Can you combine specific and none-specific fields in mongodb find on embedded documents?

Question

I have embedded documents like

{ a: 
     { aa: { aaa: 1, bbb: 2, ccc: 3 },
       bb: { aaa: 1, bbb: 2, ccc: 3 },
       cc: { aaa: 1, bbb: 2, ccc: 3 }
     }
}

How can I write a field filter like:

find({}, { "a.*.aaa": 1 } )

* = aa, bb, cc

In mongodb documentation is no hint (see https://docs.mongodb.com/v3.2/tutorial/project-fields-from-query-results/)

score 1 · Accepted Answer · edited May 23 '17 at 12:08

This can be done if you are querying for value. But what you are trying is on the key. We have to give exact match on the key.

We can use $regex to match on value and not on the key.

Let us have a collection

db.collection.find();
{ "_id" : ObjectId("583eed6c911c8e111fb99bf4"), "name" : "a.aa.aaa" }
{ "_id" : ObjectId("583eed72911c8e111fb99bf5"), "name" : "a.bb.aaa" }
{ "_id" : ObjectId("583eed77911c8e111fb99bf6"), "name" : "a.bb.bbb" }
{ "_id" : ObjectId("583eed7b911c8e111fb99bf7"), "name" : "a.cc.bbb" }
{ "_id" : ObjectId("583eed7f911c8e111fb99bf8"), "name" : "a.cc.aaa" }
{ "_id" : ObjectId("583eed84911c8e111fb99bf9"), "name" : "a.cc.bbb" }
{ "_id" : ObjectId("583eed88911c8e111fb99bfa"), "name" : "a.cc.ccc" }
{ "_id" : ObjectId("583eed9a911c8e111fb99bfb"), "name" : "a.aa.ccc" }
{ "_id" : ObjectId("583eeda4911c8e111fb99bfc"), "name" : "a.aa.bbb" }
{ "_id" : ObjectId("583eedfd911c8e111fb99bfd"), "name" : "a.aa.abc" }
{ "_id" : ObjectId("583eee03911c8e111fb99bfe"), "name" : "a.bb.abc" }
{ "_id" : ObjectId("583eee06911c8e111fb99bff"), "name" : "a.cc.abc" }

Then the query using $regex is like

db.collection.find({name:{$regex: /a.*.aa*/}});

and the result of this query

{ "_id" : ObjectId("583eed6c911c8e111fb99bf4"), "name" : "a.aa.aaa" }
{ "_id" : ObjectId("583eed72911c8e111fb99bf5"), "name" : "a.bb.aaa" }
{ "_id" : ObjectId("583eed7f911c8e111fb99bf8"), "name" : "a.cc.aaa" }
{ "_id" : ObjectId("583eed9a911c8e111fb99bfb"), "name" : "a.aa.ccc" }
{ "_id" : ObjectId("583eeda4911c8e111fb99bfc"), "name" : "a.aa.bbb" }
{ "_id" : ObjectId("583eedfd911c8e111fb99bfd"), "name" : "a.aa.abc" }
{ "_id" : ObjectId("583eee03911c8e111fb99bfe"), "name" : "a.bb.abc" }
{ "_id" : ObjectId("583eee06911c8e111fb99bff"), "name" : "a.cc.abc" }

Pls refer: Mongodb - regex match of keys for subobjects

Hope it Helps!

Can you combine specific and none-specific fields in mongodb find on embedded documents?

1 Answers1