>>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 Conway

diff --git a/src/pl/plpgsql/src/pl_comp.c b/src/pl/plpgsql/src/pl_comp.c
index 1a84cdfd667bcd3a00367a3f8cf4246e32c76e6b..d1ed57a6773b37d213790a8577e85c76c692feed 100644 (file)
--- a/src/pl/plpgsql/src/pl_comp.c
+++ b/src/pl/plpgsql/src/pl_comp.c
@@ -3,7 +3,7 @@
  *           procedural language
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.60 2003/07/25 23:37:28 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.61 2003/07/26 23:58:23 momjian Exp $
  *
  *   This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -361,6 +361,42 @@ do_compile(FunctionCallInfo fcinfo,
                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);