Break by key on reduce function

Question

I'm using Cloudant (which is based on CouchDB) to store some data and want to create a reduce function to sum everything by key. I'm using the following mapping function:

function (doc) {
  emit(doc.name, 1);
}

Therefore, I'm receiving a json file like this:

{
    "total_rows": 3,
    "offset": 0,
    "rows": [
        {
            "id": "605b21a9c295ec9c03ae2a6aadeb1422",
            "key": "foo",
            "value": 1
        },
        {
            "id": "cb4258669082efeae9391288eb684339",
            "key": "foo",
            "value": 1
        },
        {
            "id": "f2e7e69d6a3d26fa3b8cad1f0c63ccc3",
            "key": "bar",
            "value": 1
        }
    ]
}

Therefore, for the _sum built-in function I was expecting something like:

{
    "rows": [
        {
            "key": "foo",
            "value": 2
        },
        {
            "key": "bar",
            "value": 1
        }
    ]
}

But I'm getting this:

{
    "rows": [
        {
            "key": null,
            "value": 3
        }
    ]
}

I was reading the Cloudant documentation and found that the _sum function:

Produces the sum of all values for a key, values must be numeric

But the result is not returning by key, but every value on my map.

Alexis Côté Alexis Côté · Accepted Answer · 2017-04-27T00:25:58

You forgot to set the reduce query parameters.

I used the same map function + _sum function.

URL : http://host:5984/db/_design/stack/_view/byname?reduce=true&group=true

Result :

{"rows":[
{"key":"bar","value":1},
{"key":"foo","value":2}
]}

Break by key on reduce function

1 Answers