How to group records by a field in mongoose?

@gilbert 

To group records by a field in Mongoose, you can use the aggregate function provided by Mongoose. Here is an example of how you can group records by a specific field:

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// Assume you have a Mongoose model called 'User' with a field 'age'

User.aggregate([
  { 
    $group: {
      _id: '$age',
      count: { $sum: 1 }
    }
  }
], function(err, result) {
  if (err) {
    console.error(err);
  } else {
    console.log(result);
  }
});

In this example, we are using the aggregate function to group records from the 'User' collection by the 'age' field. The $group stage is used to group the documents by the 'age' field and then calculate the count of each group using the $sum accumulator. The result will be an array of objects where each object contains the _id (the age) and the count of records with that age.

You can customize the grouping logic based on your specific requirements by adding more stages to the aggregate pipeline.