[EMAIL PROTECTED] (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 :-). -- If this was helpful, <http://svcs.affero.net/rm.php?r=cbbrowne> rate me http://www3.sympatico.ca/cbbrowne/lsf.html Rules of the Evil Overlord #187. "I will not hold lavish banquets in the middle of a famine. The good PR among the guests doesn't make up for the bad PR among the masses." <http://www.eviloverlord.com/> ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
