From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: tushar <tushar.ahuja@enterprisedb.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: pg_upgrade failed if view contain natural left join condition
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Thu, 20 Jul 2017 08:57:37 -0700"
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Date: Thu, 20 Jul 2017 12:14:06 -0400
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> 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.

Yeah, the analogy to CROSS JOIN falls down if it's an outer join.
I'll go fix that.

> I find it a bit strange, though not surprising, that it doesn't devolve to
> "ON FALSE".

No, it's normal that an AND of no conditions degenerates to TRUE.
It's like omitting a WHERE clause.

			regards, tom lane


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