On 14/11/14 00:46, Simon Riggs wrote:
> Limit  (cost=.... rows=20 width=175) (actual time=.... rows=20 loops=1)
>    ->  Sort  (cost=.... rows=568733 width=175) (actual time=....
> rows=20 loops=1)
>          Sort Method: top-N heapsort

Going off on a tangent, when I was playing with a merge-sort
implementation I propagated limit information into the sort
node, for a significant win.  Eliding the Limit node gave
a further slight win.

I wasn't convinced the use-case was common enough to justify
the replacement of quicksort (despite having consistently
fewer compares, the merge sort was slightly slower.  I never
understood why) - but I never asked.  Is there any appetite
for supporting alternate sort algorithms?

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