Welcome Back! Last time on Intro to Aggregations, we explored the basic concepts of aggregations and how to start using them. We toyed with simple bucket and metric aggregations, which gave us simple analytics.지난 번에 Intro to Aggregations에서, aggregation의 기본 개념과 사용방법을 살펴보았다. 간단한 bucket과 metric을 다루었는데, 이는 간단한 analytic을 제공했다.Today, we are going to learn about sub-aggregations. The most powerful feat..