Greg Stark <gsst...@mit.edu> writes: > The first step is probably to do the opposite of what we're talking > about here: cases where people *have* added extra columns to the GROUP > BY key so they can use those columns in their select list. We can > remove those columns from the sort or hash comparison key if there's a > column (or columns) which is a unique constraint key for the same > source. Similarly we can remove columns from an ORDER BY if the order > key has earlier columns which are already a unique key for the same > source.
This is something we could only do at plan time --- if we do it at parse time we risk making a robust query into one that will break when somebody drops a constraint. So it's not really the inverse of the other case. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers