On Fri, Dec 2, 2011 at 1:49 PM, Bruce Momjian <bruce@xxxxxxxxxx> wrote: > Thiago Godoi wrote: >> Hi all, >> >> I found this presentation from B. Momjian: >> >> http://momjian.us/main/writings/pgsql/performance.pdf >> >> I'm interested in what he said about " Intersect/Union X AND/OR " , Can I >> find a transcription or a video of this presentation? Can anyone explain it >> to me? > > Well, there is a recording of the webcast on the EnterpriseDB web site, > but I am afraid they only allow viewing of 3+ hour webcasts by > EnterpriseDB customers. > > The idea is that a query that uses an OR can be rewritten as two SELECTs > with a UNION between them. I have seen rare cases where this is a win, > so I mentioned it in that talk. Intersection is similarly possible for > AND in WHERE clauses. I've seen this as well. Also boolean set EXCEPT is useful as well in the occasional oddball case. merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
