Hi, As per documentation for default_field in query_string query (Ref: https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-query-string-query.html):
Defaults to the index.query.default_field index setting, which has a default value of *. The * value extracts all fields that are eligible to term queries and filters the metadata fields. All extracted fields are then combined to build a query if no prefix is specified.
And by this:
https://github.com/elastic/elasticsearch/blob/e0b3ea041671e7600e8a1b76491f91041940a386/server/src/main/java/org/elasticsearch/index/search/QueryParserHelper.java#L148
Does this mean that fields starting with _ are considered as metadata fields ?
Should Users not index fields starting with _ ?