From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg_upgrade failed if view contain natural left join condition |
Date: | 2017-07-20 15:57:37 |
Message-ID: | CAKFQuwb+mYszQhDS9f_dqRrk1=Pe-S6D=XMkAXcDf4ykKPmgKQ@mail.gmail.com |
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On Thu, Jul 20, 2017 at 6:53 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> tushar <tushar(dot)ahuja(at)enterprisedb(dot)com> writes:
> > postgres=# create table t(n int);
> > CREATE TABLE
> > postgres=# create table t1(a int);
> > CREATE TABLE
> > postgres=# create view ttt1 as SELECT e.n FROM t e NATURAL LEFT JOIN t1
> d;
> > CREATE VIEW
>
> You realize of course that that's a pretty useless join definition.
> Still, yes, we do need to reverse-list the view with correct syntax.
> Probably t LEFT JOIN t1 ON TRUE would do it.
>
Per the docs:
"If there are no common column names, NATURAL behaves like CROSS JOIN."
I'm being a bit pedantic here but since NATURAL is a replacement for
"ON/USING" it would seem more consistent to describe it, when no matching
columns are found, as "behaves like specifying ON TRUE" instead. Maybe
"behaves like specifying ON TRUE, causing a CROSS JOIN to occur instead."
I find it a bit strange, though not surprising, that it doesn't devolve to
"ON FALSE".
David J.
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