Agile Central: Defect - Unable to query field: SalesForce Case ID

Document ID : KB000098238
Last Modified Date : 28/05/2018
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When querying the field: "SalesForce Case ID" on a Defect by WSAPI we are getting: 

Query Expression Operators    This attribute cannot be used in queries.

This is an out of the box field. What does this error mean?
For more info see:

On the Defect artifact you can find these two fields:
User-added image

User-added image

User-added image

The SalesForce Case ID is an internal attribute within Rally and can not be used in queries. As you see, it is used within the Defect's revision history. When trying to use it in queries you will result with a message "This attribute cannot be used in queries."

You do need to use the SalesForce Case Number field in your queries.