Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Kevin Grittner <kgrittn(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)
Date: 2016-09-02 14:34:54
Message-ID: 10498.1472826894@sss.pgh.pa.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

Andres Freund <andres(at)anarazel(dot)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

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Kevin Grittner 2016-09-02 14:41:28 Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)
Previous Message Andres Freund 2016-09-02 14:25:16 Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)