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

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