Remove Unused Columns From The Data Flow

Consider the following scenario. You’ve been developing some SSIS packages, nicely making sure that all errors and warnings are gone from the Error List window. So the next step is to deploy the packages to the server and schedule them. After some days you decide to have a look at the sysssislog table and discover that it’s filled with OnWarning records!

Well, this is an extreme example of course. Careful developers would notice the warnings in either the Output window or the Progress tab while testing the package in the BIDS.

All these warnings are indicating that some columns in your data flows have become obsolete.  Here’s an example:

The output column “BKCustomerID” (13529) on output “OLE DB Source Output” (12088) and component “OLE_SRC MySource” (12077) is not subsequently used in the Data Flow task. Removing this unused output column can increase Data Flow task performance.

The problem with these warnings is not only that they slow down the transformation process but they obfuscate the SSIS log with thousands of records, making it difficult for you when you need to investigate an issue. And this is something that you really don’t want, especially when the business people are calling you to ask why the data is not up-to-date on the production servers.

If you ever wished that you’d see these warnings whilst developing the package instead of at runtime only, now’s your chance to make a change. Or better, to ask Microsoft to implement the change.

Follow this link to cast your vote on Connect!

Thank you Jamie for pointing this out.

Have fun!

Valentino.