Refactor :only column filtering to private method
Refactor :only column filtering to private method

I prefer not to do any unnecessary calculations in #initialize, so that
objects are easier to instantiate for unit testing.
undergroundwebdesigns/pg_search,Casecommons/pg_search,paultyng/pg_search,savef/pg_search,paultyng/pg_search,zvikamenahemi/pg_search,savef/pg_search,mpivaa/pg_search,mpivaa/pg_search,rigoleto/pg_search,rigoleto/pg_search,undergroundwebdesigns/pg_search,Casecommons/pg_search,zvikamenahemi/pg_search