On 2014-03-17 14:01:03 -0400, Tom Lane wrote:
> Andres Freund <andres@2ndquadrant.com> writes:
> > * I wonder if we should make the possible origins a bit more
> > general as it's perfectly possible to trigger the problem without
> > foreign keys. Maybe: "can arise when a table row that has been updated
> > is row locked; that can e.g. happen when foreign keys are used."
>
> IIUC, this case only occurs when using the new-in-9.3 types of
> nonexclusive row locks. I'm willing to bet that the number of
> applications using those is negligible; so I think it's all right to not
> mention that case explicitly, as long as the wording doesn't say that
> foreign keys are the *only* cause (which I didn't).
I actually think the issue could also occur with row locks of other
severities (is that the correct term?). Alvaro probably knows better,
but if I see correctly it's also triggerable if a backend waits for an
updating transaction to finish and follow_updates = true is passed to
heap_lock_tuple(). Which e.g. nodeLockRows.c does...
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services
