Capture TSQL when Missing_Join_Predicate event occurs

Question

I am configuring Event Notifications on a Service Broker Queue to log when various performance related events occur. One of these is Missing_Join_Predicate.

The XML payload of this event holds nothing useful for me to identify the cause (TSQL, query plan, objectid(s) etc) so in the procedure to process the queue I am trying to use the TransactionID to query dm_exec_requests and dm_exec_query_plan to get the query plan and the TSQL where the dm_exec_requests.transactionid is the TransactionID from the event.

The code catches no data.

Removing the filter from the query (ie collecting all rows from dm_exec_requests and dm_exec_query_plan) shows there are records returned but none for the TransactionID in question.

Is what I am trying to do possible? Where am I going wrong?!

Answer 1

The trace based event notifications, like MISSING_JOIN_PREDICATE, are just a verbatim translation of the corresponding trace event (Missing Join Predicate Event Class) and carry exactly the same info. For this particular event there's basically no useful info whatsoever, the <TransactionID> is the xact id that triggered the event and, by the time you dequeue it and process the notification message, the transaction is most likely finished and gone (yay for asynchronous queued based processing).

When using the original trace error event, eg. with Profiler, you could also enable SQL:BatchCompleted, filter appropriately and then catch the JOIN culprit in the act. But with Event Notifications I don't see any feasible way to automate the process to the point at which you can pinpoint the problem query and application. With EN you can, at best, raise the awareness of the problem, show the client that cause it (the app), and then use other means (eg. code inspection) to actually hunt down the problem root cause.

Unfortunately you'll discover that there are more event notification events that suffer from similar problem(s).