Serializable wrong?
-Hackers,
I came across this today [1], "
3 Results
In most respects, PostgreSQL behaved as expected: both read uncommitted and
read committed prevent write skew and aborted reads. We observed no
internal consistency violations. However, we have two surprising results to
report. The first is that PostgreSQL’s “repeatable read” is weaker than
repeatable read, at least as defined by Berenson, Adya, Bailis, et al. This
is not necessarily wrong: the ANSI SQL standard is ambiguous. The second
result, which is definitely wrong, is that PostgreSQL’s “serializable”
isolation level isn’t serializable: it allows G2-item during normal
operation. "
Thanks!
JD
On Fri, Jun 12, 2020 at 6:58 PM Joshua Drake <jd@commandprompt.com> wrote:
-Hackers,
I came across this today [1], "
3 ResultsIn most respects, PostgreSQL behaved as expected: both read uncommitted
and read committed prevent write skew and aborted reads. We observed no
internal consistency violations. However, we have two surprising results to
report. The first is that PostgreSQL’s “repeatable read” is weaker than
repeatable read, at least as defined by Berenson, Adya, Bailis, et al. This
is not necessarily wrong: the ANSI SQL standard is ambiguous. The second
result, which is definitely wrong, is that PostgreSQL’s “serializable”
isolation level isn’t serializable: it allows G2-item during normal
operation. "Thanks!
JD
Yes, this has been reported and is under discussion in pgsql-bugs list:
/messages/by-id/db7b729d-0226-d162-a126-8a8ab2dc4443@jepsen.io