Re:

On Tue, Jun 27, 2017 at 11:47 PM, Yevhenii Kurtov <yevhenii(dot)kurtov(at)gmail(dot)com
> wrote:

> Hello,
>
> We have a query that is run almost each second and it's very important to
> squeeze every other ms out of it. The query is:
>
> SELECT c0."id" FROM "campaign_jobs" AS c0
> WHERE (((c0."status" = $1) AND NOT (c0."id" = ANY($2))))
> OR ((c0."status" = $3) AND (c0."failed_at" > $4))
> OR ((c0."status" = $5) AND (c0."started_at" < $6))
> ORDER BY c0."priority" DESC, c0."times_failed"
> LIMIT $7
> FOR UPDATE SKIP LOCKED
>
>

>
> I see that query still went through the Seq Scan instead of Index Scan. Is
> it due to poorly crafted index or because of query structure? Is it
> possible to make this query faster?
>

An index on (priority desc, times_failed) should speed this up massively.
Might want to include status at the end as well. However, your example data
is not terribly realistic.

What version of PostgreSQL are you using?

Cheers,

Jeff