Horton

Re: [BUG] Remove self joins causes 'variable not found in subplan target lists' error

Maksim Milyutin <maksim.milyutin@tantorlabs.ru>

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From: Maksim Milyutin <maksim.milyutin@tantorlabs.ru>
To: Tom Lane <tgl@sss.pgh.pa.us>, Richard Guo <guofenglinux@gmail.com>
Cc: Sergey Soloviev <sergey.soloviev@tantorlabs.ru>, pgsql-hackers@lists.postgresql.org
Date: 2025-08-26T20:04:20Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix semijoin unique-ification for child relations

  2. Fix "variable not found in subplan target lists" in semijoin de-duplication.

  3. Recalculate where-needed data accurately after a join removal.

On 8/26/25 20:26, Tom Lane wrote:

> Richard Guo <guofenglinux@gmail.com> writes:
>
>> We could then use this function to remove expressions that are known
>> constant from semi_rhs_exprs.  And if we find that all expressions
>> in semi_rhs_exprs are known constant (the second loose end you
>> mentioned), we can give up building unique paths and fall back to a
>> traditional JOIN_SEMI.
> Yeah, I was thinking we could just use the paths of the existing
> rel, but really this case means that we'd need to de-dup down
> to a single row.  We could maybe do something involving plastering
> LIMIT 1 on top of each input path

Unique node over incoming empty rows seems to act as LIMIT 1, in 
particular, it breaks subplan execution after extracting the first row. 
Then I see v3 patch covers this case perfectly.


-- 
Best regard,
Maksim Milyutin