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  1. Core Server
  2. SERVER-44355

Add $some array query operator



    • Type: New Feature
    • Status: Open
    • Priority: Major - P3
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: Backlog
    • Component/s: Querying
    • Labels:


      Using the $in and $all operators to query array fields cover a lot of ground, but when you want query for documents where the array holds at least 4 values, or exactly 8, then MongoDB is missing a useful operator.

      Let’s take a simple example. You have a collection of Customers, and each customer document has a purchasedProducts field, which is an array of ObjectId’s (references to all products the customer have purchased). Now, for a marketing campaign you want to find all your customers who have purchased at least 3 out of a set of 10 selected products, in order to send a message to these customers.

      In this scenario, the $in operator won’t do, because it would give you all customers who have purchased at least one of the products. The $all operator won’t work either, because it would only give you the customers who have purchased all 10 products in the set. In this scenario a $some operator would come in handy.

      As a suggestion, the $some operator could take an array with two items - the first item being an array of values to match against and the second item being an object declaring the condition for a match.

       * Example of a $some operator where the document would match if purchasedDocuments 
       * contain at least two of the three provided ObjectIds
        purchasedProducts: {
          $some: [[ObjectId('ID1'), ObjectId('ID2'), ObjectId('ID3')], { $gte: 2 }]

      Using an aggregation pipeline we get access to the tools we need to create the equivalent of a $some operator, as I've outlined in this Medium story but it gets quite verbose and it would be really convenient to have it available as regular query operator.


          Issue Links



              backlog-server-query Backlog - Query Team
              christofer@markethype.io Christofer Eliasson
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