Initial state on the server. The only UDF method called during the Initial state is _start_extfn.
The server calls the start method for each instance of the UDF created. If a query is executed by a single server thread, then the start method is called once. If a query is handled by several threads, or distributed across several nodes, the server creates different UDF instances and, as a result, the start method is called several times.
UDFs can set function instance level data within the _user_data field of the a_v4_extfn_proc_context structure, which is the argument to the start method.