HHH-19497 Addresses major issue fallback implementation of "in list" predicate

[michaelfranz]

When a NOT is applied to an IN, such as
cq.select(root).where(root.get("customerType").in(List.of(i1, i2)))
and when i1, i2 are represented by more than one column or formula (let's call these a and b), the previous implementation emitted:
(a <> ? or b <> ?) or (a <> ? or b <> ?) or ...
when the correct expression needs to be:
not ((a = ? and b = ?) or (a = ? and b = ?) or ...)

The previous implementation incorrectly distributes the negation to each item in the list. De Morgan 101. The predicate is logically incorrect and this can lead to unpredictable results, which can even include ALL the records being returned from a table. Very, very bad.

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https://hibernate.atlassian.net/browse/HHH-19497

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[gavinking]

As I mentioned on the issue report, there's two ways to fix this problem:

1. the way you've chosen, which is to just use not, or
2. alternatively, by replacing the incorrect ors with ands.

I'm not sure why the code was written to distribute the not and using <> instead of =. But it seems strange that it would have been written that way without some good reason. So we need to understand why it was written like that. @beikov, do you know?

[gavinking]

In the meantime, please:

1. add a test, and
2. squash the commits.

[michaelfranz]

In the meantime, please:

1. add a test, and
2. squash the commits.

I'm new to the project and I'm unsure about the right way to provide a test. My discovery of the issue came from a client's Hibernate 6 / DB2-environment. I verified the solution outside of this environment by overriding H2Dialect and H2SqlAstTranslator with implementations that force the issue to come to light. Therefore, though I appreciate it's not ideal, I attached all the relevant artefacts to the original JIRA ticket.

If someone would can point me to guidance on how to add a suitable test to the project, then I will do so if I find the time. In the meantime, I've provided everything I have.

As I mentioned on the issue report, there's two ways to fix this problem:

1. the way you've chosen, which is to just use not, or
2. alternatively, by replacing the incorrect ors with ands.

I'm not sure why the code was written to distribute the not and using <> instead of =. But it seems strange that it would have been written that way without some good reason. So we need to understand why it was written like that. @beikov, do you know?

The "good reason", I suppose, is that it is marginally more optimal to do it in that way. I went for the "not" because it's more intuitive. I prioritised correct logic over optimisation. I'll leave it to regular contributors to decide which way they want to take it from here.

[gavinking]

The "good reason", I suppose, is that it is marginally more optimal to do it in that way.

If it's true that it's marginally more optimal, then we should always do things in the marginally more optimal way.

But I don't see an obvious reason why it would be, so I would prefer to wait for Christian to chime in.

If someone would can point me to guidance on how to add a suitable test to the project, then I will do so if I find the time. In the meantime, I've provided everything I have.

To be clear: a test is an absolute hard requirement. We never fix bugs in Hibernate without a test, and every bugfix must be accompanied by a test.

There is a template here: https://github.com/hibernate/hibernate-test-case-templates