| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Marti Raudsepp <marti(at)juffo(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thom Brown <thom(at)linux(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: B-Tree support function number 3 (strxfrm() optimization) |
| Date: | 2014-09-30 05:34:28 |
| Message-ID: | CAM3SWZT+V3LLRBSCyUJ9jOvuMDpBq6bUpF9woFBfuyWgwuHW3A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Sep 25, 2014 at 1:36 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> (concerns about a second sortsupport state)
I think I may have underestimated the cost of not have
sorttuple.datum1 with a pointer-to-text representation available in
cases such as the one you describe.
Attached revision introduces an alternative approach, which does not
have a separate sortsupport state struct. In the event of aborting
abbreviation, we go back and fix-up datum1 to have a consistently have
a pointer to text representation, making a comparator swap safe - at
that point, it's as if abbreviation was never even considered (apart
from the cost, of course). We still need a special tie-breaker
comparator, though.
I hope this addresses your concern.
--
Peter Geoghegan
| Attachment | Content-Type | Size |
|---|---|---|
| 0001-Abbreviated-sortsupport-keys.patch | text/x-patch | 53.6 KB |
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