Message-ID: <5e09da43-aaba-7ea7-0a51-a2eb981b058b@gmail.com>
Date: Thu, 23 Feb 2023 14:00:00 +0300
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Subject: Re: BUG #17803: Rule "ALSO INSERT ... SELECT ..." fails to substitute
 default values
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To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-bugs@lists.postgresql.org
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From: Alexander Lakhin <exclusion@gmail.com>
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22.02.2023 15:29, Dean Rasheed wrote:
> On Wed, 22 Feb 2023 at 12:00, Alexander Lakhin <exclusion@gmail.com> wrote:
>> CREATE RULE vr AS ON INSERT TO v DO ALSO INSERT INTO t SELECT NEW.b;
>> INSERT INTO v VALUES(10, -1), (20, DEFAULT);
>> SELECT * FROM v;
>>
>>    a  | b
>> ----+----
>>    10 | -1
>>    20 | -1
>>    -1 | -1
>>       | -1
>>
> Yes, that's correct. Or at least that's the way it's always been. We
> even have regression tests similar to that.

Thanks for the explanation! I agree that there must be strong reasons to
change a well-known and accepted behavior.
Please look at another anomaly, probably not related to the initial one,
but related to INSERT VALUES(...), (...), as I can see:
CREATE TABLE t (a int, b int DEFAULT -1);
CREATE VIEW v AS SELECT * FROM t;

CREATE RULE vr AS ON INSERT TO v DO ALSO INSERT INTO t
   SELECT * FROM (SELECT a FROM t WHERE NEW.a = t.a) tt;

INSERT INTO v VALUES (1), (2);
Leads to:
Core was generated by `postgres: law regression [local] 
INSERT                                       '.
Program terminated with signal SIGABRT, Aborted.

warning: Section `.reg-xstate/1345067' in core file too small.
#0  __pthread_kill_implementation (no_tid=0, signo=6, 
threadid=140349553121088) at ./nptl/pthread_kill.c:44
44      ./nptl/pthread_kill.c: No such file or directory.
(gdb) bt
#0  __pthread_kill_implementation (no_tid=0, signo=6, 
threadid=140349553121088) at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=6, threadid=140349553121088) at 
./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=140349553121088, signo=signo@entry=6) 
at ./nptl/pthread_kill.c:89
#3  0x00007fa5acf33476 in __GI_raise (sig=sig@entry=6) at 
../sysdeps/posix/raise.c:26
#4  0x00007fa5acf197f3 in __GI_abort () at ./stdlib/abort.c:79
#5  0x000055643e045db9 in ExceptionalCondition 
(conditionName=0x55643e1fc08d "root->hasLateralRTEs",
     fileName=0x55643e1fbd1a "initsplan.c", lineNumber=2208) at assert.c:66
#6  0x000055643dd1211b in distribute_qual_to_rels (root=0x55643ed3d228, 
clause=0x55643ed5c130,
     jtitem=0x55643ed5d130, sjinfo=0x0, security_level=0, 
qualscope=0x55643ed5d2c0, ojscope=0x0,
     outerjoin_nonnullable=0x0, allow_equivalence=true, has_clone=false, 
is_clone=false,
     postponed_oj_qual_list=0x0) at initsplan.c:2208
#7  0x000055643dd11fcf in distribute_quals_to_rels (root=0x55643ed3d228, 
clauses=0x55643ed5c180,
     jtitem=0x55643ed5d130, sjinfo=0x0, security_level=0, 
qualscope=0x55643ed5d2c0, ojscope=0x0,
     outerjoin_nonnullable=0x0, allow_equivalence=true, has_clone=false, 
is_clone=false,
     postponed_oj_qual_list=0x0) at initsplan.c:2113
#8  0x000055643dd1073c in deconstruct_distribute (root=0x55643ed3d228, 
jtitem=0x55643ed5d130)
     at initsplan.c:1147
#9  0x000055643dd0f6ce in deconstruct_jointree (root=0x55643ed3d228) at 
initsplan.c:776
#10 0x000055643dd1476e in query_planner (root=0x55643ed3d228,
     qp_callback=0x55643dd1b11a <standard_qp_callback>, 
qp_extra=0x7ffc081eac20) at planmain.c:186
#11 0x000055643dd17319 in grouping_planner (root=0x55643ed3d228, 
tuple_fraction=0) at planner.c:1496
#12 0x000055643dd16998 in subquery_planner (glob=0x55643ed59468, 
parse=0x55643ec5e2c8, parent_root=0x0,
     hasRecursion=false, tuple_fraction=0) at planner.c:1065
#13 0x000055643dd14f36 in standard_planner (parse=0x55643ec5e2c8,
     query_string=0x55643ec5d568 "INSERT INTO v VALUES (1), (2);", 
cursorOptions=2048, boundParams=0x0)
     at planner.c:411
#14 0x000055643dd14c64 in planner (parse=0x55643ec5e2c8,
     query_string=0x55643ec5d568 "INSERT INTO v VALUES (1), (2);", 
cursorOptions=2048, boundParams=0x0)
     at planner.c:281
#15 0x000055643de60d18 in pg_plan_query (querytree=0x55643ec5e2c8,
     query_string=0x55643ec5d568 "INSERT INTO v VALUES (1), (2);", 
cursorOptions=2048, boundParams=0x0)
     at postgres.c:870
#16 0x000055643de60e75 in pg_plan_queries (querytrees=0x55643ed57828,
     query_string=0x55643ec5d568 "INSERT INTO v VALUES (1), (2);", 
cursorOptions=2048, boundParams=0x0)
     at postgres.c:962
#17 0x000055643de6128a in exec_simple_query (query_string=0x55643ec5d568 
"INSERT INTO v VALUES (1), (2);")
     at postgres.c:1159
#18 0x000055643de66456 in PostgresMain (dbname=0x55643ec95968 
"regression", username=0x55643ec5aaf8 "law")
     at postgres.c:4572
#19 0x000055643dd8a118 in BackendRun (port=0x55643ec860d0) at 
postmaster.c:4461
#20 0x000055643dd899a4 in BackendStartup (port=0x55643ec860d0) at 
postmaster.c:4189
#21 0x000055643dd85ce9 in ServerLoop () at postmaster.c:1779
#22 0x000055643dd85593 in PostmasterMain (argc=3, argv=0x55643ec58a30) 
at postmaster.c:1463
#23 0x000055643dc3f614 in main (argc=3, argv=0x55643ec58a30) at main.c:200

The more simple rule:
CREATE RULE vr AS ON INSERT TO v DO ALSO INSERT INTO t
   SELECT a FROM t WHERE NEW.a = t.a;
doesn't trigger the assertion failure,
and "INSERT INTO v VALUES (1);" with the complex rule too.

Maybe it's worth reporting it as another bug, and finish things with the
current one?
(Though I am still unsure, can we get
list_length(pt->jointree->fromlist) != 1 in the new condition?)

Best regards,
Alexander