How to append a sparse domain in Chapel

I'm populating a sparse array in Chapel with a loop that is reading over a CSV.

I'm wondering what the best pattern is.

var dnsDom = {1..n_dims, 1..n_dims};
var spsDom: sparse subdomain(dnsDom);
for line in file_reader.lines() {
   var i = line[1]:int;
   var j = line[2]:int;
   spsDom += (i,j);
}

Is this an efficient way of doing it?
Should I create a temporary array of tuples and append spsDom every ( say ) 10,000 rows?

Thanks!