Re: BUG #18187: Unexpected error: "variable not found in subplan target lists" triggered by JOIN

On 20/11/2023 15:49, Richard Guo wrote:
>     I'm wondering if we can relax this restriction because it seems to me
>     that a PHV evaluated/needed at or below the self join should not have
>     problem if we remove the self join.
> 
> 
> After some more thought, I think PHVs should not impose any constraints
> on removing self joins.  If the removed rel is contained in the relids
> that a PHV is evaluated/needed at or laterally references, it can just
> be replaced with the rel that is kept.
> 
> Attached is a patch to remove such constraints.  Any comments or
> feedback are welcome.

Carrying out excavations, I found that it was Teodor Sigaev who added 
this limitation in v.20 of the patch in an earlier stage of the development.
I also had analyzed this part of code and came to the conclusion that it 
doesn't needed. Only a paranoid approach and the absence of an 
alternative opinion are the reasons why this code is still exists.
Your patch is ok.
I think the comment, 'PHVs should not impose ...' looks redundant. It 
may be enough to have it in the commit comment.

-- 
regards,
Andrei Lepikhov
Postgres Professional