Re: logical column ordering

Tomas Vondra wrote:
> On 26.2.2015 23:42, Kevin Grittner wrote:

> > One use case is to be able to suppress default display of columns
> > that are used for internal purposes. For example, incremental
> > maintenance of materialized views will require storing a "count(t)"
> > column, and sometimes state information for aggregate columns, in
> > addition to what the users explicitly request. At the developers'
> > meeting there was discussion of whether and how to avoid displaying
> > these by default, and it was felt that when we have this logical
> > column ordering it would be good to have a way tosuppress default
> > display. Perhaps this could be as simple as a special value for
> > logical position.
>
> I don't see how hiding columns is related to this patch at all. That's
> completely unrelated thing, and it certainly is not part of this patch.

It's not directly related to the patch, but I think the intent is that
once we have this patch it will be possible to apply other
transformations, such as having columns that are effectively hidden --
consider for example the idea that attlognum be set to a negative
number. (For instance, consider the idea that system columns may all
have -1 as attlognum, which would just be an indicator that they are
never present in logical column expansion. That makes sense to me; what
reason do we have to keep them using the current attnums they have?)

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Álvaro Herrera http://www.2ndQuadrant.com/
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