Thread: Query Optimizer + Parallel Operators

Everybody,

I'm interested in the query optimizer of PostgreSQL DB. Where could I
find useful documentation or could you send me a pointer in the source code?

What kind of parallelism does PostgreSQL use for operators, like
selection or join?

Thank you
- felix

Felix,

> I'm interested in the query optimizer of PostgreSQL DB. Where could I
> find useful documentation or could you send me a pointer in the source code?
> 
> What kind of parallelism does PostgreSQL use for operators, like
> selection or join?

Normally we're very helpful with this kind of information ... it's all
public after all ... but I have to say that the domain you're e-mailing
from makes it a little hard to give you a direct answer.

Could you maybe give us a little information about what you want this
information for?

--                                  -- Josh Berkus                                    PostgreSQL Experts Inc.
                        http://www.pgexperts.com
 

On 26.01.2011 16:46, Felix Schmidt @ Oracle wrote:
> Everybody,
>
> I'm interested in the query optimizer of PostgreSQL DB. Where could I
> find useful documentation or could you send me a pointer in the source code?

The relevant source code is in src/backend/optimizer directory. If you 
google around, you'll find introductory presentations, but I can't 
recommend any particular one.

> What kind of parallelism does PostgreSQL use for operators, like
> selection or join?

The short answer is "none". Each PostgreSQL backend is a one 
single-threaded process, one query will only utilize one CPU 
(http://wiki.postgresql.org/wiki/FAQ#How_does_PostgreSQL_use_CPU_resources.3F).

If you search the archives, you'll find discussion on how it might one 
day be improved, but nothing concrete has been done.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com