An example of how to add a custom predicate to Arel

arel_any_predicate.rb

module Arel::Predications
  def any(right)
    Arel::Nodes::Any.new(self, quoted_node(right))
  end
end

class Arel::Nodes::Any < Arel::Nodes::Binary
  def operator
    :'ANY'
  end
end

class Arel::Visitors::PostgreSQL

  private

  def visit_Arel_Nodes_Any(o, collector)
    collector = visit o.right, collector
    collector << " = #{Arel::Nodes::Any.new(nil, nil).operator} ("
    visit(o.left, collector) << ")"
  end
end

puts User.where(User.arel_table[:roles].any('superadmin')).to_sql
SELECT "users".* FROM "users" WHERE ('superadmin' = ANY ("users"."roles"))