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I am creating a GUI that is dependent on information from MySQL table, what i want to be able to do is to display a message every time the table is updated with new data. I am not sure how to do this or even if it is possible. I have codes that retrieve the newest MySQL update but I don't know how to have a message every time new data comes into a table. Thanks!

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  • 1. do you control the source of the inserts?.. Could you expand it to inform your GUI to display a message?.. Say, by sending some message? 2. what is required latency of your message after table updates?.. is it okay for message to be displayed within, say, 1 second after update happens?.. Commented Jul 19, 2012 at 19:15

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Quite simple and straightforward solution will be just to poll the latest autoincrement id from your table, and compare it with what you've seen at the previous poll. If it is greater -- you have new data. This is called 'active polling', it's simple to implement and will suffice if you do this not too often. So you have to store the last id value somewhere in your GUI. And note that this stored value will reset when you restart your GUI application -- be sure to think what to do at the start of the GUI. Probably you will need to track only insertions that occur while GUI is running -- then, at the GUI startup you need just to poll and store current id value, and then poll peroidically and react on its changes.

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@spacediver gives some good advice about the active polling approach. I wanted to post some other options as well.

You could use some type of message passing to communcate notifications between clients. ZeroMQ, twisted, etc offer these features. One way to do it is have the updating client issue the message along with their successful database insert. Clients can all listen to a channel for notifications instead of always polling the db.

If you cant control adding an update message to the client doing the insertions, you could also look at this link for using a database trigger to call a script which would simply issue an update message to your messaging framework. It explains installing a UDF extension to allow you to run a sys_exec command in a trigger and call a simple script.

This way clients simply respond to a notification instead of all checking regularily.

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yep, message passing looks better, but waaaaay more cumbersome to setup and administer. I hope the author will be able to factor out the interaction code to switch the scheme to some message passing, when the time comes.
@spacediver: Agreed. You have to set up another layer to have the message passing, though if its a huge system it can be worth it. The polling option is good if the user doesn't need instant notification and can set the interval a bit longer.

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