Re: BUG #19493: Assertion failure in pg_plan_advice with EXISTS subquery and DO_NOT_SCAN advice

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(at)sss(dot)pgh(dot)pa(dot)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(at)gmail(dot)com>
    Author: Ayush Tiwari <ayushtiwari(dot)slg01(at)gmail(dot)com>
    Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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(dot)kalinin(at)postgrespro(dot)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(at)entry=6,
> no_tid=no_tid(at)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(at)entry=6) at
> ../sysdeps/posix/raise.c:26
> #3 0x00007fb2bf2067b3 in __GI_abort () at abort.c:77
> #4 0x0000000000a2d098 in ExceptionalCondition (
> conditionName=conditionName(at)entry=0x7fb2c0649828 "target->ttype ==
> PGPA_TARGET_IDENTIFIER",
> fileName=fileName(at)entry=0x7fb2c064a184 "pgpa_trove.c",
> lineNumber=lineNumber(at)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(at)entry=0x32956d60,
> query_string=query_string(at)entry=0x329558b0 "EXPLAIN SELECT *\nFROM
> a\nWHERE EXISTS (SELECT 1 FROM b WHERE b.i = a.i);",
> cursorOptions=cursorOptions(at)entry=2048,
> boundParams=boundParams(at)entry=0x0, es=es(at)entry=0x32985308) at
> planner.c:342
> #9 0x00000000008c297d in pg_plan_query
> (querytree=querytree(at)entry=0x32956d60,
> query_string=query_string(at)entry=0x329558b0 "EXPLAIN SELECT *\nFROM
> a\nWHERE EXISTS (SELECT 1 FROM b WHERE b.i = a.i);", cursorOptions=2048,
> boundParams=boundParams(at)entry=0x0,
> es=es(at)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(at)entry=0x329f91e0,
> pstmt=0x32956c50,
> isTopLevel=isTopLevel(at)entry=true,
> setHoldSnapshot=setHoldSnapshot(at)entry=true,
> dest=dest(at)entry=0x32985278, qc=qc(at)entry=0x7ffe98a15660) at pquery.c:1149
> #15 0x00000000008c7060 in FillPortalStore (portal=portal(at)entry=0x329f91e0,
> isTopLevel=isTopLevel(at)entry=true) at
> ../../../src/include/nodes/nodes.h:178
> #16 0x00000000008c737d in PortalRun (portal=portal(at)entry=0x329f91e0,
> count=count(at)entry=9223372036854775807, isTopLevel=isTopLevel(at)entry=true,
> dest=dest(at)entry=0x32a690d8, altdest=altdest(at)entry=0x32a690d8,
> qc=qc(at)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(at)entry=0x7ffe98a15c80,
> startup_data_len=startup_data_len(at)entry=24,
> client_sock=client_sock(at)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(at)entry=3,
> argv=argv(at)entry=0x328ff080)
> at postmaster.c:1415
> #24 0x00000000004a1a68 in main (argc=3, argv=0x328ff080) at main.c:231
>
>
>
>