What is the function of the $sort stage in an aggregation pipeline?

The $sort stage in an aggregation pipeline is designed to organize the documents that are being processed. It sorts all input documents according to specified fields in ascending or descending order and ensures that the subsequent stages of the pipeline receive these documents in that sorted order. This ordering is crucial for operations that may depend on the sequence of documents, such as when performing calculations, grouping, or limiting the results.

When using the $sort stage, you can specify one or more fields by which to sort the documents, and you can control the sorting direction (either ascending or descending). This makes it a powerful tool for preparing and structuring data as it flows through the aggregation pipeline.

The other options pertain to distinct functionalities that do not align with what the $sort stage accomplishes, such as filtering documents or shuffling them, which is not the intent of the $sort operation.