Josh Berkus wrote:
the behavior was the same up to the second UPDATE on Process 2, at
which point there was no deadlock. Process 2 was able to commit,
at which point Process 1 failed with:
ERROR: could not serialize access due to concurrent update
Does this happen immediately, not
Kevin,
In the for what it's worth department, I tried out the current
Serializable Snapshot Isolation (SSI) patch with this test case at
the SERIALIZABLE transaction isolation level. Rather than defining
a foreign key, I ran the queries which an SSI implementation in a
SERIALIZABLE-only
On 8/20/10 7:18 AM, Tom Lane wrote:
It does go through without any deadlock, *if* there is no foreign key
involved. You didn't tell us exactly what the FK relationship is, but
I suspect the reason for the deadlock is that one process is trying to
update a row that references some row already
In my example,
Process 1:Process 2:
BEGIN;
SELECT pg_backend_pid();
BEGIN;
SELECT
pg_backend_pid();
UPDATE A SET Col1 = 1 WHERE AID = 1;
SELECT * FROM
Another question, Tom referred to a comment in
src/backend/command/trigger.c.
My example does not contain any triggers, nor insert commands. Is the
trigger.c-comment still relevant or is it a misunderstanding?
It's relevant for how the FKs are handled.
--
Josh Berkus j...@agliodbs.com wrote:
That's correct. This is the generic example I was talking about
earlier on -hackers. I'm not certain it's a bug per spec; I
wanted to talk through with Kevin what we *should* be doing in
this situation.
I'm certainly happy to address what impact the
In principle we don't need to sharelock the referencing row in either
update in this example, since the original row version is still there.
The problem is to know that, given the limited amount of information
available when performing the second update.
Ah, ok. I get it now.
Now to figure
I wrote:
If there are a lot of user-hostile behaviors there, it might be
worth looking at the possibility of bending the SSI techniques to
that end
In the for what it's worth department, I tried out the current
Serializable Snapshot Isolation (SSI) patch with this test case at
the
