From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: ruleutils vs. empty targetlists |
Date: | 2013-12-04 14:01:32 |
Message-ID: | 20131204140132.GM5158@eldon.alvh.no-ip.org |
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Lists: | pgsql-hackers |
Tom Lane escribió:
> What I'm thinking about this today is that really the *right* solution
> is to allow syntactically-empty SELECT lists; once we've bought into the
> notion of zero-column tables, the notion that you can't have an empty
> select list is just fundamentally at odds with that. And since you can
> already have semantically-empty SELECT lists, this should in theory not
> create much risk of new bugs. If we did that, the existing ruleutils
> code is just fine, as are any existing dump files containing this sort
> of query.
Wow, as strange-sounding as that is, you're probably correct.
This might probably be seen as a deviation from the standard, but then
so are zero-column tables. Of course, syntactically-empty select lists
would also work with (standard-conforming) tables containing columns,
but it's hard to see that that would be a problem in practice.
> That change might still be thought too aggressive for a back-patch,
> though. Comments?
Well, no correct query will start failing due to this change; the only
visible change would be queries that previously throw errors would start
working. It's hard to see that as a backward-incompatibility.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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