cloudant groupby and count number of times a value appears - cloudant

Question

First time working with a nosql DB and having trouble writing a query that can look in my DB and for a key count the number of time it appears by another key.
For instance if my DB contains
{
"person": "user1",
"status": "good"
},
{
"person": "user1",
"status": "good"
},
{
"person": "user1",
"status": "bad"
},
{
"person": "user2",
"status": "good"
}
would like to know that person1 was good 2 and bad 1 and person2 was only good 1
in sql would do
select person, status, count(*)
from mydb
groupby person, status
or to get it by a user in the db
select person, status, count(*)
from mydb
groupby person, status
where person = "user1"

Answer 1

You can achieve this with Cloudant's MapReduce views and suitably chosen query parameters. I created a view where the map is
function (doc) {
emit([doc.person, doc.status], null);
}
and the reduce the built-in _count. That gives us an index where the key is a vector, and we can then group at different levels. Using groupby=true with group_level=2 gives us the desired result:
curl 'https://A.cloudant.com/D/_design/so/_view/by-status?groupby=true&group_level=2'
{
"rows": [
{
"key": [
"user1",
"bad"
],
"value": 1
},
{
"key": [
"user1",
"good"
],
"value": 2
},
{
"key": [
"user2",
"good"
],
"value": 1
}
]
}