In below copy activity screen shot , i am trying to create a new column(PartitionKey) whose value is same as DocType column. I would also like to insert one string value along with Doctype value. something like concat("recoding",$.Doctype) as value of PartitionKey. I am unable to do so and would like to know if this is possible to do.
I want this because I get error for some items where DocType key is not present. and I would like to avoid that.
The error message i get is below and I am not sure for which item this error occurs as there are thousands of items getting copied.
ErrorCode=DuplicateColumnNotFound,'Type=Microsoft.DataTransfer.Common.Shared.HybridDeliveryException,Message=,Source=,''Type=Microsoft.DataTransfer.Common.Shared.HybridDeliveryException,Message=Column name '$.DocType' to be duplicated is not found in the source data. Please check the source column name

