From: | Moritz Onken <onken(at)houseofdesign(dot)de> |
---|---|
To: | |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Slow query with a lot of data |
Date: | 2008-08-18 15:49:38 |
Message-ID: | 0BFF9855-F1FA-4A83-B8B2-622D7CE69F77@houseofdesign.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
>>
>
> Well, you're getting the database to read the entire contents of the
> domain_categories table in order. That's 12 million rows - a fair
> amount of work.
>
> You may find that removing the "user = 1337" constraint doesn't make
> the query much slower - that's where you get a big win by clustering
> on domain. You might also want to cluster the results table on domain.
Running the query for more than one user is indeed not much slower.
That's what I need. I'm clustering the results table on domain right
now. But why is this better than clustering it on "user"?
>
>
> If you want the results for just one user, it would be very helpful
> to have a user column on the domain_categories table, and an index
> on that column. However, that will slow down the query for all users
> a little.
A row in domain_categories can belong to more than one user. But I
don't need to run this query for only one user anyway.
Thanks so far,
From | Date | Subject | |
---|---|---|---|
Next Message | Matthew Wakeling | 2008-08-18 16:05:11 | Re: Slow query with a lot of data |
Previous Message | Mark Wong | 2008-08-18 15:33:44 | Re: file system and raid performance |