Horton

Re: pg_upgrade failed if view contain natural left join condition

Tom Lane <tgl@sss.pgh.pa.us>

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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>
Date: 2017-07-20T16:14:06Z
Lists: pgsql-hackers 
"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

Commits

  1. Doc: clarify description of degenerate NATURAL joins.

  2. Fix dumping of outer joins with empty qual lists.