How to do Relation Count with eager loading?

Question

Yii

In the first yii, everything was done quite simply, but in the second, a plug that leads to 250 requests on a normal page. And I would like to do everything without crutches.
there is relation:

public function getPostStatisticsCount()
    {
        return $this->hasMany(PostStatistics::className(), ['post_id' => 'id'])->count();
    }

There is a function call with eager loading

$mm =  Post::find()->with('postStatisticsCount')... ->all();

But eager loading doesn't work.
Similar behavior is described here - https://github.com/yiisoft/yii2/issues/2179 .
On the yii forum, I was advised to push the relation into the class constructor.
I would like an example of a solution with a constructor.

Answer 1

$customers = Customer::find()
    ->select([
        '{{customer}}.*', // select all customer fields
        'COUNT({{order}}.id) AS ordersCount' // calculate orders count
    ])
    ->joinWith('orders') // ensure table junction
    ->groupBy('{{customer}}.id') // group the result to ensure aggregation function works
    ->all();

I pulled it out from the sources ...
Something like this works in my application, although if possible, it is better to go from the opposite and search through the model PostStatisticsand group byPost