Server Crash due to assertion failure in _bt_check_unique()

Hi All,

I'm getting a server crash in *_bt_check_unique*() when running the
following test-case.

*Steps to reproduce the crash:*
*Step1:* Create a test table with primary key and insert some data in it.

create table t1 (a integer primary key, b text);

insert into t1 values (1, 'text1');
insert into t1 values (2, 'text2');
insert into t1 values (3, 'text3');
insert into t1 values (4, 'text4');
insert into t1 values (5, 'text5');

*Step2:* Start 3 backend sessions and run the following anonymous block in
each of them in parallel:
*Session 1:*
do $$
declare
begin
insert into t1 values (6, 'text6');
update t1 set b = 'text66' where a=6;
perform pg_sleep(7);
delete from t1 where a=6;
end $$;

*Session 2:*
do $$
begin
insert into t1 values (6, 'text6');
perform pg_sleep('7');
delete from t1 where a=6;
end $$;

*Session 3:*
do $$
begin
insert into t1 values (6, 'text6');
delete from t1 where a=6;
end $$;

Here is the backtrace for the crash:

#0 0x00007f096019f277 in raise () from /lib64/libc.so.6
#1 0x00007f09601a0968 in abort () from /lib64/libc.so.6
#2 0x0000000000a54296 in ExceptionalCondition (conditionName=0xafdbf8
"!(!_bt_isequal(itupdesc, itup_key, page, offset))",
errorType=0xafd75a "FailedAssertion", fileName=0xafd81f "nbtinsert.c",
lineNumber=386) at assert.c:54
#3 0x0000000000509b0a in _bt_check_unique (rel=0x7f096101a030,
insertstate=0x7ffcbd5db9d0, heapRel=0x7f0961017c00,
checkUnique=UNIQUE_CHECK_YES,
is_unique=0x7ffcbd5dba01, speculativeToken=0x7ffcbd5db9c8) at
nbtinsert.c:386
#4 0x00000000005096ab in _bt_doinsert (rel=0x7f096101a030, itup=0x27bedc0,
checkUnique=UNIQUE_CHECK_YES, heapRel=0x7f0961017c00) at nbtinsert.c:232
#5 0x0000000000514bb8 in btinsert (rel=0x7f096101a030,
values=0x7ffcbd5dbb50, isnull=0x7ffcbd5dbb30, ht_ctid=0x27be708,
heapRel=0x7f0961017c00,
checkUnique=UNIQUE_CHECK_YES, indexInfo=0x27be048) at nbtree.c:205
#6 0x000000000050752a in index_insert (indexRelation=0x7f096101a030,
values=0x7ffcbd5dbb50, isnull=0x7ffcbd5dbb30, heap_t_ctid=0x27be708,
heapRelation=0x7f0961017c00, checkUnique=UNIQUE_CHECK_YES,
indexInfo=0x27be048) at indexam.c:212
#7 0x00000000006e5d70 in ExecInsertIndexTuples (slot=0x27be6d8,
estate=0x27bd7a8, noDupErr=false, specConflict=0x0, arbiterIndexes=0x0)
at execIndexing.c:390
#8 0x000000000071f11f in ExecInsert (mtstate=0x27bdb60, slot=0x27be6d8,
planSlot=0x27be6d8, estate=0x27bd7a8, canSetTag=true) at
nodeModifyTable.c:587
#9 0x0000000000721696 in ExecModifyTable (pstate=0x27bdb60) at
nodeModifyTable.c:2175
.......

The following Assert statement in *_bt_check_unique* fails

>│386 *Assert(!_bt_isequal(itupdesc,
itup_key, page, offset));*

Upon quick look, it seems like the following git-commit has added above
Assert statement:

commit e5adcb789d80ba565ccacb1ed4341a7c29085238
Author: Peter Geoghegan <pg(at)bowt(dot)ie>
Date: Wed Mar 20 09:30:57 2019 -0700

Refactor nbtree insertion scankeys.

Use dedicated struct to represent nbtree insertion scan keys. Having a
dedicated struct makes the difference between search type scankeys and
insertion scankeys a lot clearer, and simplifies the signature of
several related functions. This is based on a suggestion by Andrey
Lepikhov.

....

Including Peter and Hekki in the CC as they are the main author of above
git-commit as per the commit message.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:*http://www.enterprisedb.com <http://www.enterprisedb.com/>*