Horton

Re: Memory usage during sorting

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Stark <stark@mit.edu>
Cc: Robert Haas <robertmhaas@gmail.com>, Jeff Janes <jeff.janes@gmail.com>, Hitoshi Harada <umi.tanuki@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2012-03-20T16:12:37Z
Lists: pgsql-hackers

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  1. Improve performance of our private version of qsort. Per recent testing,

  2. Further performance improvements in sorting: reduce number of comparisons

Greg Stark <stark@mit.edu> writes:
> http://en.wikipedia.org/wiki/Binary_heap#Building_a_heap

Interesting.  I'm pretty sure that idea appears nowhere in Knuth
(which might mean it's new enough to have a live patent on it ...
anybody know who invented this?).  But it seems like that should buy
back enough comparisons to justify leaving the next-run tuples out of
the heap (unordered) until the heap becomes empty.  You still want to
insert new tuples into the heap if they can go to the current run, of
course.

			regards, tom lane