ruby on rails - Calculate offset of a row -


i writing server side on ror, uses postgresql.

today faced feature, in need identify current offset of row in table. client send me unique identifier , need return current offset of item.

so, have table 'items' , model 'item'.

item has unique field. let's call 'key'.

for instance, 'items' table has data:

id |  key ---------- 0  |  abb  1  |  acc  3  |  cbb  5  |  aqq

if client send me key 'aqq'. should output 4. if client send me 'acc'. should output 2.

if there way without loading data table , going through in loop?

thanks in advance!

if wanted through activerecord like:

item.where("id <= ?", item.find_by_key("aqq").id).count

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