Re: BUG #18284: Filter in left lateral join not respected

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От Richard Guo
Тема Re: BUG #18284: Filter in left lateral join not respected
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Msg-id CAMbWs48r0MMEQoG8NWm7MTjDb_fbvCGEoYt_XpurDbrvuB5ZtA@mail.gmail.com
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Ответ на Re: BUG #18284: Filter in left lateral join not respected  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: BUG #18284: Filter in left lateral join not respected  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Fri, Jan 12, 2024 at 1:30 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Huh.  It looks like the oversight is actually even more ancient than
that, dating clear back to 9e7e29c75 of 2013-08-17.  That commit
recognized that lateral-reference Vars had to be wrapped in
PlaceHolderVars during subquery pullup, but failed to make the same
conclusion for PlaceHolderVars. 

Exactly.
 
Somehow that didn't cause any visible
problems before 4be058fe9, or more likely we just didn't get any
relevant trouble reports. 

I believe it should be the latter case.  It's not hard to show this
problem before 4be058fe9.

create table t (a int);
insert into t values (1);

# select t2a_lateral from t t1
    left join (select coalesce(t2.a) as a from t t2) s on true
    left join lateral (select s.a as t2a_lateral from t t3) ss on false;
 t2a_lateral
-------------
           1
(1 row)

The t2a_lateral is supposed to be NULL not 1.

Thanks
Richard

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