php - How to clear magento 2 object instance? -

i have product collection using below code.

$productcollection = $url->create('magento\catalog\model\resourcemodel\product\collectionfactory');

$collection = $productcollection->create()->addattributetoselect('*')->load();

using above code have tried insert attribute value.

using below code have insert attribute code.

$product_coll->load($_product->getid())->setdata('view_page_product', $more_set_ids)->save();

but faced 1 issue.

automatically product blank attribute value use above product data.

ex. product id : 4,5

4 product attribute: dimension: 15w * 14h

5 product attribute: dimension: "blank"

i have run script 4 product dimension automatically insert in product 5.

so please tell me solution. how fix issue.

thanks :)