From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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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 |
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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
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