【问题】

Is there a way to use the $map operator in a regular Mongo document query (or aggregate \$match which I believe is the same thing).

What I’m trying to do is thus: Given an set of sets, return the document if any of the sets is a subset of a parameter.

Example:

Let’s say I have three documents:
{x : [ [“A”,“B”] ] }
{x : [ [“A”, “D”] ] }
{x : [ [“A”,“B”], [“A”,“D”] ] }
and I have an array
auths = [“A”,“B”,“C”]

I want to run a query where I get back the first and third documents because both contain the set [“A”,“B”] which is a subset of auths, but not the second document because its only set contains D which is not in the set of auths

If I were doing this in a $redact pipeline I could do this with something along the lines of:

{“$anyElementTrue” : {
“$map” : {
“input”: “$x”,
“as”: “s”,
“in”: {“$setIsSubset”: [“$$s”, auths] }
}
}}

but when I try to run this as a query I get

BadValue unknown top level operator: $anyElementTrue

【回答】

直接使用 Mongodb 的 API 应该可以实现这个需求，但会比较繁琐，也可以考虑用 SPL 解决：

A2：

A3：对照序列

A4：对照 A2 每条记录的 au 是不是 A3 的子集，如果是就查出来