BUG #18902: TRAP:: failed Assert("!is_sorted") in File: "createplan.c"

The following bug has been logged on the website:

Bug reference: 18902
Logged by: Nikita Kalinin
Email address: n(dot)kalinin(at)postgrespro(dot)ru
PostgreSQL version: 17.4
Operating system: ubuntu 22.04
Description:

Hello!
After I built PostgreSQL like this:
`./configure --enable-tap-tests --enable-debug --with-openssl
--enable-cassert --prefix=/tmp/pg && make -j8 && make install`
And executed the following script:
```
CREATE EXTENSION postgres_fdw;

CREATE SERVER testserver1 FOREIGN DATA WRAPPER postgres_fdw;
DO $d$
BEGIN
EXECUTE $$CREATE SERVER loopback FOREIGN DATA WRAPPER postgres_fdw
OPTIONS (dbname '$$||current_database()||$$',
port '$$||current_setting('port')||$$'
)$$;
EXECUTE $$CREATE SERVER loopback2 FOREIGN DATA WRAPPER
postgres_fdw
OPTIONS (dbname '$$||current_database()||$$',
port '$$||current_setting('port')||$$'
)$$;
EXECUTE $$CREATE SERVER loopback3 FOREIGN DATA WRAPPER
postgres_fdw
OPTIONS (dbname '$$||current_database()||$$',
port '$$||current_setting('port')||$$'
)$$;
END;
$d$;

CREATE USER MAPPING FOR public SERVER testserver1
OPTIONS (user 'value', password 'value');
CREATE USER MAPPING FOR CURRENT_USER SERVER loopback;
CREATE USER MAPPING FOR CURRENT_USER SERVER loopback2;
CREATE USER MAPPING FOR public SERVER loopback3;

CREATE TYPE user_enum AS ENUM ('foo', 'bar', 'buz');
CREATE FOREIGN TABLE ft1 (
c0 int,
c1 int NOT NULL,
c2 int NOT NULL,
c3 text,
c4 timestamptz,
c5 timestamp,
c6 varchar(10),
c7 char(10) default 'ft1',
c8 user_enum
) SERVER loopback;
ALTER FOREIGN TABLE ft1 DROP COLUMN c0;

CREATE FOREIGN TABLE ft2 (
c1 int NOT NULL,
c2 int NOT NULL,
cx int,
c3 text,
c4 timestamptz,
c5 timestamp,
c6 varchar(10),
c7 char(10) default 'ft2',
c8 user_enum
) SERVER loopback;
ALTER FOREIGN TABLE ft2 DROP COLUMN cx;

CREATE FOREIGN TABLE ft4 (
c1 int NOT NULL,
c2 int NOT NULL,
c3 text
) SERVER loopback OPTIONS (schema_name 'S 1', table_name 'T 3');

CREATE FOREIGN TABLE ft5 (
c1 int NOT NULL,
c2 int NOT NULL,
c3 text
) SERVER loopback OPTIONS (schema_name 'S 1', table_name 'T 4');

CREATE TABLE local_tbl (c1 int NOT NULL, c2 int NOT NULL, c3 text,
CONSTRAINT local_tbl_pkey PRIMARY KEY (c1));
INSERT INTO local_tbl SELECT id, id % 10, to_char(id, 'FM0000') FROM
generate_series(1, 1000) id;
ANALYZE local_tbl;
SET enable_nestloop TO false;
SET enable_hashjoin TO false;
EXPLAIN (VERBOSE, COSTS OFF)
SELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2
= ft4.c1
AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND
ft2.c1 < 100 FOR UPDATE;
```

I got a coredump:
```
Core was generated by `postgres: test postgres [local] EXPLAIN
'.
Program terminated with signal SIGABRT, Aborted.
#0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized
out>) at ./nptl/pthread_kill.c:44

warning: 44 ./nptl/pthread_kill.c: No such file or directory
(gdb) bt
#0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimized
out>) at ./nptl/pthread_kill.c:44
#1 __pthread_kill_internal (signo=6, threadid=<optimized out>) at
./nptl/pthread_kill.c:78
#2 __GI___pthread_kill (threadid=<optimized out>, signo=signo(at)entry=6) at
./nptl/pthread_kill.c:89
#3 0x000073517d44527e in __GI_raise (sig=sig(at)entry=6) at
../sysdeps/posix/raise.c:26
#4 0x000073517d4288ff in __GI_abort () at ./stdlib/abort.c:79
#5 0x0000603f0b24f1af in ExceptionalCondition
(conditionName=conditionName(at)entry=0x603f0b2cd558 "!is_sorted",
fileName=fileName(at)entry=0x603f0b2cdce3 "createplan.c",
lineNumber=lineNumber(at)entry=4538) at assert.c:66
#6 0x0000603f0aff7e88 in create_mergejoin_plan (best_path=0x603f3881caa8,
root=0x603f3871c738) at createplan.c:4538
#7 create_join_plan (best_path=0x603f3881caa8, root=0x603f3871c738) at
createplan.c:1089
#8 create_plan_recurse (root=0x603f3871c738, best_path=0x603f3881caa8,
flags=<optimized out>) at createplan.c:418
#9 0x0000603f0aff94f1 in create_foreignscan_plan (scan_clauses=0x0,
tlist=0x603f3882d938, best_path=0x603f3881cef8,
root=0x603f3871c738) at createplan.c:4128
#10 create_scan_plan (root=0x603f3871c738, best_path=0x603f3881cef8,
flags=<optimized out>) at createplan.c:787
#11 0x0000603f0aff6c73 in create_mergejoin_plan (best_path=0x603f388289e8,
root=0x603f3871c738) at createplan.c:4468
#12 create_join_plan (best_path=0x603f388289e8, root=0x603f3871c738) at
createplan.c:1089
#13 create_plan_recurse (root=0x603f3871c738, best_path=0x603f388289e8,
flags=<optimized out>) at createplan.c:418
#14 0x0000603f0aff7916 in create_projection_plan (flags=1,
best_path=0x603f3882c558, root=0x603f3871c738) at createplan.c:2056
#15 create_plan_recurse (root=0x603f3871c738, best_path=0x603f3882c558,
flags=1) at createplan.c:434
#16 0x0000603f0aff5a93 in create_lockrows_plan (flags=1,
best_path=0x603f3882c988, root=0x603f3871c738) at createplan.c:2792
#17 create_plan_recurse (root=0x603f3871c738, best_path=0x603f3882c988,
flags=1) at createplan.c:527
#18 0x0000603f0aff8529 in create_plan (root=root(at)entry=0x603f3871c738,
best_path=<optimized out>) at createplan.c:349
#19 0x0000603f0b009dfa in standard_planner (parse=0x603f387c0818,
query_string=<optimized out>, cursorOptions=2048,
boundParams=0x0) at planner.c:436
#20 0x0000603f0b00a4b5 in planner (parse=parse(at)entry=0x603f387c0818,
--Type <RET> for more, q to quit, c to continue without paging--c
query_string=query_string(at)entry=0x603f386c3000 "EXPLAIN (VERBOSE, COSTS
OFF)\nSELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND
ft1.c2 = ft4.c1\n AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND
ft1.c1 < 100 AND ft2.c1 < 100 F"...,
cursorOptions=cursorOptions(at)entry=2048,
boundParams=boundParams(at)entry=0x0) at planner.c:294
#21 0x0000603f0b0fd2cb in pg_plan_query
(querytree=querytree(at)entry=0x603f387c0818,
query_string=query_string(at)entry=0x603f386c3000 "EXPLAIN (VERBOSE, COSTS
OFF)\nSELECT * FROM ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND
ft1.c2 = ft4.c1\n AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND
ft1.c1 < 100 AND ft2.c1 < 100 F"...,
cursorOptions=cursorOptions(at)entry=2048,
boundParams=boundParams(at)entry=0x0) at postgres.c:900
#22 0x0000603f0aea1a74 in standard_ExplainOneQuery (query=0x603f387c0818,
cursorOptions=2048, into=0x0, es=0x603f387d3308,
queryString=0x603f386c3000 "EXPLAIN (VERBOSE, COSTS OFF)\nSELECT * FROM
ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1\n
AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 <
100 F"..., params=0x0,
queryEnv=0x0) at explain.c:353
#23 0x0000603f0aea1c4c in ExplainOneQuery (query=<optimized out>,
cursorOptions=<optimized out>, into=<optimized out>,
es=<optimized out>, pstate=<optimized out>, params=<optimized out>) at
explain.c:309
#24 0x0000603f0aea1d6e in ExplainQuery (pstate=0x603f387e67c8,
stmt=0x603f387c0658, params=0x0, dest=0x603f387e6738)
at ../../../src/include/nodes/nodes.h:178
#25 0x0000603f0b10342b in standard_ProcessUtility (pstmt=0x603f387c0708,
queryString=0x603f386c3000 "EXPLAIN (VERBOSE, COSTS OFF)\nSELECT * FROM
ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1\n
AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 <
100 F"...,
readOnlyTree=<optimized out>, context=PROCESS_UTILITY_TOPLEVEL,
params=0x0, queryEnv=0x0, dest=0x603f387e6738,
qc=0x7fffa93ebd50) at utility.c:866
#26 0x0000603f0b1016df in PortalRunUtility
(portal=portal(at)entry=0x603f38742a90, pstmt=0x603f387c0708,
isTopLevel=true,
setHoldSnapshot=setHoldSnapshot(at)entry=true,
dest=dest(at)entry=0x603f387e6738, qc=qc(at)entry=0x7fffa93ebd50) at
pquery.c:1185
#27 0x0000603f0b101bd4 in FillPortalStore
(portal=portal(at)entry=0x603f38742a90, isTopLevel=isTopLevel(at)entry=true)
at ../../../src/include/nodes/nodes.h:178
#28 0x0000603f0b101f0d in PortalRun (portal=portal(at)entry=0x603f38742a90,
count=count(at)entry=9223372036854775807,
isTopLevel=isTopLevel(at)entry=true, dest=dest(at)entry=0x603f387f5da8,
altdest=altdest(at)entry=0x603f387f5da8,
qc=qc(at)entry=0x7fffa93ebf30) at pquery.c:792
#29 0x0000603f0b0fd826 in exec_simple_query (
query_string=0x603f386c3000 "EXPLAIN (VERBOSE, COSTS OFF)\nSELECT * FROM
ft1, ft2, ft4, ft5, local_tbl WHERE ft1.c1 = ft2.c1 AND ft1.c2 = ft4.c1\n
AND ft1.c2 = ft5.c1 AND ft1.c2 = local_tbl.c1 AND ft1.c1 < 100 AND ft2.c1 <
100 F"...) at postgres.c:1274
#30 0x0000603f0b0ff44a in PostgresMain (dbname=<optimized out>,
username=<optimized out>) at postgres.c:4771
#31 0x0000603f0b0f97e3 in BackendMain (startup_data=<optimized out>,
startup_data_len=<optimized out>) at backend_startup.c:124
#32 0x0000603f0b048fb2 in postmaster_child_launch (child_type=<optimized
out>, child_slot=1,
startup_data=startup_data(at)entry=0x7fffa93ec3e0,
startup_data_len=startup_data_len(at)entry=24,
client_sock=client_sock(at)entry=0x7fffa93ec400) at launch_backend.c:290
#33 0x0000603f0b04ce0e in BackendStartup (client_sock=0x7fffa93ec400) at
postmaster.c:3580
#34 ServerLoop () at postmaster.c:1702
#35 0x0000603f0b04e7ee in PostmasterMain (argc=argc(at)entry=3,
argv=argv(at)entry=0x603f3867d130) at postmaster.c:1400
#36 0x0000603f0ad1d76e in main (argc=3, argv=0x603f3867d130) at main.c:227
```

logfile:
```
2025-04-23 04:36:23.099 UTC [162772] LOG: database system is ready to
accept connections
TRAP: failed Assert("!is_sorted"), File: "createplan.c", Line: 4538, PID:
162868
postgres: test postgres [local]
EXPLAIN(ExceptionalCondition+0x70)[0x603f0b24f190]
postgres: test postgres [local] EXPLAIN(+0x45de88)[0x603f0aff7e88]
postgres: test postgres [local] EXPLAIN(+0x45f4f1)[0x603f0aff94f1]
postgres: test postgres [local] EXPLAIN(+0x45cc73)[0x603f0aff6c73]
postgres: test postgres [local] EXPLAIN(+0x45d916)[0x603f0aff7916]
postgres: test postgres [local] EXPLAIN(+0x45ba93)[0x603f0aff5a93]
postgres: test postgres [local] EXPLAIN(create_plan+0x29)[0x603f0aff8529]
postgres: test postgres [local]
EXPLAIN(standard_planner+0x15a)[0x603f0b009dfa]
postgres: test postgres [local] EXPLAIN(planner+0x35)[0x603f0b00a4b5]
postgres: test postgres [local]
EXPLAIN(pg_plan_query+0x4b)[0x603f0b0fd2cb]
postgres: test postgres [local]
EXPLAIN(standard_ExplainOneQuery+0x124)[0x603f0aea1a74]
postgres: test postgres [local] EXPLAIN(+0x307c4c)[0x603f0aea1c4c]
postgres: test postgres [local] EXPLAIN(ExplainQuery+0xfe)[0x603f0aea1d6e]
postgres: test postgres [local]
EXPLAIN(standard_ProcessUtility+0x65b)[0x603f0b10342b]
postgres: test postgres [local] EXPLAIN(+0x5676df)[0x603f0b1016df]
postgres: test postgres [local] EXPLAIN(+0x567bd4)[0x603f0b101bd4]
postgres: test postgres [local] EXPLAIN(PortalRun+0x2dd)[0x603f0b101f0d]
postgres: test postgres [local] EXPLAIN(+0x563826)[0x603f0b0fd826]
postgres: test postgres [local]
EXPLAIN(PostgresMain+0x17da)[0x603f0b0ff44a]
postgres: test postgres [local] EXPLAIN(BackendMain+0x53)[0x603f0b0f97e3]
postgres: test postgres [local]
EXPLAIN(postmaster_child_launch+0x102)[0x603f0b048fb2]
postgres: test postgres [local] EXPLAIN(+0x4b2e0e)[0x603f0b04ce0e]
postgres: test postgres [local]
EXPLAIN(PostmasterMain+0xd3e)[0x603f0b04e7ee]
postgres: test postgres [local] EXPLAIN(main+0x1ce)[0x603f0ad1d76e]
/lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca)[0x73517d42a1ca]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x8b)[0x73517d42a28b]
postgres: test postgres [local] EXPLAIN(_start+0x25)[0x603f0ad1daf5]
2025-04-23 04:36:35.570 UTC [162772] LOG: client backend (PID 162868) was
terminated by signal 6: Aborted
```

The commit where this was reproduced:
e0f373ee42a40a41bdfc025a1641d351580991c4

```
postgres=# select version();
version
----------------------------------------------------------------------------------------------------------
PostgreSQL 18devel on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu
13.3.0-6ubuntu2~24.04) 13.3.0, 64-bit
(1 row)
```