Re: Intersect/Union X AND/OR

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.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +