What is the desired behaviour for Database backends on Nothing * Nothing

[radeusgd]

Currently, e.g. on Postgres an expression Nothing * Nothing results in operator is not unique: unknown * unknown.

The created SQL is correct (NULL * NULL) but the database does not like unknown types.

Do we:

1. keep it as is, as it's a DB specific behaviour?
2. try to glue it to avoid errors - replace the operation in SQL with NULL constant?

I guess (2) will be more user-friendly and consistent with in-memory backend.

[GregoryTravis]

How do the other DBs handle this?

[radeusgd]

How do the other DBs handle this?

Snowflake and SQLServer both seem to accept the operation and simply return NULL.

So it seems that the issue may only be with Postgres.

[radeusgd]

Before this can be implemented we need to address #11757

[radeusgd]

Since in #11757 we decided that Null columns won't be required in DB backends, so this issue is no longer relevant.

[radeusgd]

Updated tests are merged into the #11737 PR.