Unique counts in a callback - rethinkdb

Question

I have a list of users, and I'm trying to get the result of each unique domain in users' email addresses and their totals.
So, let's say I have these 5 users:
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| id | email | firstname | lastname | something |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 00c0f0db-87d0-45b2-8ed2-aa94d1e3e659 | shane.conte#jourrapide.com | Shane | Conte | iew9anap0L |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 0114360a-3ef8-49d6-8c51-02392bc51e10 | michelle.guitierrez#dayrep.com | Michelle | Guitierrez | eeNgiev3foh |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 00e8e2f2-2130-4f65-8914-b93d5b029d75 | terri.hebert#rhyta.com | Terri | Hebert | vahMoKiuCh0 |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 00e1578b-cf6d-46b8-92e3-2388a80105f7 | richard.copeland#dayrep.com | Richard | Copeland | Iem4mohng |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 00f1be34-d60e-4b2f-b3ae-610c67151f2d | elsie.fuhrman#rhyta.com | Elsie | Fuhrman | aPie6piD6ae |
+--------------------------------------+--------------------------------+-------------+------------+-------------+
After running the query, I'd like to see this result:
+-------+----------------+
| count | domain |
+-------+----------------+
| 1 | jourrapide.com |
+-------+----------------+
| 2 | dayrep.com |
+-------+----------------+
| 2 | rhyta.com |
+-------+----------------+
I'm currently running this query below to get the unique domains but if I try to run count() in it, it dramatically fails after 300 seconds, which I expect to happen since I have A LOT more than 5 users :)
r.db('helloworld').table('users').pluck('email').map(function(user) {
return user('email').split('#').nth(1).downcase()
}).distinct().map(function(domain) {
return {
count: '???', // <--- this is where I need help
domain: domain
}
})
And as you can imagine, it perfectly returns this result:
+-------+----------------+
| count | domain |
+-------+----------------+
| ??? | jourrapide.com |
+-------+----------------+
| ??? | dayrep.com |
+-------+----------------+
| ??? | rhyta.com |
+-------+----------------+
I hope this makes sense. If you think I'm on a wrong path, feel free to suggest any other way.
Thanks in advance!

Answer 1

You can't distinct() to count(). Instead you want to group():
r.db('helloworld').table('users').pluck('email').map(function(user) {
// wrap the result in an object for grouping purposes
return { domain: user('email').split('#').nth(1).downcase() };
})
// this groups all domains together in a [{ group, reduction }] list of objects
.group('domain')
// after group(), calls are scoped to each reduction: count each one
.count()
// let's ungroup to scope the following calls to the whole sequence
.ungroup()
// let's be compliant with the format you expect
.map(function(doc) {
return {
domain: doc('group'),
count: doc('reduction')
};
});