Available sets are

A={"one","two","three"}
B={"two","three","four"}
c={"four","five"}

Given set is

D = {"four","five","six"}

The task is to find which available set has most intersecting elements to given set.

Here

C contains 2 fields of D

B contains 1 field of D.

This can be computed by finding the union of D with A, B, C.

How to find which available set has most intersecting elements to given set when
dataset contains a million items and million unique fields.