Re: PlaceholderVars and join removal with appendrel parents

Hi Tender,

thanks for having a look here again.

On 2026-07-13 3:44 PM, Tender Wang wrote:
> Arne Roland <arne(dot)roland(at)malkut(dot)net> 于2026年7月13日周一 18:24写道：
>> Hi Richard,
>>
>> thank you for your great work with the optimizer!
>>
>> I just stumbled and by accident landed on your commit 9a60f295bcb (and
>> then looked up the discussion
>> https://www.postgresql.org/message-id/flat/CALzhyqwryL2QywgO03VQr_237Sq3MEVgTTT2_A9G3nGT5-SRZg%40mail.gmail.com)
>> I am under the impression we need to extend the same fix for or clauses
>> descending into the orclause sub-RestrictInfos.
>>
>> This is the simplified minimal test case, that is failing for me:
>>
>> CREATE TABLE a (id int PRIMARY KEY, b_id int);
>> CREATE TABLE uniq (id int PRIMARY KEY);
>> CREATE TABLE parted_b (id int PRIMARY KEY) PARTITION BY RANGE (id);
>> CREATE TABLE parted_b1 PARTITION OF parted_b FOR VALUES FROM (0) TO (10);
>>
>> SELECT 1 FROM a, (SELECT t1.id FROM parted_b t1 LEFT JOIN uniq t2 ON
>> t1.id = t2.id) s
>> WHERE (s.id = 1 AND a.id = 2) OR (s.id = 3 AND a.id = 4) GROUP BY ();
>>
> Yeah, the last fix can't cover this case, because the
> otherrel->baserestrictinfo is NIL when trying to remove outerjoin rel
> from phv.
> The the otherrel->baserestrictinfo would be assigned when calling
> extract_restriction_or_clauses() in query_planner().
> But in extract_restriction_or_clauses(), we had no way to make the thing right.
>
>> My idea would be to put a bitmapset into remove_rel_from_query with the
>> seen ones and recurse removing it from the rinfo. I attached a sketch of
>> my idea. But maybe our have a better one.
> It seems that we have to process otherrel's baserestrictinfo and
> joininfo if the query involves a partition table.
The same should be true for union statements, plain inheritance and
pretty much anything, which creates an append.
> If we ignore one of them in add_other_rels_to_query(), the rel that
> was removed is brought back to the child rel.
> Then the crash would happen.
>
> I took a quick look at this patch. It seems workable.

Thank you, reviews are valuable!

Regards
Arne