[hibernate-dev] Treat support

Hello, I am sorry if this was already discussed somewhere but I couldn't find anything on the internet about this. I am currently working on some testcases for the treat operator(https://github.com/beikov/jpa-treat-variations) that are apparently missing in the TCK as most JPA providers fail them. I'd like to offer them to you to be integrated into the hibernate testsuite. Could you maybe run that locally and comment on the test cases? I am not 100% sure that my understanding of what treat should do is right, but I tried to explain the reasoning for the expected test results inline. The following points I found out during my testing. * Missing support for treated paths like "TREAT(...).property" in the parser. This is more or less workaroundable for non-root path treats. Since root paths can't be treat joined to my knowledge, some treated paths simple can't be used. Maybe in 90% of the cases hibernate will just resolve to the right property without needing the treat? * Missing support for a special case of treat join which apparently was overseen by the JPA spec which would be "TREAT(TREAT(rootPath AS Subtype).relation AS RelationSubtype)". Eclipselink not only allows this syntax but for inner joins also implements the appropriate logic. I am thinking that this might even work in hibernate without the inner treat, but would fail for attributes with same names. * Joins for supertypes and conditions on discriminators are not aware of the join type actually used in the treated join => left join should cascade up the type hierarchy and discriminator checks should contain OR DTYPE IS NULL for left join semantics. If treats are in subconditions the DTYPE checks might even be wrong * Joins are generated for the whole hierarchy not only the types that are treated => this might seem to be "just" a performance problem, but IMO actually is a correctness problem as it makes a difference if you get e.g. 2 rows or 2 * TYPES rows especially for count queries. What I would like to know is if these bugs are planned to be tackled in Hibernate 6+ only or if they are considered for 4.3, 5.0, 5.1, 5.2 too. Are these things too hard to fix without SQM or do capable people just lack time or interest to implement this? -- Mit freundlichen Grüßen, ------------------------------------------------------------------------ *Christian Beikov*