具有多个条件的 Mongo 3.6 聚合查找

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假设我有一个只有一个集合 data 的 Mongo DB.在这个集合中，我有以下文档:

Suppose I have a Mongo DB with only one collection data. In this collection, I have the following documents:

{ "type": "person", "value": { "id": 1, "name": "Person 1", "age": 10 } }, { "type": "person", "value": { "id": 2, "name": "Person 2", "age": 20 } }, { "type": "prescription", "value": { "drug": "Bromhexine", "patient": 2 } }, { "type": "prescription", "value": { "drug": "Aspirin", "patient": 1 } }

有了这些记录，我想在 "type": person 和 "type":处方 上的 value.id 文档之间进行 JOIN= value.patient.

With those records, I'd like to make a JOIN between documents with "type": person and "type": prescription on value.id = value.patient.

我已经尝试了以下阶段的聚合:

I've already tried an aggregation with the following stages:

{ "$match": { "type": "person" } }, { "$lookup": { "from": "data", "let": { "patient": "$value.id"}, "pipeline": [ { "$match": { "$expr": { "type": "prescription", "value.patient": "$$patient" } } } ], "as": "prescription" } }

但它会产生错误FieldPath 字段名称可能不包含'.'.我认为这是由于 "let": { "patient": "$value.id"}, 行.相反，如果我尝试使用双美元符号 ($$)(如 here 所示))，结果是错误Use of undefined variable: value.

But it produces an error FieldPath field names may not contain '.'. Which I believe is due to the "let": { "patient": "$value.id"}, line. If instead I try double dollar signs ($$) (as seen here), the result is the error Use of undefined variable: value.

知道如何进行这种聚合吗?

Any idea of how I can make this aggregation?

推荐答案

在 $lookup 阶段完成以下管道对象

Done with the following pipeline object inside the $lookup stage

"pipeline": [ { "$match": { "$expr": { "$and": [ { "$eq": [ "$type", "prescription" ] }, { "$eq": [ "$value.patient", "$$patient" ] } ] } } } ]