Passing Tables back from Java Stored Procedures

Question

Thomas Kyte has written (in reference to
trying to pass an array back from a stored
function call):
You can do one of two things (and both require the use of
objects). You cannot use PLSQL table types as JDBC cannot bind to
this type -- we must use OBJECT Types.
[snip]
Another way is to use a result set and "select * from
plsql_function". It could look like this:
ops$tkyte@8i> create or replace type myTableType as table of
varchar2 (64);
2 /
Type created.
ops$tkyte@8i>
ops$tkyte@8i>
ops$tkyte@8i> create or replace
2 function demo_proc2( p_rows_to_make_up in number )
3 return myTableType
4 as
5 l_data myTableType := myTableType();
6 begin
7 for i in 1 .. p_rows_to_make_up
8 loop
9 l_data.extend;
10 l_data(i) := 'Made up row ' | | i;
11 end loop;
12 return l_data;
13 end;
14 /
Function created.
ops$tkyte@8i>
ops$tkyte@8i> select *
2 from the ( select cast( demo_proc2(5) as mytableType )
3 from dual );
COLUMN_VALUE
Made up row 1
Made up row 2
Made up row 3
Made up row 4 [Image]
Made up row 5
So, your JDBC program would just run the query to get the data.
If the function "demo_proc2" cannot be called from SQL for
whatever reason (eg: it calls an impure function in another piece
of code or it itself tries to modify the database via an insert
or whatever), you'll just make a package like:
ops$tkyte@8i> create or replace package my_pkg
2 as
3
4 procedure Make_up_the_data( p_rows_to_make_up in
number ); 5 function Get_The_Data return myTableType;
6 end;
7 /
Package created.
ops$tkyte@8i>
ops$tkyte@8i> create or replace package body my_pkg
2 as
3
4 g_data myTableType;
5
6 procedure Make_up_the_data( p_rows_to_make_up in number )
7 as
8 begin
9 g_data := myTableType();
10 for i in 1 .. p_rows_to_make_up
11 loop
12 g_data.extend;
13 g_data(i) := 'Made up row ' | | i;
14 end loop;
15 end;
16
17
18 function get_the_data return myTableType
19 is
20 begin
21 return g_data;
22 end;
23
24 end;
25 /
Package body created.
ops$tkyte@8i>
ops$tkyte@8i> exec my_pkg.make_up_the_data( 3 );
PL/SQL procedure successfully completed.
ops$tkyte@8i>
ops$tkyte@8i> select *
2 from the ( select cast( my_pkg.get_the_data as mytableType
) 3 from dual );
COLUMN_VALUE
Made up row 1
Made up row 2
Made up row 3
And you'll call the procedure followed by a query to get the
data...
I have tried this, and it works perfectly.
My question, is what does the wrapper look
like if the stored function is written
in java instead of PL/SQL? My experiments
with putting the function in java have been
dismal failures. (I supposed I should also
ask how the java stored procedure might
look also, as I suppose that could be where
I have been having a problem)
null

Answer 1

Thanks for the response Avi, but I think I need to clarify my question. The articles referenced in your link tended to describe using PL/SQL ref cursors in Java stored procedures and also the desire to pass ref cursors from Java to PL/SQL programs. Unfortunately, what I am looking to do is the opposite.
We currently have several Java stored procedures that are accessed via select statements that have become a performance bottleneck in our system. Originally the business requirements were such that only a small number of rows were ever selected and passed into the Java stored procedures. Well, business requirements have changed and now thousands and potentially tens of thousands of rows can be passed in. We benchmarked Java stored procedures vs. PL/SQL stored procedures being accessed via a select statement and PL/SQL had far better performance and scaleable. So, our thought is by decouple the persistence logic into PL/SQL and keeping the business logic in Java stored procedures we can increase performance without having to do a major rewrite of the existing code. This leads to the current problem.
What we currently do is select into a Java stored procedure which has many database access calls. What we would like to do is select against a PL/SQL stored procedure to aggregate the data and then pass that data via a ref cursor (or whatever structure is acceptable) to a Java stored procedure. This would save us a significant amount of work since the current Java stored procedures would simple need to be changed to not make database calls since the data would be handed to them.
Is there a way to send a ref cursor from PL/SQL as an input parameter to a Java stored procedure? My call would potentially look like this:
SELECT java_stored_proc(pl/sql_stored_proc(col_id))
FROM table_of_5000_rows;
Sorry for the lengthy post.