BUG #18830: ExecInitMerge Segfault on MERGE

The following bug has been logged on the website:

Bug reference:      18830
Logged by:          Robins Tharakan
Email address:      tharakan@gmail.com
PostgreSQL version: Unsupported/Unknown
Operating system:   Ubuntu
Description:        

With this SQL (backtraces below), postgres starts to segfault starting at
cbc127917e.


SQL
===
CREATE AGGREGATE d(double precision ORDER BY anyelement) (
    SFUNC = ordered_set_transition_multi,
    STYPE = internal,
    FINALFUNC = rank_final);
CREATE TABLE e (
    a text,
    b integer
) PARTITION BY LIST (a);
CREATE TABLE f (
    a text,
    b integer
);
CREATE TABLE g (
    a text,
    b integer
);
CREATE VIEW h AS
 SELECT XMLSERIALIZE(DOCUMENT '<foo><bar>42</bar></foo>'AS text );
ALTER TABLE e ATTACH PARTITION f FOR VALUES IN ('a');
ALTER TABLE e ATTACH PARTITION g FOR VALUES IN ('b');

MERGE INTO e  USING h  ON a = xmlserialize WHEN NOT MATCHED THEN INSERT
VALUES (CAST(NULL AS text));


SQL Output
==========
$ psql -p 9999 postgres -f ../sqith/repro_final.sql
CREATE AGGREGATE
CREATE TABLE
CREATE TABLE
CREATE TABLE
CREATE VIEW
ALTER TABLE
ALTER TABLE
psql:../sqith/repro_final.sql:25: server closed the connection
unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
psql:../sqith/repro_final.sql:25: error: connection to server was lost



Error Log
=========
2025-03-03 06:55:54.014 ACDT [137463] LOG:  client backend (PID 137479) was
terminated by signal 11: Segmentation fault
2025-03-03 06:55:54.014 ACDT [137463] DETAIL:  Failed process was running:
MERGE INTO e  USING h  ON a = xmlserialize WHEN NOT MATCHED THEN INSERT
VALUES (CAST(NULL AS text));
2025-03-03 06:55:54.014 ACDT [137463] LOG:  terminating any other active
server processes


Commit
======
Checking (15a79c73111~0) - 15a79c7311 - fail
Checking (15a79c73111~10) - 424ededc58 - fail
Checking (15a79c73111~30) - 945a9e3832 - fail
Checking (15a79c73111~70) - a4e986ef5a - fail
Checking (15a79c73111~150) - 6a2275b895 - fail
Checking (15a79c73111~310) - 117f9f328e - Pass
Checking (15a79c73111~230) - c89525d57b - Pass
Checking (15a79c73111~190) - c366d2bdba - fail
Checking (15a79c73111~210) - fb056564ec - fail
Checking (15a79c73111~220) - 44ec095751 - Pass
Checking (15a79c73111~215) - cbc127917e - fail
Checking (15a79c73111~217) - 428fadb7e9 - Pass
Checking (15a79c73111~216) - 926c7fce03 - Pass
Offending Commit is cbc127917e - HEAD~215


BackTrace
=========
(gdb) bt
#0  ExecInitMerge (mtstate=0x599c6b260330, estate=0x599c6b260080) at
nodeModifyTable.c:3663
#1  0x0000599c2ca1ce11 in ExecInitModifyTable (node=0x599c6b282e08,
estate=0x599c6b260080, eflags=0) at nodeModifyTable.c:4889
#2  0x0000599c2c9d63a3 in ExecInitNode (node=0x599c6b282e08,
estate=0x599c6b260080, eflags=0) at execProcnode.c:177
#3  0x0000599c2c9cac66 in InitPlan (queryDesc=0x599c6b218ba0, eflags=0) at
execMain.c:985
#4  0x0000599c2c9c99f0 in standard_ExecutorStart (queryDesc=0x599c6b218ba0,
eflags=0) at execMain.c:259
#5  0x0000599c2c9c96fb in ExecutorStart (queryDesc=0x599c6b218ba0, eflags=0)
at execMain.c:135
#6  0x0000599c2ccb3925 in ProcessQuery (plan=0x599c6b284188,
    sourceText=0x599c6b16c4e0 "MERGE INTO e  USING h  ON a = xmlserialize
WHEN NOT MATCHED THEN INSERT VALUES (CAST(NULL AS text));", params=0x0,
queryEnv=0x0, dest=0x599c6b284308,
    qc=0x7ffc8bc1aaf0) at pquery.c:155
#7  0x0000599c2ccb546e in PortalRunMulti (portal=0x599c6b1ef0a0,
isTopLevel=true, setHoldSnapshot=false, dest=0x599c6b284308,
altdest=0x599c6b284308, qc=0x7ffc8bc1aaf0)
    at pquery.c:1271
#8  0x0000599c2ccb497a in PortalRun (portal=0x599c6b1ef0a0,
count=9223372036854775807, isTopLevel=true, dest=0x599c6b284308,
altdest=0x599c6b284308, qc=0x7ffc8bc1aaf0) at pquery.c:787
#9  0x0000599c2ccad440 in exec_simple_query (query_string=0x599c6b16c4e0
"MERGE INTO e  USING h  ON a = xmlserialize WHEN NOT MATCHED THEN INSERT
VALUES (CAST(NULL AS text));")
    at postgres.c:1271
#10 0x0000599c2ccb27ef in PostgresMain (dbname=0x599c6b1a6680 "smithreduce",
username=0x599c6b1a6668 "smith") at postgres.c:4691



BackTrace Full
==============
#0  ExecInitMerge (mtstate=0x599c6b260330, estate=0x599c6b260080) at
nodeModifyTable.c:3663
        mergeActionList = 0x599c6b281b70
        joinCondition = 0x0
        relationDesc = 0x599c2c9df7cb <ExecTypeFromTL+33>
        l = 0x100000000
        lc__state = {l = 0x599c6b281bc0, i = 0}
        node = 0x599c6b282e08
        rootRelInfo = 0x599c6b260f98
        resultRelInfo = 0x599c6b260f80
        econtext = 0x599c6b2695f8
        lc = 0x599c6b281bd8
        i = 1
        __func__ = "ExecInitMerge"
#1  0x0000599c2ca1ce11 in ExecInitModifyTable (node=0x599c6b282e08,
estate=0x599c6b260080, eflags=0) at nodeModifyTable.c:4889
        mtstate = 0x599c6b260330
        subplan = 0x599c6b282d78
        operation = CMD_MERGE
        nrels = 0
        resultRelations = 0x0
        withCheckOptionLists = 0x0
        returningLists = 0x0
        updateColnosLists = 0x0
        resultRelInfo = 0x599c6b260f80
        arowmarks = 0x0
        l = 0x0
        i = 0
        rel = 0x7be2ba49e368
        __func__ = "ExecInitModifyTable"
#2  0x0000599c2c9d63a3 in ExecInitNode (node=0x599c6b282e08,
estate=0x599c6b260080, eflags=0) at execProcnode.c:177
        result = 0x0
        subps = 0x599c6b282760
        l = 0x599c6b2608c0
        __func__ = "ExecInitNode"
#3  0x0000599c2c9cac66 in InitPlan (queryDesc=0x599c6b218ba0, eflags=0) at
execMain.c:985
        operation = CMD_MERGE
        plannedstmt = 0x599c6b284188
        plan = 0x599c6b282e08
        rangeTable = 0x599c6b283228
        estate = 0x599c6b260080
        planstate = 0x599c6b1ab310
        tupType = 0x599c6b2011f0
        l = 0x0
        i = 1
        __func__ = "InitPlan"


This (and bug #18828) found using SQLSmith / SQLReduce / creduce.