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From Dave Birdsall <dave.birds...@esgyn.com>
Subject RE: question on normalization
Date Mon, 14 Dec 2015 21:36:01 GMT
I don't know for sure, but I'll speculate that histogram estimation and
RangeSpec processing in the compiler like to think in terms of intervals.

-----Original Message-----
From: Hans Zeller [mailto:hans.zeller@esgyn.com]
Sent: Monday, December 14, 2015 1:35 PM
To: dev <dev@trafodion.incubator.apache.org>
Subject: Re: question on normalization

Hi Eric, yes, the logic may be unconditional, since at the time when we do
these transformations, we don't know yet whether the predicate is used in an
alternate index or not, and since the overhead of the extra predicate is
probably small.

Hans

On Mon, Dec 14, 2015 at 1:31 PM, Eric Owhadi <eric.owhadi@esgyn.com> wrote:

> Sorry should have said that "an" is not a key column. So any logic
> around MDAM should not apply.
> Eric
>
> -----Original Message-----
> From: Hans Zeller [mailto:hans.zeller@esgyn.com]
> Sent: Monday, December 14, 2015 3:30 PM
> To: dev <dev@trafodion.incubator.apache.org>
> Subject: Re: question on normalization
>
> Hi Eric, this is probably to get usable key predicates. "an <> 1" is
> not a key range we could use, but "an < 1" and "an > 1" make two
> disjuncts for an MDAM scan.
>
> Hans
>
> On Mon, Dec 14, 2015 at 1:25 PM, Eric Owhadi <eric.owhadi@esgyn.com>
> wrote:
>
> > I am implementing predicate push down enhancement. doing so, I found
> > something weird.
> >
> > If I do select an from t132 where an != 1
> >
> > The normalized predicate is ((an < 1) or <an >1))
> >
> > I would have expected a simple an <> 1
> >
> > There is probably a reason being this? But what is it?
> >
> > Thanks in advance for the help,
> > Eric
> >
>

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