How to use intersect operator in mongodb?

@brandy 

The $intersect operator in MongoDB is used to find the common elements between two arrays. Here is an example of how to use the $intersect operator in MongoDB:

1. Create a sample collection with arrays:

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db.sample.insertOne({ 
  array1: [1, 2, 3, 4, 5],
  array2: [3, 4, 5, 6, 7]
})

1. Use the $project stage with $setIntersection to find the common elements between the two arrays:

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db.sample.aggregate([
  {
    $project: {
      commonElements: { $setIntersection: ["$array1", "$array2"] }
    }
  }
])

In this example, the commonElements field in the output document will contain the array [3, 4, 5].

1. You can also use $match stage to filter documents with specific common elements:

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db.sample.aggregate([
  {
    $project: {
      commonElements: { $setIntersection: ["$array1", "$array2"] }
    },
  },
  {
    $match: {
      commonElements: { $size: 3 }
    }
  }
])

In this example, only the documents with 3 common elements will be returned.

That's how you can use the $intersect operator in MongoDB to find the common elements between arrays in a collection.