Re: index-only scans - Mailing list pgsql-hackers

From Kevin Grittner
Subject Re: index-only scans
Date
Msg-id 4E45573E020000250003FE9B@gw.wicourts.gov
Whole thread Raw
In response to Re: index-only scans  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: index-only scans
List pgsql-hackers
Robert Haas <robertmhaas@gmail.com> wrote:
> That's one of the points I asked for feedback on in my original
> email.  "How should the costing be done?"
It seems pretty clear that there should be some cost adjustment.  If
you can't get good numbers somehow on what fraction of the heap
accesses will be needed, I would suggest using a magic number based
on the assumption that half the heap access otherwise necessary will
be done.  It wouldn't be the worst magic number in the planner.  Of
course, real numbers are always better if you can get them.
-Kevin


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