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)
impl from scratch.
On Thu, Aug 27, 2015 at 8:45 AM Gunnar Morling <gunnar(a)hibernate.org> wrote:
2015-08-26 14:41 GMT+02:00 Steve Ebersole
> On Wed, Aug 26, 2015 at 2:10 AM Gunnar Morling <gunnar(a)hibernate.org>
>> Hi Steve,
>> > The other approach is to use a 3-phase translation (input
>> > -> semantic-tree -> semantic-SQL-tree(s) -> SQL). This gives a
>> > 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
>> 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
> query" case I mentioned elsewhere (a query like 'from
> 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
> I have a QuerySplitter that takes that query and makes a copy of that
> SQM tree, one for each mapped implementor of the specified class. FWIW,
> does this today, albeit in a different way. Today we split the query
> on String manip and then feed it parser. Here we feed it to the parser
> use the tree to split it; much less brittle :)
> Really the cases where this would happen (one "concrete SQM" ->
> 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
>> 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
> 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
> 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
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
> JPQL compliance" enforcement.