add additional comments

lib/que/adapters/active_record_with_lock.rb

@@ -16,11 +16,14 @@ def checkout_activerecord_adapter(&block)
         end
 
         def lock_database_connection
+            if Thread.current[:db_connection]
+                return Thread.current[:db_connection] if Thread.current[:db_connection].active?
+            end
             # We are storing this in thread variable here to make sure
             # same connection is used to acquire and release the advisory locks.
             # Advisory lock will not be released if any other connection from the
             # pool tries to release the lock
-            Thread.current[:db_connection] ||= @lock_record.connection
+            Thread.current[:db_connection] = @lock_record.connection
         end
 
         def execute(command, params=[])
@@ -51,14 +54,19 @@ def lock_job_with_lock_database(queue, cursor)
 
         def cleanup!
             @job_connection_pool.release_connection
-            @lock_record.release_connection
+            @lock_record.remove_connection
         end
 
         def pg_try_advisory_lock?(job_id)
             lock_database_connection.execute("SELECT pg_try_advisory_lock(#{job_id})").try(:first)&.fetch('pg_try_advisory_lock')
         end
 
         def unlock_job(job_id)
+            # If for any reason the connection that is used to get this advisory lock
+            # is corrupted, the lock on this job_id would already be released when the 
+            # connection holding the lock goes bad.
+            # Now, if a new connection tries to release the non existing lock this would just no op
+            # by returning false and return a warning "WARNING:  you don't own a lock of type ExclusiveLock"
             lock_database_connection.execute("SELECT pg_advisory_unlock(#{job_id})")
         end
       end