From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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 15:29:37 |
Message-ID: | 20160902152937.r32ao3neffdn4hpm@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2016-09-02 10:34:54 -0400, Tom Lane wrote:
> 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.
Yes - as the original query is moved into a subquery, the lateral
dependency I force-add simply is to the entire subquery atm (as a
wholerow var).
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