feat(risingwave): support struct field access

[christophediprima]

Description of changes

Add a specific visit method for RisingWave visit_StructField.

"f{idx}" is not supported like in Postgres.

Use dot and parenthesis annotation as dots only is not working on the first level.

`dataframe.metadata["user.profile.link"].value.url``

Will be translated to:

`(((("t1"."metadata")."user.profile.link").value).url)``

Issues closed

• Resolves #11182

[cpcloud]

This is somewhat tricky because of the way risingwave encodes struct types.

[christophediprima]

Thanks for your reply @cpcloud. I don't really get what is the issue with the test that is failing. Can you briefly explain?

[cpcloud]

I think I managed to get a first version of this working (meaning passing all existing tests without changing the tests).

[christophediprima]

@cpcloud looks great! Thanks a lot for pushing this forward and getting the tests to pass! I know this PR wasn’t fully complete, so your help in finishing things up is much appreciated.

[cpcloud]

There are some complications here :)

1. RisingWave's DESCRIBE returns a shredded schema, which would be fine if it actually segmented field names for fields in structs like this: STRUCT<"a.b.c" INT>. Currently it does not.
2. I tried querying information_schema.columns, but that has the same problem: it returns the struct with unquoted fields, and sqlglot is not and will not handle the unquoted fields.

I think the changes need to come from RisingWave, in the form of quoting field names in whatever schema metadata is returned.

[cpcloud]

Moving to draft until there's a risingwave release with their changes.

[christophediprima]

Hi there! Can we reopen that one? :)

[cpcloud]

Going to do this in a separate, new PR.