Collections由数组支持，在集合内随机查找内容时性能较好。
Collections are backed by arrays, which leads to good performance when looking up items randomly within a collection.
可以随机查找数据组，且可基于数据库中一个称为“架构”的结构中定义数据的方式检索相关数据。
Data groups can be found randomly, and associated data can be retrieved based on the way the data is defined to the database in a structure called a "schema."
和MapReduce相比，Percolator可以以低很多的延迟来处理数据，同时需要额外的资源来支持随机查找。
When compared to MapReduce, Percolator can process data with far lower latency, with an additional set of resources to support random lookups.
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