是否可以使用QueryBuilder管理返回数组的结构？

I'm trying to optimize my app. I need to know if what I wan to do is possible or not.

I made some try based on indexBy whitout success.

Currentely I am able to change the structure of the results array like I need via PHP.

I wan to know if QueryBuilder is able to make that for me and how (if possible).

Here is the query building :

return $this->createQueryBuilder('a')
                        ->select('SUBSTRING(a.creationDate, 1,4) year, TRIM(LEADING \'0\' FROM SUBSTRING(a.creationDate, 6,2)) month, COUNT(a) number')
                        ->where('a.creationDate > :limitDate')
                        ->groupBy('year')
                        ->addGroupBy('month')
                        ->orderBy('year', 'ASC')
                        ->addOrderBy('month', 'ASC')
                        ->setParameter('limitDate', new \DateTime("2000-01-01 00:00:00") )
                        ->getQuery()
                        ->getArrayResult();

Here is the actual result of the query :

Array (
    [0] => Array ( [year] => 2016 [month] => 10 [number] => 96 ) 
    [1] => Array ( [year] => 2016 [month] => 11 [number] => 159 ) 
    [2] => Array ( [year] => 2016 [month] => 12 [number] => 118 ) 
    [3] => Array ( [year] => 2016 [month] => 9 [number] => 47 ) 
    [4] => Array ( [year] => 2017 [month] => 1 [number] => 44 ) 
    [5] => Array ( [year] => 2017 [month] => 10 [number] => 47 )
    ...
)

Here is PHP code I use to change the array like I wan :

$myRestructuredArray = [];
foreach($myArray as $line)
{
    $myRestructuredArray [$line['year']][$line['month']] = $line['number'];
}

Here is the result I need :

Array (
    [2016] => Array ( 
        [10] => 96 
        [11] => 159 
        [12] => 118 
        [9] => 47 ) 
    [2017] => Array ( 
        [1] => 44 
        [10] => 47 
    ...
)