delim corresponds to the `typdelim` column in the pg_types table. subtype is derived from the `typelem` column in the pg_types table.

# File activerecord/lib/active_record/connection_adapters/postgresql/oid.rb, line 68
def initialize(delim, subtype)
  @delim   = delim
  @subtype = subtype
end

FIXME: this should probably split on delim and use subtype to cast the values. Unfortunately, the current Rails behavior is to just return the string.

# File activerecord/lib/active_record/connection_adapters/postgresql/oid.rb, line 76
def type_cast(value)
  value
end