Bulk add new field to all docs at once

[DmitryKey]

User story: http://stackoverflow.com/questions/39258828/adding-a-new-field-to-all-existing-documents-in-an-index

If link does not open:

I am using Luke, to add a new field to all existing documents in the index. I can easily do this for 1 document by using the "Reconstruct and Edit" option. However, I want to do this for all document, in one go. Right now, I have to do this one by one. There are 2000 Documents in the index. This would take a lot of time.