MongoDB Merge Equivalent Collections

Question

I have two collections with same structure and want to merge them in aggregation result and query & sort over them after merging.

E.g.;

First collection:

{_id: "123", "name": "sercan"}

Second collection:

{_id: "456", "name": "hakan"}

What I want;

[{_id: "123", "name": "sercan"}, {_id: "456", "name": "hakan"}]

What I tried;

{"from":"secondCollection",pipeline: [],"as":"seconds"}
// result
{_id: "123", "name": "sercan", seconds: [{_id: "456", "name": "hakan"}]}

And the above trial, puts all documents into seconds if there're more documents in the second collection.

Thanks in advance

Answer 1

The one option I have used is $merge in MongoDB. It's basically merge one collection to another and create new output collection if it does not exist.

Reference:

• https://www.mongodb.com/docs/manual/reference/operator/aggregation/merge/