"Tom Lane" <[EMAIL PROTECTED]> writes: > select random() as a, random() as b from foo order by b, a; > > And it definitely seems the wrong thing for the last one.
Ouch. > What I'm thinking of doing is adding a field to EquivalenceClass that > carries the ressortgroupref of the originating ORDER BY key's targetlist > entry, in the case where the EquivalenceClass came from building a > PathKey for ORDER BY. Then, if the EquivalenceClass is ec_volatile, > we insist on matching that rather than matching the expression tree. > This wouldn't affect the behavior for ordinary non-volatile sort keys, > for which expression equivalence is valid. What if the equivalence class is in more than one place in the ORDER BY? I suppose GROUP BY has the same problem? And what would happen when you pull up subqueries? > If we wanted cases 1 and 2 to behave differently, it'd be better to have the > parser always generate resjunk columns for ORDER BY expressions, and get the > planner to collapse out columns that are redundant. But that seems too big a > change to contemplate for 8.3. That clearly sounds right. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training! ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
