Will uploading wordpress xml again create duplicate content?

Hi,

I have a custom post type which I’m using as a Card database. I uploaded a XML file that imported all the cards as posts with different meta data. I added additional meta data to each of the cards and have the updated XML file.

I wanted to know if reuploaded the XML file will it create duplicate posts, and if not will it just ignore the new upload or will it add the new meta data that will be in the new XML upload file.

Thanks