Make plpgsql provide the typmods for its variables to the main parser.

Historically we didn't do this, even though we had the information, because
plpgsql passed its Params via SPI APIs that only include type OIDs not
typmods.  Now that plpgsql uses parser callbacks to create Params, it's
easy to insert the right typmod.  This should generally result in lower
surprise factors, because a plpgsql variable that is declared with a typmod
will now work more like a table column with the same typmod.  In particular
it's the "right" way to fix bug #6020, in which plpgsql's attempt to return
an anonymous record type is defeated by stricter record-type matching
checks that were added in 9.0.  However, it's not impossible that this
could result in subtle behavioral changes that could break somebody's
existing plpgsql code, so I'm afraid to back-patch this change into
released branches.  In those branches we'll have to lobotomize the
record-type checks instead.

src/pl/plpgsql/src/pl_comp.c

@@ -1267,9 +1267,11 @@ make_datum_param(PLpgSQL_expr *expr, int dno, int location)
 	param = makeNode(Param);
 	param->paramkind = PARAM_EXTERN;
 	param->paramid = dno + 1;
-	param->paramtype = exec_get_datum_type(estate, datum);
-	param->paramtypmod = -1;
-	param->paramcollid = exec_get_datum_collation(estate, datum);
+	exec_get_datum_type_info(estate,
+							 datum,
+							 &param->paramtype,
+							 &param->paramtypmod,
+							 &param->paramcollid);
 	param->location = location;
 
 	return (Node *) param;

src/pl/plpgsql/src/pl_exec.c

@@ -4307,29 +4307,63 @@ exec_get_datum_type(PLpgSQL_execstate *estate,
 }
 
 /*
- * exec_get_datum_collation				Get collation of a PLpgSQL_datum
+ * exec_get_datum_type_info			Get datatype etc of a PLpgSQL_datum
+ *
+ * An extended version of exec_get_datum_type, which also retrieves the
+ * typmod and collation of the datum.
  */
-Oid
-exec_get_datum_collation(PLpgSQL_execstate *estate,
-						 PLpgSQL_datum *datum)
+void
+exec_get_datum_type_info(PLpgSQL_execstate *estate,
+						 PLpgSQL_datum *datum,
+						 Oid *typeid, int32 *typmod, Oid *collation)
 {
-	Oid			collid;
-
 	switch (datum->dtype)
 	{
 		case PLPGSQL_DTYPE_VAR:
 			{
 				PLpgSQL_var *var = (PLpgSQL_var *) datum;
 
-				collid = var->datatype->collation;
+				*typeid = var->datatype->typoid;
+				*typmod = var->datatype->atttypmod;
+				*collation = var->datatype->collation;
 				break;
 			}
 
 		case PLPGSQL_DTYPE_ROW:
+			{
+				PLpgSQL_row *row = (PLpgSQL_row *) datum;
+
+				if (!row->rowtupdesc)	/* should not happen */
+					elog(ERROR, "row variable has no tupdesc");
+				/* Make sure we have a valid type/typmod setting */
+				BlessTupleDesc(row->rowtupdesc);
+				*typeid = row->rowtupdesc->tdtypeid;
+				/* do NOT return the mutable typmod of a RECORD variable */
+				*typmod = -1;
+				/* composite types are never collatable */
+				*collation = InvalidOid;
+				break;
+			}
+
 		case PLPGSQL_DTYPE_REC:
-			/* composite types are never collatable */
-			collid = InvalidOid;
-			break;
+			{
+				PLpgSQL_rec *rec = (PLpgSQL_rec *) datum;
+
+				if (rec->tupdesc == NULL)
+					ereport(ERROR,
+						  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+						   errmsg("record \"%s\" is not assigned yet",
+								  rec->refname),
+						   errdetail("The tuple structure of a not-yet-assigned record is indeterminate.")));
+				/* Make sure we have a valid type/typmod setting */
+				BlessTupleDesc(rec->tupdesc);
+				*typeid = rec->tupdesc->tdtypeid;
+				/* do NOT return the mutable typmod of a RECORD variable */
+				*typmod = -1;
+				/* composite types are never collatable */
+				*collation = InvalidOid;
+				break;
+			}
 
 		case PLPGSQL_DTYPE_RECFIELD:
 			{
@@ -4350,21 +4384,27 @@ exec_get_datum_collation(PLpgSQL_execstate *estate,
 							(errcode(ERRCODE_UNDEFINED_COLUMN),
 							 errmsg("record \"%s\" has no field \"%s\"",
 									rec->refname, recfield->fieldname)));
-				/* XXX there's no SPI_getcollid, as yet */
+				*typeid = SPI_gettypeid(rec->tupdesc, fno);
+				/* XXX there's no SPI_gettypmod, for some reason */
+				if (fno > 0)
+					*typmod = rec->tupdesc->attrs[fno - 1]->atttypmod;
+				else
+					*typmod = -1;
+				/* XXX there's no SPI_getcollation either */
 				if (fno > 0)
-					collid = rec->tupdesc->attrs[fno - 1]->attcollation;
+					*collation = rec->tupdesc->attrs[fno - 1]->attcollation;
 				else	/* no system column types have collation */
-					collid = InvalidOid;
+					*collation = InvalidOid;
 				break;
 			}
 
 		default:
 			elog(ERROR, "unrecognized dtype: %d", datum->dtype);
-			collid = InvalidOid;	/* keep compiler quiet */
+			*typeid = InvalidOid;	/* keep compiler quiet */
+			*typmod = -1;
+			*collation = InvalidOid;
 			break;
 	}
-
-	return collid;
 }
 
 /* ----------

src/pl/plpgsql/src/plpgsql.h

@@ -905,8 +905,9 @@ extern void plpgsql_subxact_cb(SubXactEvent event, SubTransactionId mySubid,
 				   SubTransactionId parentSubid, void *arg);
 extern Oid exec_get_datum_type(PLpgSQL_execstate *estate,
 					PLpgSQL_datum *datum);
-extern Oid exec_get_datum_collation(PLpgSQL_execstate *estate,
-						 PLpgSQL_datum *datum);
+extern void exec_get_datum_type_info(PLpgSQL_execstate *estate,
+						 PLpgSQL_datum *datum,
+						 Oid *typeid, int32 *typmod, Oid *collation);
 
 /* ----------
  * Functions for namespace handling in pl_funcs.c