PostgreSQL Notify/Listen Tips

Getting Started
1

Hey all, I’m working on a database application and am starting to look into the PostgresqlDatabase Notify and Listen function. I’m having trouble wrapping my head around how exactly to use it. I am looking to have multiple users connected to the database and have the database push changes to the clients whenever there is a change. Here is what I have figured out so far. I need to create a trigger in postgres that sends a notification to clients whenever a change is made to a table.( I am still trying to figure out the specifics of how to make that happen, but I am fairly confident I can figure that part out.) On the client side I am a little more confused on what the best method is. It is sounding like I need to create some sort of timer that continually checks for a new notification and reacts accordingly if it does. But it seems like there should be a better way.
This is my first time working with Postgres and could really use any suggestions you can give me.

Thanks

2

Have you looked at the ListenNotify examples that come with Xojo?

Examples/Database/PostgreSQL/ListenAndNotify

These examples run on the client, not the server. But they allow any client to listen for notifications sent from any other client. There may be a way for the server to also send a notification, but I’m not familiar with that.

3

Be aware that Xojo does not have support for the payload parameter of Notify/Listen.
That means that you can only send a notification to all clients that listens to the same channel but you can’t pass any variable data to the listeners.

4

A rule could be created that would send a notification when a table is updated.