HHH-19555 tests and doc

[gavinking]

@SQLRestriction on a @ManyToOne @JoinTable is currently mostly-working, by accident.

This PR documents this possibility, and adds tests for it.

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https://hibernate.atlassian.net/browse/HHH-19555

[gavinking]

Fails on databases with merge emulation due to this condition in OptionalTableUpdateOperation:

if ( valuesAnalysis.getTablesWithPreviousNonNullValues().contains( tableMapping ) ) {

[jrenaat]

@gavinking rebased the upsert impls for edb and hsql, and disabled the test for sybase. All tests green now. Over to you 👍

[gavinking]

Nice! Thanks man!

We need to think what to do about Sybase (i.e. produce an error at startup or whatever, not quite sure.)

[jrenaat]

Nice! Thanks man!

We need to think what to do about Sybase (i.e. produce an error at startup or whatever, not quite sure.)

Add an supportsSqlRestrictionOnJoinTableManyToOne by default true except for Sybase dialects in Dialect ?

[yrodiere]

Nice! Thanks man!
We need to think what to do about Sybase (i.e. produce an error at startup or whatever, not quite sure.)

Add an supportsSqlRestrictionOnJoinTableManyToOne by default true except for Sybase dialects in Dialect ?

Maybe rather supportsUpsert (or whatever it's named, it probably exists) + an error message stating that it's only supported on database with upsert support?

WDYT @gavinking?

[gavinking]

There's a comment on the issue:

I have found a second problem with this.
All is well as long as such an association is fetched eagerly using a join.
But for LAZY fetching, the restriction is never applied.
So I would need @mbellade to help us repurpose the stuff done for @ConcreteProxy to add an extra “look-ahead” join with the restriction. I attempted to make this work myself, but I failed.

I'm not sure that this problem has been addressed yet. I'm guessing not. I don't think we can merge this until that part of it is done.

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[gavinking]

Alright, so, based on my testing, we have two options here:

1. disable this functionality for the two cases where we know it's currently broken:
   • fetch=LAZY, and
   • Sybase
2. disable on Sybase, and fix the problem with lazy fetching by repurposing the @ConcreteProxy-style lookahead.

Apparently I tried to do 2 when I first looked at this, and couldn't figure it out, so we would need Marco's help on it.

Anyway, I have added tests.