so far

used in negative statement to describe a situation that has existed up to this point or up to the present time; "So far he hasn't called"; "the sun isn't up yet"

to the degree or extent that; "insofar as it can be ascertained, the horse lung is comparable to that of man"; "so far as it is reasonably practical he should practice restraint"

used after a superlative; "this is the best so far"; "the largest drug bust yet"