Count number of values inside an array mongo PHP [duplicate]

Question

I need to get the total number of array elements that are present inside the products array . So far i have tried using the $size=>$products approach but since technically there are two arrays only the value i get is 2 but i want to count the inner elements as well so that the desired result comes out to be 3.

I know i need to use $unwind but i cant figure out the approach.

{  
   _id:2,
   card_pay:3998,
   count:4598,
   orders:2,
   products:[  
      [  
         {  
            product_id:{  
               $oid:"5c63d418ae1db123d8048276"
            },
            amount:2499,
            quantity:1,
            status:1
         },
         {  
            product_id:{  
               $oid:"5c46f7f329067970211471a0"
            },
            amount:200,
            quantity:2,
            status:1
         }
      ],
      [  
         {  
            product_id:{  
               $oid:"5c63d3afae1db123d8048273"
            },
            amount:1499,
            quantity:1,
            status:1
         }
      ]
   ]
}

EDIT 1: ['$project'=>[ 'number_of_products'=> ['$size'=> '$products']

So far i have tried this .

EDIT 2:

So far i have tried this .

[
	'$project'=>[
      'posts'=> [
         '$map'=> [
         'input'=> '$products',
         'as'=> 'products_inner',
         'in'=> [
               'Count'=>[
			   '$size'=> '$$products_inner'
         ]
   ]
 ],
						],

And i am getting the output

[
  {
    _id: 2,
    posts: [
      {
        Count: 2
      },
      {
        Count: 1
      }
    ]
  }
]

Now all i need to do is count the values to get 3 as the answer

matthPen · Accepted Answer · 2019-02-28 12:47:39Z

1

You were very close to the solution witm $map . Here's what you have to do : (feel free to translate this console query into your language implementation) :

 db.collection.aggregate([
      {
        $project: {
          totalPosts: {
            $sum: {
              $map: {
                input: "$products",
                as: "products_inner",
                in: {
                  $size: "$$products_inner"
                }
              }
            },

          }
        }
      },
    ])

Will result in :

[
  {
    "_id": 2,
    "totalPosts": 3
  }
]

answered Feb 28, 2019 at 12:47

matthPen

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