Hi hackers,
I noticed an inconsistent update when executing MERGE commands, which
looks more like a bug.
In my test example, the value of 'val' should increase in an ascending
monotonous sequence.
Test system
===========
- Architecture: x86_64
- OS: Ubuntu 24.04.3 LTS (Noble Numbat)
- Tested postgres version(s):
- latest 17 (17.6)
Steps to reproduce
==================
postgres=# create table t_merge (id int primary key, val int);
CREATE TABLE
postgres=# create table t_merge_chk (val int primary key);
CREATE TABLE
postgres=# insert into t_merge values (1,0);
INSERT 0 1
pgbench --no-vacuum --exit-on-abort -c 10 --file=/dev/stdin <<'EOF'
begin;
merge into t_merge t
using (select 1 id) s on (t.id = s.id)
when matched then update set val = t.val + 1
returning val \gset
-- Checking the uniqueness of a value
insert into t_merge_chk (val) values (:val);
commit;
EOF
pgbench: error: client 3 script 0 aborted in command 2 query 0:
ERROR: duplicate key value violates unique constraint "t_merge_chk_pkey"
DETAIL: Key (val)=(2) already exists.
What do you think about this?
Best regards,
Dmitry
