I wrote: > Yeah, I didn't have any doubt that it was real. Still don't know > why my test case isn't doing what I expected, though.
Doh: the planner knows that transaction_timestamp() is stable, so it concludes that the DISTINCT condition is vacuous. There is a "Unique" node in the plan, but it has zero columns to compare, so it thinks the tuple are all equivalent and emits only the first. I had noticed that there was no "Sort" node, but failed to realize that that implied the "Unique" node was degenerate. Maybe this is over-optimization, but I think we'd be very sad if the planner didn't do it; getting rid of useless sort columns is critical in a lot of situations. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers