How to override rollback behavior in DIH

[Peter Keegan]

I have a custom data import handler that creates an ExternalFileField from
a source that is different from the main index. If the import fails (in my
case, a connection refused in URLDataSource), I don't want to roll back any
uncommitted changes to the main index. However, this seems to be the
default behavior. Is there a way to override the IndexWriter rollback?

Thanks,
Peter