From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Theo Kramer <theo(at)flame(dot)co(dot)za> |
Cc: | hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Index scan? |
Date: | 1999-08-13 17:50:43 |
Message-ID: | 5415.934566643@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Theo Kramer <theo(at)flame(dot)co(dot)za> writes:
> Tom Lane wrote:
>> We need to push awareness of the output ordering requirement down into
>> the code that chooses the basic plan. It's on the TODO list (or should
>> be) but I dunno when someone will get around to it.
> I can't wait :-)
I am about to do some major hacking on the planner/optimizer's
representation of path sort orders (for anyone who cares, PathOrder data
is going to be merged into the pathkeys structures). After the dust
settles, I will see what I can do with this issue --- it might be pretty
easy once the data structures are cleaned up.
Aside from the case with an ORDER BY clause, I believe the planner is
currently too dumb to exploit a pre-sorted path for GROUP BY. It
always puts in an explicit sort on the GROUP BY keys ...
regards, tom lane
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