MongoDB Aggregation Attribute Pattern Pipeline/Query

Question

I have Attribute Patterned (https://www.mongodb.com/blog/post/building-with-patterns-the-attribute-pattern) field that looks like this:

"cmr_diag": [{
        "name": "shd?",
        "value": {
            "$numberDouble": "1"
        }
    }, {
        "name": "ischemic_hd",
        "value": {
            "$numberDouble": "1"
        }
    }, {
        "name": "non-ischemic_dcmp",
        "value": {
            "$numberDouble": "1"
        }
    }, {
        "name": "myocarditis",
        "value": {
            "$numberDouble": "0"
        }
    }, {
        "name": "hcm",
        "value": {
            "$numberDouble": "0"
        }
    }, {
        "name": "amyloidosis",
        "value": {
            "$numberDouble": "0"
        }
    }, {
        "name": "toxic_cmp",
        "value": {
            "$numberDouble": "1"
        }
      .
      .
      .

I'd like to create an aggregation pipeline that finds all patients with ONLY ischemic_hd, while all other possible illnesses are 0. I am not sure how to create this query however?

Can you add to the post an example of exactly what you need for the end result? — Rfroes87
– Rfroes87, Commented Aug 28, 2020 at 23:32

Joe · Accepted Answer · 2020-08-29 00:22:11Z

1

You can use $elemMatch to identify patients with a specific attribute.

If you want to exclude everything else, use $reduce to sum up the value of all of the attributes, and match where count = 1.

db.collection.aggregate([
   {$match: {
       cmr_diag: {
           $elemMatch: {
                  name: "ischemic_hd",
                  value: { "$numberDouble": "1" }
           }
       }
   }},
   {$addFields: {
       diagcount: {
          $reduce: {
              input: "$cmr_diag",
              initialValue: 0,
              in: {$sum: ["$$value","$$this.value.$numberDouble"]}
          }
       }
    }},
    {$match: { diagcount: 1}}
])

answered Aug 29, 2020 at 0:22

Joe

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