猫鼬-获取_id列表，而不是具有_id的对象数组 [英] Mongoose - Get list of _ids instead of array of objects with _id

问题描述

我想运行以下查询:

Group.find({program: {$in: [...]}}).lean().select('_id')

然后不返回以下信息:

[{_id: ...}, {_id: ...}, {_id: ...}, {_id: ...}]

但如下:

[..., ..., ..., ...] where ... represents an _id of a Group

当然，我可以只运行查询，然后遍历返回的组，但是如果可能的话，我想在查询中进行操作，因为这可能会更快.

Of course I could just run the query and then loop through the Groups I get back, but I would like to do it in the query if possible, because that's probably going to be faster.

谢谢你们！

推荐答案

Group.find({program: {$in: [...]}})
  .distinct('_id')

db.collection.distinct(字段，查询)

在单个集合中查找指定字段的不同值，并将结果返回到数组中.

Finds the distinct values for a specified field across a single collection and returns the results in an array.

了解详情.

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