How to use session-global variables of type collection in oracle - oracle

Question

I have a package which declares a collection of type table of some database table's %rowtype. It also declares a function to populate the package-level variable with some data. I can now print the data with dbms_output, seems fine.
But when I use the package-level variable in some sql I get the following error:
ORA-21700: object does not exist or is marked for delete
ORA-06512: at "TESTDB.SESSIONGLOBALS", line 17
ORA-06512: at line 5
Here is my code:
create some dummy data:
drop table "TESTDATA";
/
CREATE TABLE "TESTDATA"
( "ID" NUMBER NOT NULL ENABLE,
"NAME" VARCHAR2(20 BYTE),
"STATUS" VARCHAR2(20 BYTE)
);
/
insert into "TESTDATA" (id, name, status) values (1, 'Hans Wurst', 'J');
insert into "TESTDATA" (id, name, status) values (2, 'Hans-Werner', 'N');
insert into "TESTDATA" (id, name, status) values (3, 'Hildegard v. Bingen', 'J');
/
now create the package:
CREATE OR REPLACE
PACKAGE SESSIONGLOBALS AS
type t_testdata is table of testdata%rowtype;
v_data t_testdata := t_testdata();
function load_testdata return t_testdata;
END SESSIONGLOBALS;
and the package body:
CREATE OR REPLACE
PACKAGE BODY SESSIONGLOBALS AS
function load_testdata return t_testdata AS
v_sql varchar2(500);
BEGIN
if SESSIONGLOBALS.v_data.count = 0
then
v_sql := 'select * from testdata';
execute immediate v_sql
bulk collect into SESSIONGLOBALS.v_data;
dbms_output.put_line('data count:');
dbms_output.put_line(SESSIONGLOBALS.v_data.count);
end if; -- SESSIONGLOBALS.v_data.count = 0
-- ******************************
-- this line throws the error
insert into testdata select * from table(SESSIONGLOBALS.v_data);
-- ******************************
return SESSIONGLOBALS.v_data;
END load_testdata;
END SESSIONGLOBALS;
execute the sample:
DECLARE
v_Return SESSIONGLOBALS.T_TESTDATA;
BEGIN
v_Return := SESSIONGLOBALS.LOAD_TESTDATA();
dbms_output.put_line('data count (direct access):');
dbms_output.put_line(SESSIONGLOBALS.v_data.count);
dbms_output.put_line('data count (return value of function):');
dbms_output.put_line(v_Return.count);
END;
If the line marked above is commented out i get the expected result.
So can anyone tell me why the exception stated above occurs?
BTW: it is absolutely nessecary for me to execute the statement which populates the collection with data as dynamic sql because the tablename is not known at compiletime. (v_sql := 'select * from testdata';)

Answer 1

the solution is to use pipelined functions in the package
see: http://docs.oracle.com/cd/B19306_01/appdev.102/b14289/dcitblfns.htm#CHDJEGHC ( => section Pipelining Between PL/SQL Table Functions does the trick).
my package looks like this now (please take the table script from my question):
create or replace
PACKAGE SESSIONGLOBALS AS
v_force_refresh boolean;
function set_force_refresh return boolean;
type t_testdata is table of testdata%rowtype;
v_data t_testdata;
function load_testdata return t_testdata;
function get_testdata return t_testdata pipelined;
END SESSIONGLOBALS;
/
create or replace
PACKAGE BODY SESSIONGLOBALS AS
function set_force_refresh return boolean as
begin
SESSIONGLOBALS.v_force_refresh := true;
return true;
end set_force_refresh;
function load_testdata return t_testdata AS
v_sql varchar2(500);
v_i number(10);
BEGIN
if SESSIONGLOBALS.v_data is null then
SESSIONGLOBALS.v_data := SESSIONGLOBALS.t_testdata();
end if;
if SESSIONGLOBALS.v_force_refresh = true then
SESSIONGLOBALS.v_data.delete;
end if;
if SESSIONGLOBALS.v_data.count = 0
then
v_sql := 'select * from testdata';
execute immediate v_sql
bulk collect into SESSIONGLOBALS.v_data;
end if; -- SESSIONGLOBALS.v_data.count = 0
return SESSIONGLOBALS.v_data;
END load_testdata;
function get_testdata return t_testdata pipelined AS
v_local_data SESSIONGLOBALS.t_testdata := SESSIONGLOBALS.load_testdata();
begin
if v_local_data.count > 0 then
for i in v_local_data.first .. v_local_data.last
loop
pipe row(v_local_data(i));
end loop;
end if;
end get_testdata;
END SESSIONGLOBALS;
/
now i can do a select in sql like this:
select * from table(SESSIONGLOBALS.get_testdata());
and my data collection is only populated once.
nevertheless it is quite not comparable with a simple
select * from testdata;
from a performace point of view but i'll try out this concept for some more complicated use cases. the goal is to avoid doing some really huge select statements involving lots of tables distributed among several schemas (english plural for schema...?).

Answer 2

The syntax you use does not work:
insert into testdata select * from table(SESSIONGLOBALS.v_data); -- does not work
You have to use something like that:
forall i in 1..v_data.count
INSERT INTO testdata VALUES (SESSIONGLOBALS.v_data(i).id,
SESSIONGLOBALS.v_data(i).name,
SESSIONGLOBALS.v_data(i).status);
(which actually duplicates the rows in the table)

Answer 3

Package-level types cannot be used in SQL. Even if your SQL is called from within a package, it still can't see that package's types.
I'm not sure how you got that error message, when I compiled the package I got this error, which gives a good hint at the problem:
PLS-00642: local collection types not allowed in SQL statements
To fix this problem, create a type and a nested table of that type:
create or replace type t_testdata_rec is object
(
"ID" NUMBER,
"NAME" VARCHAR2(20 BYTE),
"STATUS" VARCHAR2(20 BYTE)
);
create or replace type t_testdata as table of t_testdata_rec;
/
The dynamic SQL to populate the package variable gets more complicated:
execute immediate
'select cast(collect(t_testdata_rec(id, name, status)) as t_testdata)
from testdata ' into SESSIONGLOBALS.v_data;
But now the insert will work as-is.