https://www.elastic.co/search-labs/blog/esql-unmapped-fields-deep-dive
ES|QL unmapped fields: Query missing data without reindexing | Elasticsearch Labs
ES|QL unmapped fields stop the Unknown column error. Use LOAD to read values from _source or NULLIFY to return nulls. GA in Elasticsearch 9.5.
unmapped fieldsmissing dataelasticsearch labsquerywithout