Re: Deleting more efficiently from large partitions

What version of PG?
What does EXPLAIN show?

Sent from my iPad

> On Jun 15, 2020, at 9:39 PM, Wells Oliver <wells(dot)oliver(at)gmail(dot)com> wrote:
>
> Hi all. I have a partitioned table (by month from a date column), where each partition contains something like 400m rows.
>
> Each partition is defined by a PK with a uuid and date field (the parent table is partitioned by range on the date), and two other columns.
>
> In doing a delete for a specific date, e.g. DELETE FROM t WHERE date = '2019-09-01' AND uuid IN (SELECT uuid FROM temptable), it runs very efficiently.
>
> I am trying to write a processing script that deletes for potentially multiple dates & uuid values, and it just takes hours, trying:
>
> DELETE FROM t WHERE date = (SELECT DISTINCT date from temp) AND uuid IN (select uuid from tempuuds) -- no go, hours.
>
> Tried USING, e.g. DELETE FROM t USING temp WHERE t.date = temp.date AND t.uuid = temp.uuid -- no go, hours.
>
> I just can't delete from this table without an explicit date and a set of uuids using a WHERE IN approach, but I need to.I was thinking of making a plpgsql function or something that loops through dates and makes a more explicit DELETE statement, but I'm thinking there must be some better way using indexing or something.
>
> Appreciate any tips.
>
>
> --
> Wells Oliver
> wells(dot)oliver(at)gmail(dot)com