Re: Witango-Talk: Select 1 From xxx where 1=0

[Dave Machin]

Is it unusual that our production server doesn't issue the heartbeat query before each DB action?   On our development machine, I wrote a .taf application that issued an identical DB action 20 times (just copied and pasted the same DBMS action over and over).  In SQL profiler, when that application is executed, I see the heartbeat and then the query repeated 20 times in pairs as expected. But on our production server, we often see cases where there is no heartbeat query before a DBMS action.  Sometimes we see two or three DB actions execute before we see another heartbeat query.   The reason I ask is that we're definitely having trouble with WiTango either reading or writing to the wrong datasource occasionally, in the middle of a request.  We're trying to log all the evidence, but we had two cases today in production where two identical DBMS actions, executed one after the other, with no steps in-between, using <@var user$odbc> as the data source name, against the same data source returned different results.  In SQL profiler, we saw only one of the two queries on the database we expected, and the other ran against a different server entirely.   I can provide you with logs if you like.   ----- Original Message ----- From: Customer Support To: witango-talk@witango.com Sent: Tuesday, January 24, 2006 4:18 PM Subject: Re: Witango-Talk: Select 1 From xxx where 1=0 Dave, select 1 from TABLENAME where 1=0 is the heartbeat query.  In 5.5 it should run with the execution of each db based action.  It selects no rows, returns no rows and the result set is not retrieved so it does not affect performance and ensures the connection is established.  The reason for running it with each db action is that if the db goes down during the execution of a taf and fails over to another db server the taf will continue to work.  If you are using directDBMS actions then the heartbeat will be run once before your SQL is sent to the server. Witango Support  On 25/01/2006, at 8:46 AM, Dave Machin wrote: We're still having trouble with WiTango 5.5.009 reading or writing from the wrong data source.   In trying to figure out it, we've come up with a question.   We're running MS-SQL profiler to see all the database queries issued by WiTango.  We see one like this:   "select 1 from AgentIdToName where 1=0"   which happens before every database query in our .taf application.  We're assuming this is to check that the data source is still alive, in fact if we rename the AgentIdToName table in the middle of an execution, WiTango makes a new DB connection.  We also saw this in WiTango 5.0, although I seem to remember it only happening once at the beginning of a page request, not once for each query in the request.   Anyhow, here's our question:   On our development machine we see this keep alive query before each query executed, but on our production machine it seems to happen intermittently.  Some page requests have the keep alive before each query, some only have it every few queries.   Does anyone know if this is normal? ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf ________________________________________________________________________ TO UNSUBSCRIBE: Go to http://www.witango.com/developer/maillist.taf