For example, here is distribution of q-grams count in 120 Mb of dblp paper titles (pretty large dataset). q count 2 7218 3 115107 4 589428 5 1648453 6 3336685 Number of 5-grams if about 15x larger than number of 3-grams. But most part of index space will be occupied by links to the rows(about 120 millions of links), while size of q-grams itself will be almost ignorable in comparison with it.
---- With best regards, Alexander Korotkov.
