回调中的唯一计数

Question

我有一个用户列表，我正在尝试获取用户电子邮件地址中每个唯一域的结果及其总数。

所以，假设我有这 5 个用户：

+--------------------------------------+--------------------------------+-------------+------------+-------------+
| 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 |
+--------------------------------------+--------------------------------+-------------+------------+-------------+

运行完成查询后，我希望看到这个结果：

+-------+----------------+
| count | domain         |
+-------+----------------+
|  1    | jourrapide.com |
+-------+----------------+
|  2    | dayrep.com     |
+-------+----------------+
|  2    | rhyta.com      |
+-------+----------------+

我目前正在运行下面查询以获取唯一域，但是如果我尝试在其中运行 count()，它会在 300 秒后显着失败，我预计会发生，因为我有超过 5 个用户:)

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
  }
})

正如你想象的那样，它完美地 returns 这个结果：

+-------+----------------+
| count | domain         |
+-------+----------------+
|  ???  | jourrapide.com |
+-------+----------------+
|  ???  | dayrep.com     |
+-------+----------------+
|  ???  | rhyta.com      |
+-------+----------------+

我希望这是有道理的。如果您认为我走错了路，请随时提出任何其他建议。

提前致谢！

Answer 1

你不能 distinct() 到 count()。相反，你想要 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')
  };
});

回调中的唯一计数

Unique counts in a callback

rethinkdb