When datatype is invalid in one row in the Row Identifier column the error message is incorrect.

[alaurenz]

Repro steps: use upsert or replace method to upload a CSV file where one value in the Row Identifier column is the wrong datatype (i.e. text in a number column)

Expected: Unknown number format 'X' (line X of file)

Actual: Cannot find column X...

[aynleslie]

I cannot reproduce this exactly. If I replace a numeric row identifier with "hi" and use a csv file that lacks a header row, I get back errors like:

Unknown number format 'id'. (line 2 of file)

If I give the header row, the job proceeds along fine despite the badly identified row.