엘라스틱서치 조인 가이드 문서 링크 https://www.elastic.co/guide/en/elasticsearch/reference/current/parent-join.html#parent-join 엘라스틱서치는 Parent-join이라는 것을 제공함. The join data type is a special field that creates parent/child relation within documents of the same index. The relations section defines a set of possible relations within the documents, each relation being a parent name and a child name. `join` 타입은 동일..