How textScore field is calculated in mongodb full text search? [duplicate]
- Start with
exp = 0; - Each time the term occurs:
if exp = 0, set exp = 1, else set exp = 2 * exp; - Increment the frequency by
1/exp.
So, in fact, you are right that there is a sum of a geometric series here. If a term occurs k times, then the freq of the term (which is more like a score than a frequency, but it's called freq in the struct) will be1 + 1/2 + ... + (1/2)^(k - 1) = (1 - (1/2)^k)/(1 - 1/2) = 2 * (1 - 1/2^k)