Re: NOTIFY does not work as expected

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От Andrey
Тема Re: NOTIFY does not work as expected
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Msg-id CAOYf6ecxnwBs2rxr82SzxVg1x_ypdz96KyOZjq_=uyRnmn4FqQ@mail.gmail.com
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Ответ на Re: NOTIFY does not work as expected  (Jeff Janes <jeff.janes@gmail.com>)
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man: "... if a listening session receives a notification signal while it is within a transaction, the notification event will not be delivered to its connected client until _just after_ the transaction is completed (either committed or aborted)."
Expected behavior is to deliver notification after pg_sleep is finished. Currently the one may hold opened connection (being idle and listening socket) for a long time, close it and never deliver the notification (if was busy while being notified).
All delivering problems were about overflowed queue, merging notifications and transactions handling. If we must not rely on delivering at all, then NOTIFY makes no sense.
вт, 3 июля 2018 г. в 3:37, Jeff Janes <jeff.janes@gmail.com>:
On Mon, Jul 2, 2018 at 4:33 PM, Andrey <parihaaraka@gmail.com> wrote:
PostgreSQL 9.6.9, 10.4 (broken):
A: listen test;
A: select pg_sleep(5);
    1
    2
B: notify test, 'test1';
    3
    4
    5
A: done
    6
    7
    8
    9
B: notify test, 'test2';
A:
* notification received:
  server process id: 2837
  channel: test
  payload: test
* notification received:
  server process id: 2837
  channel: test
  payload: test2

PostgreSQL 9.6.2 and earlier (workds as expected)
A: listen test;
A: select pg_sleep(5);
    1
    2
B: notify test, 'test1';
    3
    4
    5
A: done
A:
* notification received:
  server process id: 2837
  channel: test
  payload: test
    6
    7
    8
    9
B: notify test, 'test2';
A:
* notification received:
  server process id: 2837
  channel: test
  payload: test2

I don't think this is a bug.   I don't see that the docs promise one behavior over the other, so it is really a dealer's choice.  Also, I can't reliably reproduce the reported 9.6.2 behavior on my own 9.6.2 server.

Cheers,

Jeff

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