Re:

I am curious - I wasn't aware that postgresql supported partitioned tables,
Could someone point me to the docs on this.

Thanks,

Alex Turner
NetEconomist

On Thu, 20 Jan 2005 09:26:03 -0500, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> * Matt Casters (Matt(dot)Casters(at)advalvas(dot)be) wrote:
> > I have the go ahead of a customer to do some testing on Postgresql in a couple of weeks as a
> > replacement for Oracle.
> > The reason for the test is that the number of users of the warehouse is going to increase and this
> > will have a serious impact on licencing costs. (I bet that sounds familiar)
>
> Rather familiar, yes... :)
>
> > We're running a medium sized data warehouse on a Solaris box (4CPU, 8Gb RAM) on Oracle.
> > Basically we have 2 large fact tables to deal with: one going for 400M rows, the other will be
> > hitting 1B rows soon.
> > (around 250Gb of data)
>
> Quite a bit of data. There's one big thing to note here I think-
> Postgres will not take advantage of multiple CPUs for a given query,
> Oracle will. So, it depends on your workload as to how that may impact
> you. Situations where this will be unlikely to affect you:
>
> Your main bottle-neck is IO/disk and not CPU.
> You run multiple queries in parallel frequently.
> There are other processes on the system which chew up CPU time anyway.
>
> Situations where you're likely to be affected would be:
>
> You periodically run one big query.
> You run a set of queries in sequential order.
>
> > My questions to the list are: has this sort of thing been attempted before? If so, what where the
> > performance results compared to Oracle?
>
> I'm pretty sure it's been attempted before but unfortunately I don't
> have any numbers on it myself. My data sets aren't that large (couple
> million rows) but I've found PostgreSQL at least as fast as Oracle for
> what we do, and much easier to work with.
>
> > I've been reading up on partitioned tabes on pgsql, will the performance benefit will be
> > comparable to Oracle partitioned tables?
>
> In this case I would think so, except that PostgreSQL still won't use
> multiple CPUs for a given query, even against partitioned tables, aiui.
>
> > What are the gotchas?
>
> See above? :) Other issues are things having to do w/ your specific
> SQL- Oracle's old join syntax isn't supported by PostgreSQL (what is it,
> something like select x,y from a,b where x=%y; to do a right-join,
> iirc).
>
> > Should I be testing on 8 or the 7 version?
>
> Now that 8.0 is out I'd say probably test with that and just watch for
> 8.0.x releases before you go production, if you have time before you
> have to go into production with the new solution (sounds like you do-
> changing databases takes time anyway).
>
> > Thanks in advance for any help you may have, I'll do my best to keep pgsql-performance up to date
> > on the results.
>
> Hope that helps. Others on here will correct me if I misspoke. :)
>
> Stephen
>
>
>