We have time-based data in Elasticsearch cluster: one index per month and use alias to join them. So the user only need to search on the index alias.
In the past when creating the index for each month, we didn't specify the _routing parameter. Now we realized the search performance issue and plan to use a customized _routing parameter for new index to be created going forward.
If we do this, the alias will include both indices with & without _routing parameter. Can we add _routing parameter to the Search API in this case? Will the Search return the correct result?
I don't think we can re-create the old index with _routing parameter because they're very large.