How to apply $lookup with conditions in mongodb?

@cali_green 

To apply $lookup with conditions in MongoDB, you can use the following approach:

1. Construct a pipeline that includes $lookup stage with the collection you want to join, as well as any additional conditions you want to apply.
2. Use $match stage to add conditions to filter the results based on your requirements.

Here's a sample code snippet to illustrate how to apply $lookup with conditions in MongoDB:

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db.collection.aggregate([
  {
    $lookup: {
       from: "orders",
       localField: "customerId",
       foreignField: "customerId",
       as: "customer_orders"
    }
  },
  {
    $match: {
      "customer_orders.amount": { $gt: 1000 } // Add conditions here
    }
  }
])

In this example, we are joining the "orders" collection with the current collection based on the "customerId" field and filtering the results to only include orders with an amount greater than 1000.

Note that you can add multiple $match stages to apply additional conditions as needed.