Re: PostgreSQL OR performance

2008/11/7 Richard Huxton <dev(at)archonet(dot)com>

> But it's this materialize that's taking the biggest piece of the time.
>
> > " -> Materialize (cost=469981.13..498937.42 rows=2316503 width=30)
> > (actual time=15915.639..391938.338 rows=242752539 loops=1)"
>
> 15.9 seconds to 391.9 seconds. That's half your time right there. The
> fact that it's ending up with 242 million rows isn't promising - are you
> sure the query is doing what you think it is?

I am not. I can't see how materialize can multiply number of rows it gets
from sort by 100.

>
> > " -> Sort (cost=469981.13..475772.39 rows=2316503 width=30)
> (actual
> > time=15915.599..19920.912 rows=2316503 loops=1)"
> > " Sort Key: production.company.run_id"
> > " Sort Method: external merge Disk: 104896kB"
>
> By constrast, this on-disk sort of 104MB is comparatively fast.
>