Message-ID: <2d59d7d6-6afe-4565-8ff7-ae764651589a@gmail.com>
Date: Tue, 26 May 2026 19:52:03 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: BUG #19493: Assertion failure in pg_plan_advice with EXISTS
 subquery and DO_NOT_SCAN advice
To: n.kalinin@postgrespro.ru, pgsql-bugs@lists.postgresql.org,
 PG Bug reporting form <noreply@postgresql.org>
References: <19493-5878eac7a2525c23@postgresql.org>
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From: Pierre Forstmann <pierre.forstmann@gmail.com>
In-Reply-To: <19493-5878eac7a2525c23@postgresql.org>
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 <https://www.postgresql.org/message-id/2d59d7d6-6afe-4565-8ff7-ae764651589a%40gmail.com>
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Hello,

I am not sure pg_plan_advice is supported with PG 18.4 ?

I cannot reproduce with latest commit from PG 19 master branch:

$ git log -n 1
commit 61ea5cc6a61ff9eb8b3d7b055e507a726e5856c7 (HEAD -> master, 
origin/master, origin/HEAD)
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date:   Tue May 26 11:58:25 2026 -0400

     Add stack depth check to QueueFKConstraintValidation().

     QueueFKConstraintValidation() recurses through the partition hierarchy
     to queue child constraint validations and to mark child rows as
     validated.  With a sufficiently deep partition tree, this can result
     in a stack-overflow crash.  Defend against that as we do elsewhere.

     Bug: #19482
     Reported-by: Alexander Lakhin <exclusion@gmail.com>
     Author: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
     Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
     Discussion: https://postgr.es/m/19482-4cc37cbf52d55235@postgresql.org
     Backpatch-through: 18

postgres=# select version();
                                                    version
--------------------------------------------------------------------------------------------------------------
  PostgreSQL 19devel on x86_64-pc-linux-gnu, compiled by gcc (GCC) 
11.5.0 20240719 (Red Hat 11.5.0-11), 64-bit
(1 row)

postgres=#

I tested with:

DROP TABLE a;
DROP TABLE
DROP TABLE b;
DROP TABLE
LOAD 'pg_plan_advice';
LOAD
CREATE TABLE a(i int);
CREATE TABLE
CREATE TABLE b(i int);
CREATE TABLE
SET pg_plan_advice.feedback_warnings = on;
SET
SET pg_plan_advice.advice = 'DO_NOT_SCAN((a))';
SET
EXPLAIN
SELECT *
FROM a
WHERE EXISTS (
     SELECT 1
     FROM b
     WHERE b.i = a.i
);
psql:bug.sql:19: WARNING:  supplied plan advice was not enforced
DETAIL:  advice DO_NOT_SCAN((a)) feedback is "matched, failed"
                               QUERY PLAN
-----------------------------------------------------------------------
  Hash Join  (cost=46.38..102.75 rows=1275 width=4)
    Hash Cond: (a.i = b.i)
    ->  Seq Scan on a  (cost=0.00..35.50 rows=2550 width=4)
          Disabled: true
    ->  Hash  (cost=43.88..43.88 rows=200 width=4)
          ->  HashAggregate  (cost=41.88..43.88 rows=200 width=4)
                Group Key: b.i
                ->  Seq Scan on b  (cost=0.00..35.50 rows=2550 width=4)
  Supplied Plan Advice:
    DO_NOT_SCAN((a)) /* matched, failed */
(10 rows)


Le 26/05/2026 à 16:44, PG Bug reporting form a écrit :
> The following bug has been logged on the website:
>
> Bug reference:      19493
> Logged by:          Nikita Kalinin
> Email address:      n.kalinin@postgrespro.ru
> PostgreSQL version: 18.4
> Operating system:   Fedora 44
> Description:
>
> Hi,
> I found an assertion failure in pg_plan_advice.
> Reproducer:
>
> LOAD 'pg_plan_advice';
>
> CREATE TABLE a(i int);
> CREATE TABLE b(i int);
>
> SET pg_plan_advice.feedback_warnings = on;
> SET pg_plan_advice.advice = 'DO_NOT_SCAN((a))';
>
> EXPLAIN
> SELECT *
> FROM a
> WHERE EXISTS (
>      SELECT 1
>      FROM b
>      WHERE b.i = a.i
> );
>
> Result:
> 2026-05-26 21:36:46.452 +07 [83331] LOG:  database system is ready to accept
> connections
> TRAP: failed Assert("target->ttype == PGPA_TARGET_IDENTIFIER"), File:
> "pgpa_trove.c", Line: 182, PID: 83390
> postgres: nkpit postgres [local] EXPLAIN(ExceptionalCondition+0x57)
> [0xa2d077]
> /tmp/pg/lib/postgresql/pg_plan_advice.so(+0xb0b2) [0x7fb2c06440b2]
> /tmp/pg/lib/postgresql/pg_plan_advice.so(+0x533f) [0x7fb2c063e33f]
> postgres: nkpit postgres [local] EXPLAIN(standard_planner+0x1ff) [0x7b51ff]
> ...
> Backtrace:
> #0  __pthread_kill_implementation (threadid=<optimized out>,
> signo=signo@entry=6,
>      no_tid=no_tid@entry=0) at pthread_kill.c:44
> #1  0x00007fb2bf27a8d3 in __pthread_kill_internal (threadid=<optimized out>,
> signo=6)
>      at pthread_kill.c:89
> #2  0x00007fb2bf21f48e in __GI_raise (sig=sig@entry=6) at
> ../sysdeps/posix/raise.c:26
> #3  0x00007fb2bf2067b3 in __GI_abort () at abort.c:77
> #4  0x0000000000a2d098 in ExceptionalCondition (
>      conditionName=conditionName@entry=0x7fb2c0649828 "target->ttype ==
> PGPA_TARGET_IDENTIFIER",
>      fileName=fileName@entry=0x7fb2c064a184 "pgpa_trove.c",
> lineNumber=lineNumber@entry=182)
>      at assert.c:65
> #5  0x00007fb2c06440b2 in pgpa_build_trove (advice_items=0x32a59488) at
> pgpa_trove.c:182
> #6  0x00007fb2c063e33f in pgpa_planner_setup (glob=0x32985888,
> parse=0x32956d60,
>      query_string=0x329558b0 "EXPLAIN SELECT *\nFROM a\nWHERE EXISTS (SELECT
> 1 FROM b WHERE b.i = a.i);", cursorOptions=2048,
> tuple_fraction=0x7ffe98a152f0, es=0x32985308) at pgpa_planner.c:255
> #7  0x00000000007b51ff in standard_planner (parse=0x32956d60,
> query_string=<optimized out>,
>      cursorOptions=2048, boundParams=<optimized out>, es=0x32985308) at
> planner.c:533
> #8  0x00000000007b5a0d in planner (parse=parse@entry=0x32956d60,
>      query_string=query_string@entry=0x329558b0 "EXPLAIN SELECT *\nFROM
> a\nWHERE EXISTS (SELECT 1 FROM b WHERE b.i = a.i);",
> cursorOptions=cursorOptions@entry=2048,
>      boundParams=boundParams@entry=0x0, es=es@entry=0x32985308) at
> planner.c:342
> #9  0x00000000008c297d in pg_plan_query
> (querytree=querytree@entry=0x32956d60,
>      query_string=query_string@entry=0x329558b0 "EXPLAIN SELECT *\nFROM
> a\nWHERE EXISTS (SELECT 1 FROM b WHERE b.i = a.i);", cursorOptions=2048,
> boundParams=boundParams@entry=0x0,
>      es=es@entry=0x32985308) at postgres.c:917
> #10 0x000000000062ed1e in standard_ExplainOneQuery (query=0x32956d60,
>      cursorOptions=<optimized out>, into=0x0, es=0x32985308,
>      queryString=0x329558b0 "EXPLAIN SELECT *\nFROM a\nWHERE EXISTS (SELECT 1
> FROM b WHERE b.i = a.i);", params=0x0, queryEnv=0x0) at explain.c:359
> #11 0x000000000062ef8e in ExplainOneQuery (query=<optimized out>,
> cursorOptions=<optimized out>,
>      into=<optimized out>, es=<optimized out>, pstate=<optimized out>,
> params=<optimized out>)
>      at explain.c:315
> --Type <RET> for more, q to quit, c to continue without paging--c
> #12 0x000000000062f0ae in ExplainQuery (pstate=0x32982990, stmt=0x32956ba0,
> params=0x0,
>      dest=0x32985278) at ../../../src/include/nodes/nodes.h:178
> #13 0x00000000008c8819 in standard_ProcessUtility (pstmt=0x32956c50,
>      queryString=0x329558b0 "EXPLAIN SELECT *\nFROM a\nWHERE EXISTS (SELECT 1
> FROM b WHERE b.i = a.i);", readOnlyTree=<optimized out>,
> context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0,
>      dest=0x32985278, qc=0x7ffe98a15660) at utility.c:871
> #14 0x00000000008c6b8d in PortalRunUtility (portal=portal@entry=0x329f91e0,
> pstmt=0x32956c50,
>      isTopLevel=isTopLevel@entry=true,
> setHoldSnapshot=setHoldSnapshot@entry=true,
>      dest=dest@entry=0x32985278, qc=qc@entry=0x7ffe98a15660) at pquery.c:1149
> #15 0x00000000008c7060 in FillPortalStore (portal=portal@entry=0x329f91e0,
>      isTopLevel=isTopLevel@entry=true) at
> ../../../src/include/nodes/nodes.h:178
> #16 0x00000000008c737d in PortalRun (portal=portal@entry=0x329f91e0,
>      count=count@entry=9223372036854775807, isTopLevel=isTopLevel@entry=true,
>      dest=dest@entry=0x32a690d8, altdest=altdest@entry=0x32a690d8,
> qc=qc@entry=0x7ffe98a15830)
>      at pquery.c:756
> #17 0x00000000008c2f48 in exec_simple_query (
>      query_string=0x329558b0 "EXPLAIN SELECT *\nFROM a\nWHERE EXISTS (SELECT
> 1 FROM b WHERE b.i = a.i);") at postgres.c:1290
> #18 0x00000000008c4a21 in PostgresMain (dbname=<optimized out>,
> username=<optimized out>)
>      at postgres.c:4856
> #19 0x00000000008bea1d in BackendMain (startup_data=<optimized out>,
>      startup_data_len=<optimized out>) at backend_startup.c:124
> #20 0x00000000007fea2e in postmaster_child_launch (child_type=<optimized
> out>, child_slot=1,
>      startup_data=startup_data@entry=0x7ffe98a15c80,
> startup_data_len=startup_data_len@entry=24,
>      client_sock=client_sock@entry=0x7ffe98a15ca0) at launch_backend.c:268
> #21 0x0000000000802436 in BackendStartup (client_sock=0x7ffe98a15ca0) at
> postmaster.c:3627
> #22 ServerLoop () at postmaster.c:1728
> #23 0x0000000000803ef9 in PostmasterMain (argc=argc@entry=3,
> argv=argv@entry=0x328ff080)
>      at postmaster.c:1415
> #24 0x00000000004a1a68 in main (argc=3, argv=0x328ff080) at main.c:231
>
>
>
>