Starting in 7.10, Elasticsearch supports an option to set case_insensitive: true on the wildcard search query. This works internally by rewriting the searches to regular expressions that match upper and lower case characters.

Options for how to expose this

a. Set this flag to be the default in all KQL wildcard searches, without changing the KQL grammar. This has some potential performance issues as described in a comment by @markharwood in the related issue about wildcard fields:

For example - if they support a *foo* style query in the KQL bar and assume, like normal whole-term based queries, that can be run across multiple fields then it may result in slow results or timeouts. Wildcard fields will be fast but hitting other fields which are keyword will involve an expensive linear scan.

b. Only set this flag by default when the user is running wildcard query on wildcard type fields. This would be the most performant option, but it would potentially be confusing to have two different behaviors.

c. Add something to the KQL grammar, like this request to add an UPPER() function to KQL. This could let users enable case insensitive queries as needed. I don't have a proposed grammar.

cc @elastic/kibana-app-arch @markharwood