[DISCUSSION] More SqlLogicTest test coverage for queries, including join queries

[findepi]

During SDF's upgrade to DataFusion 43 we found a bug #13425 . This was possible thanks to extensive test coverage for certain query shapes that we have internally, which is good. The bad part is that the bug could be caught at the PR stage, or before the release, should similar tests exist in DataFusion project.

Would it be useful if there were more SLT query tests, including the ones that allowed to catch #13425?

cc @alamb @schulte-lukas @gliga

[alamb]

Yes, 100% I think adding additional test coverage in all areas would be super helpful

We / I also regularly hit bugs that are caught by InfluxData's test suite during upgrades of DataFusion but were not caught during the DataFusion PR

Other Areas that would benefit from improved testing from my experience:

1. Metadata handling (like attaching field level metadata, etc)
2. UNION coverage (which we use extensively)
3. Dictionary handling (which we also use a lot)