I have a similar question regarding the removal of doc types as @smlbiobot 's post here With the removal of doc types, must I reindex all the indices that use a named type? . Do I have to reindex all the indices before I upgrade, or can I upgrade and simply update requests to call _doc type instead of custom type as ES will ignore custom type in indices?
My indices only have one custom doc type (not _doc) and are named in the format of <index_name>-YYYY-MM-DD (e.g., filebeat-2023-02-13). New documents will roll into a new index every day. I have updated index templates to use _doc type in preparation for the removal of doc types, so the new indices created after the day I updated the index template are indexing with _doc doc_type. However, the indices created before the template was updated still have custom doc_type. All indices were created in ES 6.x or ES 7.x (~OpenSearch1.3). Each of our indices has more than 23 million documents, so the reindex process is really time-consuming and involves a lot of manual labor. I would like to know if I had to reindex all the indices from a custom name doc type (e.g., doc, event, etc) to _doc type before the upgrade.
Any advice would be appreciated. Thank you!