Use _source to reindex data after a mapping update

[tcucchietti]

I've not found issues related to this topic but sorry if it's the case.

If the _source is enabled in a mapping, a nice feature would be to be able to add a parameter (e.g. reindex) in PUT mapping request to trigger the data automatic reindexing, based on the _source value. A wait_for_completion flag could be added too.

Something like this would be handy :
PUT index/type/_mapping?reindex&wait_for_completion=true

[clintongormley]

Hi @tcucchietti

You can't change existing mappings, so we wouldn't be able to reindex into the same index, but the ability to reindex from source into a new index with new mappings is definitely on the roadmap (#492). It is currently blocked by #6914, #6069, and #1242, but we are working on all of these.