Is it possible to get single result in aggregate?

Is it possible to get a single result in an aggregate?

The answer is both YES and NO depending on your perspective and the specific requirements of your query.

NO, you cannot get a single result directly from an aggregate operation

By default, $aggregate returns a cursor that may contain multiple documents. Even if your query matches only one document, the result will still be a list (of length one in that case). To get a single document as the result, you need to use additional operations such as $limit or $group.

YES, you can get a single result by using additional operations

There are a few ways to get a single result from an aggregate operation:

1. Use the $limit operator:

db.collection.aggregate([
  { $match: { _id: "12345" } },
  { $limit: 1 }
])

This will return the first document that matches the query.

2. Use the $group operator:

db.collection.aggregate([
  { $match: { _id: "12345" } },
  { $group: { _id: null, result: { $first: "$$ROOT" } } }
])

This will group the results by _id (which will be null since we're not grouping by any field) and return the first document in the group.

3. Use the findOne() method:

db.collection.findOne({ _id: "12345" })

This will return the first document that matches the query.

Ultimately, the best approach for getting a single result from an aggregate operation will depend on the specific requirements of your query and the structure of your data.