Getting total count of mapped/reduced records in CouchDB

Question

The data in couch has a record for each contact type as follows.

[{
  "_id":"1"
  "contact_type":"AA"
  "contact_email" : "userA@domain.com"
},{
  "_id":"2"
  "contact_type":"BB"
  "contact_email" : "userA@domain.com"
},{
  "_id":"3"
  "contact_type":"CC"
  "contact_email" : "userA@domain.com"
},{
  "_id":"4"
  "contact_type":"AA"
  "contact_email" : "userB@domain.com"
},
{
  "_id":"5"
  "contact_type":"BB"
  "contact_email" : "userB@domain.com"
}]

Records 1,2,3 represent contact with the email userA@domain.com while records 4 and 5 represent contact with an email userB@domain.com.

My task is to build a query to get the total amount of unique contacts (2 in this case) but I am not sure how this can be achieved.

Currently, I have a map function with _count reduce

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

which returns

{
  "rows":
    {
      "key" : "userA@domain.com",
      "value" : 3
    },
    {
      "key" : "userA@domain.com",
      "value" : 2
    }
}

However, what I need is the total amount of those records above, i.e. something like

{
  "total" : 2
}

(Note: the database is large so looping through the mapped/reduced view to count the records is not an option)

score 0 · Answer 1 · answered Feb 06 '18 at 05:53

0

Set the reduce function to _count and it should do what you want.

In your case you can also use _sum.

answered Feb 06 '18 at 05:53

xpqz

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score 0 · Accepted Answer · answered Feb 06 '18 at 09:02

Yo can use the approach described in this post

1.- Define a view as you described in your question (i.e. named "emails")

2.- Define a list function (in my example named "count")

function(head,req){
 var count = 0;
 while(getRow()) count++;
 return JSON.stringify({total: count});
}

Assuming your design doc is named "users", you can transform the view result using the list function with this URL.

http://.../db/_design/users/_list/count/emails?group=true

You should get the distinct value count as the result.

Getting total count of mapped/reduced records in CouchDB

2 Answers2