lookup is not working in laravel using MongoDB

Im using MongoDB with laravel and trying to get data using $lookup, but its not working. I have 2 collection, one is states with '_id','state_id','state_name' and another collection is category with '_id','name','description','state_id'. So with lookup im trying to get state_name from states Collection, Below is my query.

     $query=[                 ['$project'=>                  [                      "_id"=>1,                      "name" => 1,                      "description"=>1,                      "state_id"=>1,                      "data"=>1,                      "state_name"=>1, // trying to project this using lookup                  ]],                     ['$lookup' => [                   'from' => 'category',                    'localField' => 'state_id',                  'foreignField'  =>  'state_id',                  'as'  => 'states_docs',                 ]],                   [                  '$unwind'=> '$data'                 ],                  [                  '$group'=>[                      '_id'=>'$_id',                      'name'=> [ '$first'=> '$name' ],                      'description'=>['$first'=>'$description'],                      'state_id'=>['$first'=>'$state_id'],                      'data'=>['$first'=>'$data'],                      'state_name'=>['$first'=>'$state_name'],                  ]               ],            ];                      //query to database          $result = $collection->aggregate($query);          foreach($result as $row)          {                  $data[]=[                   '_id'=>$row->_id,                  'name' => $row->name,                  'description'=>$row->description,                  'state_id'=>$row->state_id,                  'state_name' => $row->state_name,//trying to get state_name using lookup                    ];           }  

Please help me to get state_name in this data array.

https://stackoverflow.com/questions/65785347/lookup-is-not-working-in-laravel-using-mongodb January 19, 2021 at 12:08PM