I have nested json documents with about 4000 fields. To change the field type, I understand I have to reindex with a new index and updated mapping. But what if i want to change like 2500 fields? is there an alternative way to do this as opposed to manually creating a new mapping? updating 2500 fields seems tiring!
You will need to craete a new index template with updated mapping. With that number of fields it may be worthwhile creating a script.
To add to this, unfortunately there's nothing in the stack that can make this easy sorry to say.