What Is Unwind Function

Definition. $unwind. Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element.

When should I use aggregate in MongoDB?

1. Aggregation pipelines.
2. Single purpose aggregation methods.
3. Map-reduce functions.

What is true about $unwind stages in aggregation framework?

What is true about $group stages in aggregation framework ? A. This is a filtering operation and thus this can reduce the amount of documents that are given as input to the next stage. … This is a filtering operation and thus this can reduce the amount of documents that are given as input to the next stage.