Re: Hardware upgrade for a high-traffic database

[snip]
>
> One question I do have though - you specifically mentioned NOW() as
> something to watch out for, in that it's mutable.  We typically use COUNT()
> as a subselect to retrieve the number of associated rows to the current
> query.  Additionally, we use NOW a lot, primarily to detect the status of a
> date, i.e.:
>
> SELECT id FROM subscriptions WHERE userid = 11111 AND timeend > NOW();
>
> Is there a better way to do this?  I was under the impression that NOW() was
> pretty harmless, just to return a current timestamp.
>
NOW() will trigger unnessecary sequence scans.  As it is unknown with prepared
query and function when the statement is run, the planner plans the query with
now as a variable.  This can push the planner to a seq scan over and index scan.
I have seen this time and time again.

You can create your own immutable now, but don't use it in functions or prepared queries
or you will get wrong results.

> Based on feedback, I'm looking at a minor upgrade of our RAID controller to
> a 3ware 9000 series (SATA with cache, battery backup optional), and
> re-configuring it for RAID 10.  It's a damn cheap upgrade at around $350 and
> an hour of downtime, so I figure that it's worth it for us to give it a
> shot.
>
> Thanks,
>
> Jason

Russell Smith