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From: Tender Wang <tndrwang@gmail.com>
Date: Fri, 29 May 2026 10:03:50 +0800
Message-ID: 
 <CAHewXNkVe1TQ1gi0_PzJhXw82AGK85Jc8+sLgC_CdtOzP_v+GA@mail.gmail.com>
Subject: Re: BUG #19493: Assertion failure in pg_plan_advice with EXISTS
 subquery and DO_NOT_SCAN advice
To: pgsql-bugs@lists.postgresql.org
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Ayush Tiwari <ayushtiwari.slg01@gmail.com>,
	=?UTF-8?B?0JrQsNC70LjQvdC40L0g0J3QuNC60LjRgtCw?= <n.kalinin@postgrespro.ru>,
	Michael Paquier <michael@paquier.xyz>,
 Pierre Forstmann <pierre.forstmann@gmail.com>
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Hi all,

Ayush Tiwari <ayushtiwari.slg01@gmail.com> =E4=BA=8E2026=E5=B9=B45=E6=9C=88=
27=E6=97=A5=E5=91=A8=E4=B8=89 15:16=E5=86=99=E9=81=93=EF=BC=9A
>
> Hi,
>
> On Wed, 27 May 2026 at 09:20, Tender Wang <tndrwang@gmail.com> wrote:
>>
>> Hi, all
>>
>> I find an easier way as follows:
>> diff --git a/contrib/pg_plan_advice/pgpa_trove.c
>> b/contrib/pg_plan_advice/pgpa_trove.c
>> index ca69f3bd3df..64af4b1435b 100644
>> --- a/contrib/pg_plan_advice/pgpa_trove.c
>> +++ b/contrib/pg_plan_advice/pgpa_trove.c
>> @@ -179,7 +179,6 @@ pgpa_build_trove(List *advice_items)
>>                                          * but in the future this
>> might not be true, e.g. a custom
>>                                          * scan could replace a join.
>>                                          */
>> -                                       Assert(target->ttype =3D=3D
>> PGPA_TARGET_IDENTIFIER);
>>                                         pgpa_trove_add_to_slice(&trove->=
scan,
>>
>>                  item->tag, target);
>>                                 }
>
>
> Thanks for checking this.
>
> I agree that removing the assertion looks like the better approach.

I attached a patch to fix this issue.

In syntax.sql, I saw this:
"
-- Tags like SEQ_SCAN and NO_GATHER don't allow sublists at all; other tags=
,
-- except for JOIN_ORDER, allow at most one level of sublist. Hence, these
-- examples should error out.
"
So 'DO_NOT_SCAN((x))' is valid syntax. The original codes in
pgpa_build_trove() may
forget about this case. I added this syntax case to the syntax.sql.

I also added the query to scan.sql and adjusted the original comments.

--=20
Thanks,
Tender Wang

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