references(*table_names)
Instance Public methods
Use to indicate that the given table_names are referenced by
an SQL string, and should therefore be JOINed in any query rather than
loaded separately. This method only works in conjuction with
includes. See includes for more details.
User.includes(:posts).where("posts.name = 'foo'")
# => Doesn't JOIN the posts table, resulting in an error.
User.includes(:posts).where("posts.name = 'foo'").references(:posts)
# => Query now know