https://en.wikipedia.org/wiki/Okapi_BM25
create or replace view doc_len
as
select
docid, count(1) as cnt
from
exploded
group by
docid
;
select avg(cnt) as avgdl from doc_len;
tf(q_i,D)
, |D|
, avgdl
, N
, n(q_i)
Hyperparameters: k_1
, b