Issue in using Cursor+Dynamic SQL+ Bulk collect +FORALL

Question

Hi,
I have a dynamic query which I need to use as a cursor to fetch records that inturn need to be inserted into a staging table.
The issue I am facing is I am not sure how to declare the variable to fetch the records into. Since I am using a dynamic cursor how do I declare it?
My code looks something like this -
TYPE c_details_tbl_type IS REF CURSOR;
c_details c_details_tbl_type;
TYPE c_det_tbl_type IS TABLE OF c_details%ROWTYPE INDEX BY PLS_INTEGER;
c_det_tbl c_det_tbl_type; -- ???
BEGIN
v_string1 := 'SELECT....'
v_string2 := ' UNION ALL SELECT....'
v_string3 := 'AND ....'
v_string := v_string1||v_string2||v_string3;
OPEN c_details FOR v_string;
LOOP
FETCH c_details BULK COLLECT
INTO c_det_tbl LIMIT 1000;
IF (c_det_tbl.COUNT > 0) THEN
          DELETE FROM STG;
          FORALL i IN 1..c_det_tbl.COUNT
          INSERT INTO STG
          VALUES (c_det_tbl(i));
END IF;
EXIT WHEN c_details%NOTFOUND;
END LOOP;
CLOSE c_details;
END
Thanks

Answer 1

Why the bulk collect? All that this does is slow down the read process (SELECT) and write process (INSERT).
Data selected needs (as a collection) to be pushed into the PGA memory of the PL/SQL engine. And then that very same data needs to be pushed again by the PL/SQL engine back to the database to be inserted. Why?
It is a lot faster, needs a lot less resources, with fewer moving parts, to simply instruct the SQL engine to do both these steps using a single INSERT..SELECT statement. And this can support parallel DML too for scalability when data volumes get large.
It is also pretty easy to make a single SQL statement like this dynamic and even support bind variables.
Simplicity is the ultimate form of elegance. Pushing data needlessly around is not simple and thus not a very elegant way to address the problem.