Implementing client transforms for binding in from a client using external UDFs

The following DDL registers a function that takes the VARCHAR-encoded object from the client, decomposes it into its various base type attributes, and passes it to the TO SQL function transform.

   CREATE FUNCTION to_sql_from_client (VARCHAR (150))
      RETURNS Address_t
      LANGUAGE C
      TRANSFORM GROUP func_group
      EXTERNAL NAME 'addressudf!address_to_sql_from_client'
      DETERMINISTIC
      NO EXTERNAL ACTION
      NOT FENCED
      NO SQL
      PARAMETER STYLE SQL;

Although it appears as if the to_sql_from_client returns the address directly, what really happens is that to_sql_from_client converts the VARCHAR (150) to a set of base type attributes. Then implicitly invokes the TO SQL transform functoaddress to construct the address object that is returned to the database.

Notice that the DDL in to_sql_from_client includes a clause called TRANSFORM GROUP. This clause tells which set of transforms to use in processing the address type in those functions.