I ran a query using nested lists:foreach on the list of size 15000, each having lists of size about 37. This query consumed more than 5 Gb of memory, but when query was ran using tail recursion memory usage was under 1 Gb. Can anyone explain how and why is there so much difference as internally lists:foreach is also implemented using tail recursion.

 ForEach =fun
Foreach(F, [Hd|Tail]) ->
    F(Hd),
    Foreach(F, Tail);
Foreach(F, []) when is_function(F, 1) -> ok
end.

RackFunc = fun(RackId) ->
        [RackRef] = mnesia:dirty_read(rackref, RackId),
        SlotDetails = RackRef#rackref.slot_details,
        ForEach(SlotFunc, SlotDetails)
    end.
SlotFunc = fun({SlotId, SlotProperties}) ->
                        feature
                    end.

ForEach(RackFunc,RACKIDLIST)


%%Function using library:

G = fun(RackIds)->
    lists:foreach(
        fun(RackId) ->
            [RackRef] = mnesia:dirty_read(rackref, RackId),
            SlotDetails = RackRef#rackref.slot_details,
            lists:foreach(
                fun({SlotId, SlotProperties}) ->
                    feature
                    end
                end, SlotDetails)
        end, RackIds)
    end.