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* does postgresql execute unions in parallel?
@ 2003-09-25 17:04 teknokrat <teknokrat@yahoo.com>
0 siblings, 2 replies; 4+ messages in thread
From: teknokrat @ 2003-09-25 17:04 UTC (permalink / raw)
To: pgsql-sql
If I have several selects joined with unions does postgresql execute the
concurrently or not?
thanks
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: does postgresql execute unions in parallel?
@ 2003-09-26 19:58 Gaetano Mendola <mendola@bigfoot.com>
parent: teknokrat <teknokrat@yahoo.com>
1 sibling, 1 reply; 4+ messages in thread
From: Gaetano Mendola @ 2003-09-26 19:58 UTC (permalink / raw)
To: pgsql-sql; +Cc: teknokrat@yahoo.com
teknokrat wrote:
> If I have several selects joined with unions does postgresql execute the
> concurrently or not?
nope.
Regards
Gaetan Mendola
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: does postgresql execute unions in parallel?
@ 2003-09-26 20:28 Christopher Browne <cbbrowne@acm.org>
parent: Gaetano Mendola <mendola@bigfoot.com>
0 siblings, 0 replies; 4+ messages in thread
From: Christopher Browne @ 2003-09-26 20:28 UTC (permalink / raw)
To: pgsql-sql
mendola@bigfoot.com (Gaetano Mendola) writes:
> teknokrat wrote:
>> If I have several selects joined with unions does postgresql
>> execute the concurrently or not?
>
> nope.
I was talking with Jan about that very idea yesterday; this would seem
to be the place where PostgreSQL might take some (possibly even nearly
magical :-)) benefit from threading.
The usual way that people expect to use threading is for each
connection to have a thread.
If, instead, every _join_ had a thread, that would allow producers of
data to look for their data quasi-independently, passing result sets
upwards towards the return set to whatever thread was waiting to
consume the data.
This would allow one complex query to take over a whole horde of
processors :-).
The "magic" part would be if the system decided, "The SEQ SCAN on the
table I'm looking at is a big one; let's split it into 4 chunks, doing
a virtual UNION ALL, and thereby filter bits of it in parallel on 4
CPUs." That would provide many of the benefits Informix claimed from
"fragmentation" without having to fragment the table :-).
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: does postgresql execute unions in parallel?
@ 2003-09-29 17:54 Bruce Momjian <pgman@candle.pha.pa.us>
parent: teknokrat <teknokrat@yahoo.com>
1 sibling, 0 replies; 4+ messages in thread
From: Bruce Momjian @ 2003-09-29 17:54 UTC (permalink / raw)
To: teknokrat@yahoo.com; +Cc: pgsql-sql
teknokrat wrote:
> If I have several selects joined with unions does postgresql execute the
> concurrently or not?
No.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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-- links below jump to the message on this page --
2003-09-25 17:04 does postgresql execute unions in parallel? teknokrat <teknokrat@yahoo.com>
2003-09-26 19:58 ` Gaetano Mendola <mendola@bigfoot.com>
2003-09-26 20:28 ` Christopher Browne <cbbrowne@acm.org>
2003-09-29 17:54 ` Bruce Momjian <pgman@candle.pha.pa.us>
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