On Tue, Jul 12, 2016 at 10:23:24AM +0200, Bjørn T Johansen wrote: > I am trying to move a small system from Oracle to PostgreSQL and > I have come upon a sql that runs really slow compared to on the Oracle > database and I am not able to interpret why this is slow.
I loaded your explain analyze to https://explain.depesz.com/, as: https://explain.depesz.com/s/iXK as you can see there, the problem is that you made 280 thousand checks for "sed_uttak y", which seems to be related to this part: > Select a.status, a.plass, a.navn, a.avlsnr, > date_part('day',(now() - s.dato)) dato_diff, v.tekst, > COALESCE(a.avlsverdi,0) > From sed_uttak s, sem_avlsverdi a, semin_vare v > where a.aktiv = 1 > And s.dato = (Select Max(y.dato) > From sed_uttak y > Where y.avlsnr = s.avlsnr) from what I understand, you're doing it to work on newest record from sed_uttak, for each avlsnr. What is rowcount in the table, and how many different avlsnr are there? You might want to do something like: with s as ( select distinct on (avlsnr) * from sed_uttak order by avlsnr desc, dato desc ) and then use "s" instead of set_uttak, and get rid of the s.dato = (select max....) checks. Best regards, depesz -- The best thing about modern society is how easy it is to avoid contact with it. http://depesz.com/ -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
