mongodb php: count the number of field in a set of documents - php

Question

I am using codeigniter with mongodb library
https://github.com/intekhabrizvi/Codeigniter-mongo-library
below is my collection "users".
I want to count all the badges which has badge_slug = 100_club from users collection.
What I have tried is
$this->mongo_db->where(array('badges.badge_slug'=>"100_club"))->count('users');
but it only gives the number of users have 100_club no matter its more then one time.
{
"_id" : ObjectId("57b83ae9faa76bac338b4579"),
"displayname" : "test",
"email" : "test#gmail.com",
"badges" : [
{
"awarded_at" : ISODate("2015-04-21T05:52:06Z"),
"object_id" : "",
"badge_slug" : "100_club"
},
{
"awarded_at" : ISODate("2015-04-21T06:12:14Z"),
"object_id" : "",
"badge_slug" : "100_club"
},
{
"awarded_at" : ISODate("2015-04-21T07:09:55Z"),
"object_id" : "",
"badge_slug" : "reader"
}
]
}
{
"_id" : ObjectId("57b83ae9faa76bac338b457a"),
"displayname" : "test2",
"email" : "test2#gmail.com",
"badges" : [
{
"awarded_at" : ISODate("2015-04-21T06:44:20Z"),
"object_id" : "",
"badge_slug" : "100_club"
}
]
}
Can you please let me know how can I get the total number of 100_club occurred in the users collection.

Answer 1

The aggregation approach follows where you can use the $filter and $size operators to get the count per document and then group all the documents to get the total count. This approach doesn't require using the $unwind operator to flatten the badges array but works with MongoDB version 3.2 and greater:
mongo shell
var ops = [
{
"$project" {
"count": {
"$size": {
"$filter": {
"input": "$badges",
"as": "badge",
"cond": { "$eq": ["$$badge.badge_slug", "100_club"] }
}
}
}
}
},
{
"$group": {
"_id": null,
"total": { "$sum": "$count" }
}
}
];
db.users.aggregate(ops);
PHP
$ops = array(
array(
"$project" => array(
"count" => array(
"$size" => array(
"$filter" => array(
"input" => "$badges",
"as" => "badge",
"cond" => array("$eq" => => array("$$badge.badge_slug", "100_club") )
)
)
)
)
),
array(
"$group" => array(
"_id" => null,
"total" => array( "$sum" => "$count" )
)
)
);
$this->mongo_db->aggregate("users", $ops);
For an approach that uses the $unwind operator to flatten the badges array first before grouping, follow this example:
mongo shell
db.users.aggregate([
{ "$match": { "badges.badge_slug": "100_club" }
{ "$unwind": "$badges" },
{ "$match": { "badges.badge_slug": "100_club" },
{
"$group": {
"_id": null,
"total": { "$sum": 1 }
}
}
])