Mongodb group operation example in PHP

Following the previous article, this article mainly talks about the group function of mongodb, which is quite powerful. It is quite complicated to use find(), skip(), distinct(), etc.

Test data:

> db.fruit.find();  
{ "_id" : 1, "category" : "fruit", "name" : "apple" }  
{ "_id" : 2, "category" : "fruit", "name" : "peach" }  
{ "_id" : 3, "category" : "fruit", "name" : "banana" }  
{ "_id" : 4, "category" : "veggie", "name" : "corn" }  
{ "_id" : 5, "category" : "veggie", "name" : "broccoli" }

1. Group according to category

> db.fruit.group(  
       {  
         key: { category: 1},  
         reduce: function(obj, prev) {  
                     prev.items.push(obj.name);  
                 },  
         initial: { items : [] }  
       }  
    );  
[  
        {  
                "category" : "fruit",  
                "items" : [  
                        "apple",  
                        "peach",  
                        "banana"  
                ]  
        },  
        {  
                "category" : "veggie",  
                "items" : [  
                        "corn",  
                        "broccoli"  
                ]  
        }  
]

php code is as follows:

$keys = array("category" => 1);  
$initial = array("items" => array());  
$reduce = "function (obj, prev) { prev.items.push(obj.name); }";  
$g = $collection->group($keys, $initial, $reduce);  
  
print_r($g);   //结果如下。  
  
Array  
(  
    [retval] => Array  
        (  
            [0] => Array  
                (  
                    [category] => fruit  
                    [items] => Array  
                        (  
                            [0] => apple  
                            [1] => peach  
                            [2] => banana  
                        )  
  
                )  
  
            [1] => Array  
                (  
                    [category] => veggie  
                    [items] => Array  
                        (  
                            [0] => corn  
                            [1] => broccoli  
                        )  
  
                )  
  
        )  
  
    [count] => 5  
    [keys] => 2  
    [ok] => 1  
)

2. Group according to category and count

> db.fruit.group(  
           {  
             key: { category: 1},  
             cond: { _id: { $gt: 2 } },  
             reduce: function(obj, prev) {  
                prev.items.push(obj.name);  
                prev.count++;  
             },  
             initial: { items : [] ,count:0}  
           }  
        );  
[  
    {  
        "category" : "fruit",  
        "items" : [  
            "banana"  
        ],  
        "count" : 1  
    },  
    {  
        "category" : "veggie",  
        "items" : [  
            "corn",  
            "broccoli"  
        ],  
        "count" : 2  
    }  
]

php code as follows:

$keys = array("category" => 1);  
$initial = array("items" => array(),'count'=>0);  
$reduce = "function (obj, prev) { " .  
              "prev.items.push(obj.name); " .  
              "prev.count++;" .  
          "}";  
$condition = array('condition' => array("_id" => array( '$gt' => 2)));  
$g = $collection->group($keys, $initial, $reduce, $condition);  
  
print_r($g);   //结果如下。  
  
Array  
(  
    [retval] => Array  
        (  
            [0] => Array  
                (  
                    [category] => fruit  
                    [items] => Array  
                        (  
                            [0] => banana  
                        )  
  
                    [count] => 1  
                )  
  
            [1] => Array  
                (  
                    [category] => veggie  
                    [items] => Array  
                        (  
                            [0] => corn  
                            [1] => broccoli  
                        )  
  
                    [count] => 2  
                )  
        )  
  
    [count] => 3  
    [keys] => 2  
    [ok] => 1  
)

3. Use aggregate group function, It’s also quite powerful

> db.fruit.aggregate([  
                     { $match: { _id: {$gt:0} } },  
                     { $group: { _id: "$category", count: { $sum: 1 } } },  
                     { $sort: { count: -1 } }  
                   ]);  
{ "_id" : "fruit", "count" : 3 }  
{ "_id" : "veggie", "count" : 2 }

The PHP code is as follows:

$cond = array(  
    array(  
        '$match' => array('_id' => array('$gt' => 0)),  
    ),  
    array(  
        '$group' => array(  
            '_id' => '$category',  
           'count' => array('$sum' => 1),  
        ),  
    ),  
    array(  
        '$sort' => array("count" => -1),  
    ),  
);  
$result = $collection->aggregate($cond);  
print_r($result);    //结果如下：  
  
Array  
(  
    [result] => Array  
        (  
            [0] => Array  
                (  
                    [_id] => fruit  
                    [count] => 3  
                )  
  
            [1] => Array  
                (  
                    [_id] => veggie  
                    [count] => 2  
                )  
  
        )  
  
    [ok] => 1  
)

Mongodb has many select operations. Here, I only talk about some commonly used functions.

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