 AM Steve Ebersole <st...@hibernate.org> wrote: > I do want to pull ORM in to the hibernate-sqm module as a test dependency > to be able to more easily set up the ModelMetadata stuff based on a > SessionFactory. That is possibly awkward later when we then use > hibernate-sqm in ORM in terms of having 2 different versions of ORM. I am > open to alternatives that don't involve *me* developing a real(ish) > ModelMetadata > impl from scratch. > > On Thu, Aug 27, 2015 at 8:45 AM Gunnar Morling <gun...@hibernate.org> > wrote: > >> 2015-08-26 14:41 GMT+02:00 Steve Ebersole <st...@hibernate.org>: >> > On Wed, Aug 26, 2015 at 2:10 AM Gunnar Morling <gun...@hibernate.org> >> wrote: >> >> >> >> Hi Steve, >> >> >> >> > 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. >> >> >> >> In which situations will this happen? I can see inheritance where a >> >> HQL query targeting a super-type needs to be translated into a SQL >> >> query per sub-type table. What others are there? >> > >> > >> > For ORM the only time this happens today for a SELECT query is in the >> "split >> > query" case I mentioned elsewhere (a query like 'from >> java.lang.Object'). >> > SQM does this much better than we do in ORM today. in SQM we build a >> > semantic tree that encodes the "unmapped polymorphism" such that we get >> a >> > tree with 'java.lang.Object' as the root from element. But it is a >> > FromElement with a special type of EntityTypeDescriptor (which comes >> from >> > the caller remember): PolymorphicEntityTypeDescriptor. On the ORM side >> then >> > I have a QuerySplitter that takes that query and makes a copy of that >> entire >> > SQM tree, one for each mapped implementor of the specified class. >> FWIW, ORM >> > does this today, albeit in a different way. Today we split the query >> based >> > on String manip and then feed it parser. Here we feed it to the parser >> and >> > use the tree to split it; much less brittle :) >> > >> > Really the cases where this would happen (one "concrete SQM" -> multiple >> > SQL) would be UPDATE and DELETE queries against "multi-table structures" >> > (inheritance, secondary tables). >> > >> > >> >> For the purposes of OGM this phase ideally would not be tied to SQL, >> >> as we phase the same task with non-SQL backends in SQL. I.e. i'd be >> >> beneficial to have input -> semantic-tree -> >> >> semantic-output-query-tree(s) -> (SQL|non-SQL query). There >> >> "semantic-output-query-tree(s)" would be an abstract representation of >> >> the queries to be executed, e.g. referencing the table name(s). But it >> >> would be unaware of SQL specifics. >> > >> > >> > OGM would be doing this. This SQM is the end result of the shared >> library. >> > WHat each caller does with the SQM is up to that particular caller. We >> > should consider moving QuerySplitter (its in my PoC, which now acts as >> the >> > PoC for using this in ORM) into the hibernate-sqm module. Any caller >> > wanting to support those unmapped class references will need to do the >> same >> > thing. >> >> Yes, that'd be good I think. We'd have to apply the same rules for >> splitting as ORM. >> >> > >> > BTW, another cool thing to note is the (still expanding) support for >> "strict >> > JPQL compliance" enforcement. >> > _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
