Parent/child has been rewritten completely to reduce memory usage and to execute has_child and has_parent queries faster and more efficient. The _parent field uses doc values by default. The refactored and improved implementation is only active for indices created on or after version 2.0.parent/child는 memory 사용을 줄이고, has_child 와 has_parent query를 더 빨리, 더 효과적으로 실행하기 위해, 완전히 다시 작성되었다. _parent fiel..