What does listen and notify do in PostgreSQL?
Listen and Notify provide a simple form of signal or interprocess communication mechanism for a collection of processes accessing the same PostgreSQL™ database. For more information on notifications consult the main server documentation. This section only deals with the JDBC specific aspects of notifications.
How does the listen notify and UNLISTEN function work?
Standard LISTEN, NOTIFY, and UNLISTEN commands are issued via the standard Statement interface. To retrieve and process retrieved notifications the Connection must be cast to the PostgreSQL™ specific extension interface PGConnection. From there the getNotifications () method can be used to retrieve any outstanding notifications.
Is there a listen / notify driver for Java?
From what I can tell, the JDBC drivers for LISTEN/NOTIFY in Java do NOT support true event-driven notifications. You have to poll the database every so often to see if there’s a new notification.
Listen and Notify provide a simple form of signal or interprocess communication mechanism for a collection of processes accessing the same PostgreSQL™ database. For more information on notifications consult the main server documentation.
How many notifications are in PostgreSQL tweet.activity?
Asynchronous notification “tweet.activity” with payload ⏎ ” {“messageid”:33,”rts”:0,”favs”:-1}” received from ⏎ server process with PID 73216. So we made seven inserts, and we have four notifications. This behavior might be surprising, yet it is fully documented on the PostgreSQL manual page for the NOTIFY command:
Why does PostgreSQL listen when the server is idle?
This means that as soon as a connection is established with PostgreSQL, the server can send messages to the client even when the client is idle. Messages that flow from the server to the connected client should be processed by the client. It could be that the server is being restarted, or an application message is being delivered.
How does the streaming protocol work in PostgreSQL?
The PostgreSQL protocol includes a streaming protocol with COPY and also implements asynchronous messages and notifications. This means that as soon as a connection is established with PostgreSQL, the server can send messages to the client even when the client is idle.