Josh Berkus <josh@agliodbs.com> writes:
> Basically reading a large table off disk does this:
> read some table while not processing
> process in cpu while not reading
> read some more table while not processing
> process some more in cpu while not reading
> etc.
> resulting in an I/O througput graph that looks like:
> * * *
> * * * * * *
> * * * * * *
> * * * *
Interesting ...
> The really annoying part about this, for me personally, is that the peaks
> are significantly faster than comparable commercial DBMSes ... but our
> average is far less. So even on a single seq scan, parallel query
> execution would make a significant difference in performance, possibly as
> much as +75% on seq scans of large tables.
... but I'm failing to follow where it says that parallel processing
will fix that. All I can foresee in that direction is extra data
transfer costs, bought at the price of portability and locking headaches.
regards, tom lane
---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?
http://www.postgresql.org/docs/faq
