From: | "Vadim B(dot) Mikheev" <vadim(at)sable(dot)krasnoyarsk(dot)su> |
---|---|
To: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | hackers(at)postgreSQL(dot)org |
Subject: | Re: [PATCHES] Re: [HACKERS] Query->hasSubLinks is always FALSE... |
Date: | 1998-02-09 17:56:06 |
Message-ID: | 34DF4336.B17928D5@sable.krasnoyarsk.su |
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Lists: | pgsql-hackers |
Bruce Momjian wrote:
>
> >
> > > me about two or three days to do the parser and rewrite for sublinks.
> > > How many coding days is the rest taking? I am curious.
> >
> > All was near ready Feb 6, but ... I got problems from canonification
> > routines in optimizer: 'where A AND B OR C ' becomes 'where (A OR C) AND (B OR C)'
> > and if C is subselect then ... C has to be processed twice (sometime) ...
> > I remember your question about handling 'A AND (B OR SubSelect)' - unfortunately,
> > I didn't see problems here (actually, there is no problem with this
> > conjunctive normal form :), but there are troubles in common case.
> >
> > Ideas ?
> >
> > For the moment I could leave this un-optimized, with possibility
> > of double subselect processing...
>
> I would leave it for later. We already have an optimizer explosion
> problem when we have lots of OR's so at some point we may have to
> revisit the cnf-ify process anyway. Commerical Ingres has or had the
> same problem.
Ok, follow this way...
Vadim
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