Re: NOTIFY does not work as expected
| От | Jeff Janes |
|---|---|
| Тема | Re: NOTIFY does not work as expected |
| Дата | |
| Msg-id | CAMkU=1zCfdxGBcm7N=Twr7bz4KTmYZbEhq=f-VaNmP6d4ry-Tw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: NOTIFY does not work as expected (Andres Freund <andres@anarazel.de>) |
| Ответы |
Re: NOTIFY does not work as expected
|
| Список | pgsql-bugs |
On Wed, Jul 4, 2018 at 2:30 PM, Andres Freund <andres@anarazel.de> wrote:
Hi,
On 2018-07-04 08:50:12 -0400, Jeff Janes wrote:
> Reading through the comments touched by the commit, it seems obvious what
> the bug is. It says "cause the processing to occur just before we next go
> idle", but also says "This is called just *after* waiting for a frontend
> command", which is too late to be "before we next go idle"
I've not looked at this issue in depth yet. So I might be completely off
base. But I'm confused by your comment - we're doing it *after*,
because we do a non-blocking read. And the latch will notify us
(event.events & WL_LATCH_SET) if there was a read.
We get a signal while we are busy. We set the flag and the latch. The latch
wakes us up, but since we are busy (in a transaction, specifically) we don't
do anything. Later, the transaction ends and we are about to go idle, but
no one checks the flag again. We start a read using the latch mechanism, but
the flag notifyInterruptPending being set true from a now-long-gone signal is not on
the list of things the latch wakes us for. It is technically a non-blocking read but from
the perspective if the pending notify message it is a blocking read, unless another
signal comes along and rescues us.
Cheers,
Jeff
В списке pgsql-bugs по дате отправления: