[Sqlalchemy-tickets] Issue #3555: Extract a record's field (zzzeek/sqlalchemy)

[Andrey S. <iss...@bi...>]

New issue 3555: Extract a record's field
https://bitbucket.org/zzzeek/sqlalchemy/issues/3555/extract-a-records-field

Andrey Semenov:

I need to construct a query like
```
#!sql
SELECT (jsonb_each('{"a": 1, "b": 2}')).key

```
`jsonb_each()` returns a RECORD type which in turn has it's own fields named `key` and `value`. Yes, in PostgreSQL it MUST be also wrapped into braces, because of extraction and executing precedence (or it will try to select a `key` column from the `jsonb_each()` column - that leads to SQL engine error raised). It's not obvious how to query those fields while constructing a query (or make a dot-notated reference to a custom sub-field when this capability is provided by an engine).

Also, dialects.util.dottedgetter does not work with func.* (returns None if called against)