Re: Is postgres able to share sorts required by common partition window functions?

[Sebastien Arod <sebastien.arod@xxxxxxxxx>]

Hi Michael,

I simplified the real query before posting it here and I now realize that I oversimplified things.

Unfortunately the real query cannot be re-written with a group by.

Some of the window functions are more complex with order by clause using complex expressions involving multiple columns.

The following example would be more realistic:

select distinct
  c1,
  first_value(c2) OVER (PARTITION BY c1 order by c2, c4) AS c2,
  first_value(c3) OVER (PARTITION BY c1 order by coalesce(c4, '000'), c3) AS c3

from  
  t;

On Mon, Jul 6, 2020 at 9:55 PM Michael Lewis <mlewis@xxxxxxxxxxx> wrote:

Does this give the same result and do the optimization you want?

select
  c1,
  min(c2) AS c2,
  min(c3) AS c3,
  min(c4) AS c4
from  
  t

group by

  c1;