We're running an optimize on a delta table with a VARIANT column that has a NOT NULL constraint.

Now, there are no NULL entries in this column. And yet, OPTIMIZE gives this error:

[DELTA_NOT_NULL_CONSTRAINT_VIOLATED] NOT NULL constraint violated for column: body.

What gives? There is in fact also no is_variant_null matches either. Could it be that the NOT NULL constraint is violated in some earlier transaction?

I am not able to drop the constraint because this is a streaming table.