class ActiveRecord::ConnectionAdapters::PostgreSQL::SchemaCreation

def visit_UniqueConstraintDefinition(o)
  column_name = Array(o.column).map { |column| quote_column_name(column) }.join(", ")
  sql = ["CONSTRAINT"]
  sql << quote_column_name(o.name)
  sql << "UNIQUE"
  sql << "NULLS NOT DISTINCT" if supports_nulls_not_distinct? && o.nulls_not_distinct
  if o.using_index
    sql << "USING INDEX #{quote_column_name(o.using_index)}"
  else
    sql << "(#{column_name})"
  end
  if o.deferrable
    sql << "DEFERRABLE INITIALLY #{o.deferrable.to_s.upcase}"
  end
  sql.join(" ")
end