anchor.diff:  
   %% @doc find type by OID
   -spec find_by_oid(oid(), db()) -> type_info() | undefined.
  -%% find_by_oid(?RECORD_OID, _) ->
  -%%     '$record';
   find_by_oid(Oid, #oid_db{by_oid = Dict}) ->
       kv_get(Oid, Dict, undefined).
   
  
positive.code:     Types = join(",",
                   [["'", ToBin(TypeName) | "'"]
                    || TypeName <- TypeNames]),
      [<<"SELECT typname, oid::int4, typarray::int4 "
         "FROM pg_type "
         "WHERE typname IN (">>, Types, <<") ORDER BY typname">>].
  
  
negative.code:          codec_state :: any()}).
  -record(oid_db,
          {by_oid :: kv(oid(), #type{}),
           by_name :: kv(epgsql:type_name(), oid())}).
  
  -type oid() :: non_neg_integer().
  %% Row of `typname', `oid', `typarray' from pg_type table.
  -type oid_entry() :: {epgsql:type_name(), Oid :: oid(), ArrayOid :: oid()}.
  -type oid_info() :: {Oid :: oid(), epgsql:type_name(), IsArray :: boolean()}.
  -opaque db() :: #oid_db{}.
  -opaque type_info() :: #type{}.
  
  
  %%
  