Dfs_query_then_fetch search type across multiple indexes

Elastic Stack Elasticsearch
1

Can some please tell me if using dfs_query_then_fetch search type across multiple indexes the term frequencies are calculated across indexes or per index basis ? Is it possible to sort the result by term frequencies for a search query across multiple indices ?

For example if we have the following indices with the following index users

Index A
John Smith
Dan Smith
Rachel Smith
Sam Smith

Index B
Steve Smith
Jane Doe
Ryan Johnson

And we do a prefix query for Smi* it would have a higher score for the match in index B then in index A as the term is less frequent?

Thanks

2

term frequencies are calculated across the set of shards in the search request no matter which index they belong to.