invalid operator '$last' when grouping

[george-viaud]

Trying to do the following operation:

$query = new Lead;
$query->select('_id','first_name','last_name', 'email', 'created_at')
		->groupby('email')
		->where('created_at', '>=', $startDate)
		->where('created_at', '<', $endDate);

and then chunking because results are huge:

$chunkSize = 5000;
	
$query->chunk($chunkSize, function($leads) use(&$postFields)
	{
		Log::info("Processing chunk...");
		foreach($leads as $iLead => $lead)
		{
			// ... Do stuff with lead here ...
		}
	}
Log::info("Query Complete!");

Getting the following error

RuntimeException in Aggregate.php line 168: invalid operator '$last'
 in Aggregate.php line 168
at Server->executeCommand('mission_control', object(Command), object(ReadPreference)) in Aggregate.php line 168
at Aggregate->execute(object(Server)) in Collection.php line 191
at Collection->aggregate(array(array('$match' => array('$and' => array(array('created_at' => array('$gte' => object(UTCDateTime))), array('created_at' => array('$lt' => object(UTCDateTime)))))), array('$group' => array('_id' => array('$last' => '$_id'), 'email' => array('$last' => '$email'), 'first_name' => array('$last' => '$first_name'), 'last_name' => array('$last' => '$last_name'), 'created_at' => array('$last' => '$created_at'))), array('$limit' => '5000'), array('$project' => array('_id' => '1', 'first_name' => '1', 'last_name' => '1', 'email' => '1', 'created_at' => '1'))), array('typeMap' => array('root' => 'array', 'document' => 'array')))
at call_user_func_array(array(object(Collection), 'aggregate'), array(array(array('$match' => array('$and' => array(array('created_at' => array('$gte' => object(UTCDateTime))), array('created_at' => array('$lt' => object(UTCDateTime)))))), array('$group' => array('_id' => array('$last' => '$_id'), 'email' => array('$last' => '$email'), 'first_name' => array('$last' => '$first_name'), 'last_name' => array('$last' => '$last_name'), 'created_at' => array('$last' => '$created_at'))), array('$limit' => '5000'), array('$project' => array('_id' => '1', 'first_name' => '1', 'last_name' => '1', 'email' => '1', 'created_at' => '1'))), array('typeMap' => array('root' => 'array', 'document' => 'array')))) in Collection.php line 42
at Collection->__call('aggregate', array(array(array('$match' => array('$and' => array(array('created_at' => array('$gte' => object(UTCDateTime))), array('created_at' => array('$lt' => object(UTCDateTime)))))), array('$group' => array('_id' => array('$last' => '$_id'), 'email' => array('$last' => '$email'), 'first_name' => array('$last' => '$first_name'), 'last_name' => array('$last' => '$last_name'), 'created_at' => array('$last' => '$created_at'))), array('$limit' => '5000'), array('$project' => array('_id' => '1', 'first_name' => '1', 'last_name' => '1', 'email' => '1', 'created_at' => '1'))), array('typeMap' => array('root' => 'array', 'document' => 'array')))) in Builder.php line 307
at Collection->aggregate(array(array('$match' => array('$and' => array(array('created_at' => array('$gte' => object(UTCDateTime))), array('created_at' => array('$lt' => object(UTCDateTime)))))), array('$group' => array('_id' => array('$last' => '$_id'), 'email' => array('$last' => '$email'), 'first_name' => array('$last' => '$first_name'), 'last_name' => array('$last' => '$last_name'), 'created_at' => array('$last' => '$created_at'))), array('$limit' => '5000'), array('$project' => array('_id' => '1', 'first_name' => '1', 'last_name' => '1', 'email' => '1', 'created_at' => '1'))), array('typeMap' => array('root' => 'array', 'document' => 'array'))) in Builder.php line 307

[alok932]

This error occurs because you have selected _id field.
Change it to this.

$query->select('first_name','last_name', 'email', 'created_at')
		->groupby('email')
		->where('created_at', '>=', $startDate)
		->where('created_at', '<', $endDate);

[rlxsensors]

What happens when we need the _id after we group the data. I have the same problem but I need the _id field on the result.