From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Kevin Grittner <kgrittn@gmail.com>, Robert Haas <robertmhaas@gmail.com>,
        "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in
 targetlist handling)
In-reply-to: <20160902142516.4oarwuvqoanyoezx@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Fri, 02 Sep 2016 07:25:16 -0700"
Date: Fri, 02 Sep 2016 10:34:54 -0400
Message-ID: <10498.1472826894@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Andres Freund <andres@anarazel.de> writes:
> On 2016-09-02 10:20:42 -0400, Tom Lane wrote:
>> ... ISTM all we
>> need is that the SRF be on the inside of the join, which is automatic
>> if it's LATERAL.

> Right. But there's nothing to force a lateral reference to be there
> intrinsically. I've added a "fake" lateral reference to the ROWS FROM
> RTE to the subquery, when there's none otherwise, but that's not
> entirely pretty.

Hm, do you get cases like this right:

	select generate_series(1, t1.a) from t1, t2;

That would result in a lateral ref from the SRF RTE to t1, but you really
need to treat it as laterally dependent on the join of t1/t2 in order to
preserve the old semantics.  That is, you need to be laterally dependent
on the whole FROM clause regardless of which variable references appear.

			regards, tom lane


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