Karel Zak <zakkr@zf.jcu.cz> writes:
> On Tue, Apr 06, 2004 at 10:33:25AM -0400, Tom Lane wrote:
>> This isn't simply a matter of "omitting the sort".
> I didn't talk about "Append" result, but about "Unique" result. The
> ORDER BY in UNION query works with final concanated data -- that's
> right. My question is why a result from this ORDER BY is again sorted:
Oh, okay, that's just something that never got done, per this old
comment:
/* * We set current_pathkeys NIL indicating we do not know sort * order. This is correct when the
topset operation is UNION * ALL, since the appended-together results are unsorted even if * the subplans
weresorted. For other set operations we could be * smarter --- room for future improvement! */
I've committed changes to do the right thing in CVS tip.
regards, tom lane
