Tom Lane wrote:
Joe Conway <[EMAIL PROTECTED]> writes:
The attached patch enables PL/pgSQL functions (but not triggers) to accept and return polymorphic types. It is careful to return false from func_up_to_date() if any of the polymorphic types change from call-to-call.

I don't think you can usefully do it that way. Suppose the same function is being invoked in two places in a query, with two different actual argument types at the two spots. Won't this setup result in dropping and rebuilding the function cache twice per row?

Actually, no. Every compile of the function gets added to a linked list, and a subsequent call checks the list for a compiled version matching the funcoid and argument/return types; from plpgsql_call_handler():


<snip>
if (func == NULL)
{
  /*
   * Check if we already compiled this function for another caller
   */
  for (func = compiled_functions; func != NULL; func = func->next)
  {
    if (funcOid == func->fn_oid && func_up_to_date(func, fcinfo))
    break;
  }

  /*
   * If not, do so and add it to the compiled ones
   */
  if (func == NULL)
  {
    func = plpgsql_compile(funcOid,
                           isTrigger ? T_TRIGGER : T_FUNCTION,
                           fcinfo);
    func->next = compiled_functions;
    compiled_functions = func;
  }
</snip>

You've really got to arrange for there to be a separate function cache
entry for each set of argument types --- in other words, the actual arg
types have to be part of the cache key.

See above; it already does that. Actually, that's not even new, but it did work out nice for this purpose.


(It might be time to change the  cache lookup into a hashtable instead of
a simple linear list search...)

I could do that if you want, but do you really think it's worth it? How long does a linked list have to get before a hash table starts to be a win (this is something I've always wondered about anyway)?


It also falls back to the pg_proc declared types if the caller didn't setup the FuncExpr node.

This will result in "plpgsql functions cannot return type anyarray" which is at best misleading. It'd be better to have a specific error message, say "could not determine actual return type for polymorphic function %s".

OK, that's an easy change.


Thanks,

Joe




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