Re: Utilizing multiple cores for one query

On Sat, 1 Dec 2007, Jonah H. Harris wrote:
> I believe the threads you're talking about were related to scanning,
> not parallel query.  Though, when Qingqing and I were discussing
> parallel query a little over a year ago, I do seem to recall several
> uninformed opinions stating that sequential scans were the only thing
> it could be useful for.

I would imagine sorting a huge set of results would benefit from
multi-threading, because it can be split up into separate tasks. Heck,
Postgres *already* splits sorting up into multiple chunks when the results
to sort are bigger than fit in memory.

This would benefit a lot of multi-table joins, because being able to sort
a table faster would enable merge joins to be used at lower cost. That's
particularly valuable when you're doing a large summary multi-table join
that uses most of the database contents.

Matthew

--
Beware of bugs in the above code; I have only proved it correct, not
tried it.                                               --Donald Knuth