I've created a background worker and I am using Postgresql-9.4. This bgworker handles the job queue dynamically and goes to sleep if there is no job to process within the next 1 hour.
Now, I want to have a mechanism to wake the bgworker up in case if someone adds a new job while the bgworker is in sleep mode. So to do it, I have created a trigger which initially removes the existing background worker and then registers a new one.
Don't do that.
Instead, set the background worker's process latch, which you can find in the PGPROC array. There are a variety of examples of how to set latches in the sources.
I am retrieving the pid from pg_Stat_activity. The maximum number of background worker that can run simultaneously is equal to 8. I think even if I call pg_terminate_backend the metadata of the background worker is not being deleted
Correct. Unless you register it as a dynamic bgworker with no automatic restart, it'll get restarted when it exits uncleanly.
Have the worker call proc_exit(0) if you want it not to be restarted.