add MAX/MIN in list views for integer values in admin

[KalimAz]

Prestashop 1.6.1.23

As far as I can see the list object has MAX/MIN if the date is DATE type. Does anyone knows where is this object build so I can add MAX/MIN also to Integer columns?

For example in AdminProductsControler I can't indicate see product with stock ( quantyty min 1 ), I have seen that this is implemented on 1.7.x, but where is that done. For sure is in the constructor of the list view ( for instance I see that if the var assigned is DATE, also in 1.6.1.23 I have a MAX/MIN date filter ).

Can anyone help me on that

Thanks in advance