Re[2]: LISTEN/NOTIFY ultra slow speed

[Арсен Арутюнян <arutar@xxxxx>]

i looked at the file "\src\backend\commands\async.c"

there is a check for duplicate messages

 

/******** PG 10

if (AsyncExistsPendingNotify(channel, payload))

return;

***********/

 

/******** PG 13

if (AsyncExistsPendingNotify(n))

{

…...

}

***********/

Is this slowdown related to this check?

Is it possible to skip the check if I'm absolutely sure the message is unique?

 

 

--
Arsen Arutyunyan

 

 

Вторник, 15 марта 2022, 10:34 +03:00 от Арсен Арутюнян <arutar@xxxxx>:
 

 

1)

select version();

                          version

------------------------------------------------------------

 PostgreSQL 10.6, compiled by Visual C++ build 1800, 64-bit

 

2) $PGDATA/pg_notify/

Sometimes this folder is empty, sometimes it contains the file I have attached. The file is always less than 200kb

 

 

--
Arsen Arutyunyan

 

 

Понедельник, 14 марта 2022, 15:53 +03:00 от Арсен Арутюнян <arutar@xxxxx>:
 

    Hello! I'm having trouble with LISTEN/NOTIFY speed. Now I have about 100-200 (few?) clients who are actively messaging. But recently I started to notice a drop in speed. Changing the log_min_duration_statement parameter did not show slow queries in the log.

    As it turned out, the pg_notify(text ,text) function

          or the

          NOTIFY text, 'text' queries takes an extremely long time (0.7-1.5sec),

    but the select pg_notification_queue_usage() query always returns 0.

Please tell me what's the matter, where did I make a mistake? 

What needs to be done to increase the speed of adding to the message queue?

 

--
Arsen Arutyunyan

|What PG version is this exactly?  What is in $PGDATA/pg_notify/ ?

|            regards, tom lane