Re: B-Tree support function number 3 (strxfrm() optimization) - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: B-Tree support function number 3 (strxfrm() optimization)
Date
Msg-id CAM3SWZRe5-JizUdvHRiJuZEQY2Va-ddREPEMhosnedvdDVFuJQ@mail.gmail.com
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In response to Re: B-Tree support function number 3 (strxfrm() optimization)  (Peter Geoghegan <pg@heroku.com>)
Responses Re: B-Tree support function number 3 (strxfrm() optimization)
List pgsql-hackers
On Tue, Jan 20, 2015 at 3:57 PM, Peter Geoghegan <pg@heroku.com> wrote:
> It's certainly possible to fix Andrew's test case with the attached.
> I'm not sure that that's the appropriate fix, though: there is
> probably a case to be made for not bothering with abbreviation once
> we've read tuples in for the final merge run. More likely, the
> strongest case is for storing the abbreviated keys on disk too, and
> reading those back.

Maybe not, though: An extra 8 bytes per tuple on disk is not free.
OTOH, if we're I/O bound on the final merge, as we ought to be, then
recomputing the abbreviated keys could make sense, since there may
well be an idle CPU core anyway.

-- 
Peter Geoghegan



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