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Re: logical column ordering

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Andres Freund <andres(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: logical column ordering
Date: 2015-04-14 21:43:54
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Lists: pgsql-hackers
On Tue, Apr 14, 2015 at 2:38 PM, Alvaro Herrera
<alvherre(at)2ndquadrant(dot)com> wrote:
> As I said, I'm still writing the first pieces of this so I'm not sure
> what other ramifications it will have.  If there are any thoughts, I
> would appreciate them.  (Particularly useful input on whether it is
> acceptable to omit lognums/physnums from _outRangeTblEntry.)

I think the general rule is that an RTE should not contain any
structure information about the underlying relation that can
potentially change: the OID is OK because it's immutable for any given
relation.  The relkind is not quite immutable because you can create a
_SELECT rule on a table and turn it into a view; I'm not sure how we
handle that, but it's a fairly minor exception anyhow.  Everything
else in the RTE, with the new and perhaps-unfortunate exception of
security quals, is stuff derived from what's in the query, not the
table.  I think it would be good for this to work the same way: the
structural information about the table should be found in the
relcache, not the RTE.

Robert Haas
The Enterprise PostgreSQL Company

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