# 3.6.2.桶聚合(Bucket Aggregations)

Bucket aggregations 不像 metrics aggregations 那样计算指标，恰恰相反，它创建文档的buckets，每个buckets与标准（取决于聚合类型）相关联，它决定了当前上下文中的文档是否会“falls”到它。换句话说，bucket可以有效地定义文档集合。除了buckets本身，bucket集合还计算并返回“落入”每个bucket的文档数量。

与度量聚合相比，Bucket聚合可以保存子聚合，这些子聚合将针对由其“父”bucket聚合创建的bucket进行聚合。

有不同的bucket聚合器，每个具有不同的“bucketing”策略,一些定义一个单独的bucket，一些定义多个bucket的固定数量，另一些定义在聚合过程中动态创建bucket.


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