Re: "fix" for plpgsql polymorphism

I'm going to resend the patches that I have outstanding since it appears
some may have been lost. Here's the first.
==========================================

Tom Lane wrote:
>>You can alias $0, similar to the argument variables. And, I confirmed
>>that you cannot change the value, similar to the argument variables:
>
> Perhaps you shouldn't mark it isconst; then it would actually have some
> usefulness (you could use it directly as a temporary variable to hold
> the intended result).  I can't see much value in aliasing it if it's
> const, either.

OK; the only change in this version is "isconst = false;". Now you can
use $0 as a result placeholder if desired. E.g.:

create or replace function tmp(anyelement, anyelement) returns anyarray as '
declare
   v_ret alias for $0;
   v_el1 alias for $1;
   v_el2 alias for $2;
begin
   v_ret := ARRAY[v_el1, v_el2];
   return v_ret;
end;
' language 'plpgsql';

create table f(f1 text, f2 text, f3 int, f4 int);
insert into f values ('a','b',1,2);
insert into f values ('z','x',3,4);

select tmp(f1,f2) from f;
select tmp(f3,f4) from f;

Joe

Index: src/pl/plpgsql/src/pl_comp.c
===================================================================
RCS file: /opt/src/cvs/pgsql-server/src/pl/plpgsql/src/pl_comp.c,v
retrieving revision 1.59
diff -c -r1.59 pl_comp.c
*** src/pl/plpgsql/src/pl_comp.c    1 Jul 2003 21:47:09 -0000    1.59
--- src/pl/plpgsql/src/pl_comp.c    3 Jul 2003 17:59:48 -0000
***************
*** 354,359 ****
--- 354,395 ----
                  function->fn_rettyplen = typeStruct->typlen;
                  function->fn_rettypelem = typeStruct->typelem;
                  perm_fmgr_info(typeStruct->typinput, &(function->fn_retinput));
+
+                 /*
+                  * install $0 reference, but only for polymorphic
+                  * return types
+                  */
+                 if (procStruct->prorettype == ANYARRAYOID ||
+                     procStruct->prorettype == ANYELEMENTOID)
+                 {
+                     char        buf[32];
+
+                     /* name for variable */
+                     snprintf(buf, sizeof(buf), "$%d", 0);
+
+                     /*
+                      * Normal return values get a var node
+                      */
+                     var = malloc(sizeof(PLpgSQL_var));
+                     memset(var, 0, sizeof(PLpgSQL_var));
+
+                     var->dtype = PLPGSQL_DTYPE_VAR;
+                     var->refname = strdup(buf);
+                     var->lineno = 0;
+                     var->datatype = build_datatype(typeTup, -1);
+                     var->isconst = false;
+                     var->notnull = false;
+                     var->default_val = NULL;
+
+                     /* preset to NULL */
+                     var->value = 0;
+                     var->isnull = true;
+                     var->freeval = false;
+
+                     plpgsql_adddatum((PLpgSQL_datum *) var);
+                     plpgsql_ns_additem(PLPGSQL_NSTYPE_VAR, var->varno,
+                                        var->refname);
+                 }
              }
              ReleaseSysCache(typeTup);