Surfacing system columns xmin, xmax, etc in views?

[aschleck]

In postgres every table has a number of additional columns: https://www.postgresql.org/docs/9.1/ddl-system-columns.html

They are useful in some situations, for example I use xmax to detect conflicts when inserting objects with randomly generated, human readable IDs.

        INSERT INTO objects (
          id,
          created,
          location
        ) VALUES ($1, CURRENT_TIMESTAMP, $2)
        ON CONFLICT (id) DO NOTHING
        RETURNING (xmax = 0) AS conflict_free

Then I can check conflict_free in my application logic and retry with a new ID if it's set. I suppose the other way to do this is to drop the ON CONFLICT DO NOTHING but now I have to catch the exception, verify it failed due to the conflict and not some other problem, and retry etc. Overall I think it's better to do this than to handle control flow via exceptions.

Anyway, with reshape views, none of these columns are available. Would it be reasonable to surface any of these system columns? They don't seem problematic to me but I'm not very familiar with how reshape works under the hood.