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From Jacques Nadeau <jacq...@apache.org>
Subject Re: Implicit Columns: Only there when you ask for them...
Date Tue, 18 Apr 2017 15:39:34 GMT
James, thanks for the reminder on EXTENDS. And Julian, thanks for the
reminder of the _MAP, that must have been what I was remembering. I'm
actually looking for something slightly different:

I want a column to exists for validation when explicitly requested but be
excluded from star expansion. Any other ideas on how to handle this? Think
ROWNUM in Oracle. I guess they call it a pseudocolumn.

On Mon, Apr 17, 2017 at 11:49 PM, Julian Hyde <jhyde@apache.org> wrote:

> There’s also the “_MAP” column returned by the MongoDB and Elasticsearch
> adapters. It contains a (key, value) pair for the top-level fields of each
> row. It DOES appear in SELECT *.
>
> We had the idea of rewriting
>
>   SELECT empno FROM Emp
>
> to
>
>   SELECT _MAP[‘empno’] FROM Emp
>
> if Emp had a particular row type but I don’t think we ever did it.
>
> Julian
>
>
>
>
> > On Apr 17, 2017, at 7:27 PM, James Taylor <jamestaylor@apache.org>
> wrote:
> >
> > Hey Jacques,
> > The EXTENDS (col1 type, col2 type)  keyword can be used for this (and the
> > EXTENDS keyword is optional). Something like this in Phoenix:
> >
> > SELECT foo FROM bar (my_col VARCHAR) WHERE my_col = 'bas'
> >
> > Phoenix uses this for dynamic column support.
> >
> > Thanks,
> > James
> >
> > On Mon, Apr 17, 2017 at 7:17 PM, Jacques Nadeau <jacques@apache.org>
> wrote:
> >
> >> Hey All,
> >>
> >> I remember there being a syntax in Calcite that allowed one to define an
> >> _EXTRA column or columns that could be referenced in Calcite but
> wouldn't
> >> be included in a select *. If I recall, the Splunk adapter used this at
> one
> >> point. Does this actually exist or have I lost my mind. I can't seem to
> >> find a reference to this anywhere.
> >>
> >> thanks!
> >>
>
>

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