MongoDB count（）在php中是不同的

Question

I am wondering how to count the number of results of this simple mongodb query, using php.

<?php

//connection to mongodb

  $collection = new MongoCollection($db, 'User');

  $retval = $collection->distinct("age");

    var_dump($retval);
?>

How can i count how many results are into $retval variable?

Answer 1

Soory , to know how many result are in $retval its simple. Just write this:

echo count($retval);

---

My solution returns the count of child for one item distincted. Not the count of simple distinct collection ^^

For example if you have these data:

Age:  |  User:
--------------
{ "age":"20", "name":"David" }, 
{ "age":"20", "name":"Goerge" }, 
{ "age":"22", "name":"tiffany" }

My solution return an array and when you each this array such as:

foreach ($retval as $row) 
       echo($row['age'] . ': ' . $row['count'] . "\n");

Data returned:

20 : 2
22 : 1

Answer 2

The new Aggregation framework is going to make this easy: http://php.net/manual/en/mongocollection.aggregate.php

$project = array('$project'=> array("age"=>1)); //pick only the age field
$group = array('$group'=>array("_id"=>'$age')); //group by age field
$count = array('$group'=>array("_id"=>null,"count"=>array('$sum'=>1))); //count distinct    
$result = $collection->aggregate(array($project,$group,$count));
echo $result['result'][0]['count']; 

Answer 3

The PHP documentation for MongoDB describe how count in a getting collection: http://www.php.net/manual/en/mongocollection.count.php

For have the count over distinct result, you can create a map-reduce in group collecting such as this example:

<?php
$retval = $collection->group(
    array('age' => true), // field(s) to group by
    array('count' => 0), 
    new MongoCode('function(doc, prev) { prev.count += 1 }'), 
    array(null) // condition
    );
?>

The

new MongoCode(..)

function takes the current document and the aggregation to this point and does the aggregation. And finaly you can get the count:

print($retval["count"]);

Answer 4

$collection = new MongoCollection($db, 'contacts');  

$keys = array("Department" => 1);

// set intial values
$initial = array("count" => 0);

// JavaScript function to perform
$reduce = "function (obj, prev) { prev.count++; }";


// only use documents where the "state" field is ar

$condition = array('condition' => array("State" => 'AR'));

$results = $collection->group($keys, $initial, $reduce, $condition);

foreach ($results['retval'] as $key => $value) {
    echo 'Contacts in state AR with department '.$value['Department'] . ' are:'. $value['count'];
    echo '<br />';
}