Re: PostgreSQL process architecture question.

On Wed, 2008-09-10 at 00:02 -0600, Scott Marlowe wrote:

> Unless you have either a small data set or a very powerful RAID array,
> most the time you won't be CPU bound anyway. But it would be nice to
> see some work come out to parallelize some of the work done in the
> back end.

I would have agreed with this several years ago, but many folks now buy
enough RAM to reduce the impact of IO. We're routinely CPU-bound on
small queries, and even on some large ones, on a 32GB / 16-core Opteron
box that serves a ~200GB database (on disk tables+indexes).

Does anyone know of research/references on query optimizers that include
parallelization as part of the cost estimate? I can envision how
PostgreSQL might parallelize a query plan that was optimized with an
assumption of one core. However, I wonder whether cpu and io costs are
sufficient for efficient parallel query optimization -- presumably
contention for memory (for parallel sorts, say) becomes critical.

-Reece

--
Reece Hart, http://harts.net/reece/, GPG:0x25EC91A0