| From: | "Taral" <taral(at)mail(dot)utexas(dot)edu> | 
|---|---|
| To: | "Bruce Momjian" <maillist(at)candle(dot)pha(dot)pa(dot)us> | 
| Cc: | <pgsql-general(at)postgreSQL(dot)org> | 
| Subject: | Re: [GENERAL] Long update query ? (also Re: [GENERAL] CNF vs. DNF) | 
| Date: | 1998-10-01 23:45:33 | 
| Message-ID: | 000001bded95$94a20cc0$3b291f0a@taral | 
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| Thread: | |
| Lists: | pgsql-general pgsql-hackers | 
> > 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
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