How to “optimally” calculate the number of elements by property in Bitrix?

Question

1C-Bitrix

Good afternoon.
There is "Infoblock 2.0", with property "source" type list (list in $arSource), about 100k+ elements.
It is necessary to count the number of elements for each property from the list.

$arSource = ["google","yandex","mail","avito", "еще 10 элементов"]; 
    foreach ($arSource as $s)
        $uCnt[$s] = \Bitrix\Iblock\Elements\ElementApivatsmtsTable::getList(['filter' => ['source.VALUE'=>$s], 'count_total' => 1])->getCount();

An example of what I sketched - it works, but the sampling takes much longer than we would like (about 2 seconds).
Taking into account the fact that the number of elements will increase, I would like it to be faster. Can you suggest a more optimal sample for my case?

Answer 1

Make a query with grouping and counting. Example:

\Bitrix\Iblock\Elements\ElementCatalogTable::getList([
    "select" => [
        "BRAND_VALUE" => "BRAND.VALUE",
        "COUNT",
    ],
    "filter" => [
        "!BRAND.VALUE" => false
    ],
    "group" => [
        "BRAND.VALUE"
    ],
    "runtime" => [
        new \Bitrix\Main\ORM\Fields\ExpressionField('COUNT',  'COUNT(*)' )
    ]
])

Answer 2

I would first do a getList and work with the result.
I heard that database queries in a cycle are not very good =)