Update by query after mapping change

Elastic Stack Elasticsearch
1

Hi,

In case I have a daily index and want to add a new field without waiting for the new index that would re-read the mapping template, I can use the Update mapping API. What I'm not 100% sure is that I would only need to use Update By Query API when I have documents that I want to update with the new field. To put this another way:
If I don't want to update indexed documents in the target index, only have the newly indexed ones picking up the mapping change (new field), I don't need to run an update, right?

Thanks!

2

Correct! When you add a new field via update mapping API, this will be only applied for newly indexed documents, old documents won't be affected in any way.