来自 MongoDB 的随机记录 [英] Random record from MongoDB

问题描述

我希望从庞大的集合(1 亿条记录)中随机获取一条记录.

I am looking to get a random record from a huge collection (100 million records).

最快最有效的方法是什么?

What is the fastest and most efficient way to do so?

数据已经存在，并且没有可以生成随机数并获得随机行的字段.

The data is already there and there are no field in which I can generate a random number and obtain a random row.

推荐答案

从 MongoDB 3.2 版本开始，您可以使用 $sample 聚合管道操作符:

Starting with the 3.2 release of MongoDB, you can get N random docs from a collection using the $sample aggregation pipeline operator:

// Get one random document from the mycoll collection.
db.mycoll.aggregate([{ $sample: { size: 1 } }])

如果要从集合的过滤子集中选择随机文档，请在管道中添加 $match 阶段:

If you want to select the random document(s) from a filtered subset of the collection, prepend a $match stage to the pipeline:

// Get one random document matching {a: 10} from the mycoll collection.
db.mycoll.aggregate([
    { $match: { a: 10 } },
    { $sample: { size: 1 } }
])

如注释中所述，当size大于1时，返回的文档样本中可能存在重复.

As noted in the comments, when size is greater than 1, there may be duplicates in the returned document sample.

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