Re: Distinct performance dropped by multiple times in v16

[Greg Sabino Mullane <htamfids@xxxxxxxxx>]

On Mon, Jun 10, 2024 at 3:32 AM Vitaliy Litovskiy <vitaliy.litovskiy@xxxxxxxxx> wrote:

1. query runs for 4-5 seconds on v16 and less than a second on v15

Yeah, that's a big regression.  Seeing the actual EXPLAIN ANALYZE output for both systems would be very helpful to us. Also nice to see the plan if you do a 

SET enable_incremental_sort=0;

before running the query

I wonder if materializing things might help, something like

with

  x as (select id, unnest(string_to_array(emp,';')) as token, refdate from terr),

  y as (select id, unnest(string_to_array(emp,';')) as token from employee)

select distinct x.id, y.id, refdate from x join y using (token);

(renamed to avoid all those mixed-case quoting)

Cheers,

Greg