For a query word, to generate all candidates after applying the four operations, we can calculate the number of words we need to generate and test its correctness. For a word of length n, an alphabet size a, an edit distance d=1, there will be n deletions, n-1 transpositions, a*n alterations, and a*(n+1) insertions, for a total of 2n+2an+a-1 terms at search time. In the case of Malayalam, a is 117 if we consider all encoded characters in Unicode version 11. If we remove all archaic characters, we still need about 75 characters. So, for edit distance d=1, a=75, for a word with 10 characters, 2*10+2*75*10+75-1 = 1594 and much larger for larger d. So, you will need to do 1594 lookups(spellchecks) in the language model to get possible suggestions.