Re: [GENERAL] Long update query ? (also Re: [GENERAL] CNF vs. DNF)

Taral <taral@mail.utexas.edu>

From: "Taral" <taral@mail.utexas.edu>
To: "Bruce Momjian" <maillist@candle.pha.pa.us>
Cc: <pgsql-general@postgreSQL.org>
Date: 1998-10-01T23:45:33Z
Lists: pgsql-hackers, pgsql-general
> > Wouldn't disjunctive normal form be better, since it can be
> implemented as
> > the simple union of a set of small queries?
>
> Please tell us more.

Well, I don't know how the backend processes queries, but one can imagine
this scenario (for DNF):

1) Analyze query and set up columns in result table
2) Rewrite query into DNF
3) Split query into subqueries
4) For each subquery:
  a) Process query
  b) Append matching tuples to result table
5) Do any post-processing (ORDER BY, etc.)
6) Return result

How is the processing currently done (with CNF)?

Taral