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