[elasticsearch] sub aggregation의 개수 제한이 있을까?

elaticsearch의 aggreation는 깊이 제한(개수 제한) 없이 sub-aggregation을 구성할 수 있다. 

https://www.elastic.co/guide/en/elasticsearch/reference/1.x/search-aggregations.html

Bucketing aggregations can have sub-aggregations (bucketing or metric). The sub-aggregations will be computed for the buckets which their parent aggregation generates. There is no hard limit on the level/depth of nested aggregations (one can nest an aggregation under a "parent" aggregation, which is itself a sub-aggregation of another higher-level aggregation).