Assume that you use an unsupported data type in the PolyBase query that's not part of the external table schema in SQL Server 2019. In this scenario, the XML query in PolyBase fails with an error message that resembles the following:
Msg 7320, Level 16, State 110 - Unknown type Xml at GetSqlTypeId
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server: