오라클 BULK - DB CAFE

Dynamic SQL and Bulk Operations

Oracle Tips by Burleson Consulting

The following Tip is from the outstanding book "Oracle PL/SQL Tuning: Expert Secrets for High Performance Programming" by Dr. Tim Hall, Oracle ACE of the year, 2006:

The majority of the operations discussed in the previous sections are also available via dynamic SQL when using the following supported statements:

EXECUTE IMMEDIATE – This command can include a BULK COLLECT INTO or a RETURNING BULK COLLECT INTO clause.

FETCH – This command can include a BULK COLLECT INTO clause.

FORALL – The EXECUTE IMMEDIATE statement can be called as part of a FORALL statement with subscripted collection elements passed with the USING clause.

The collections specified in the USING and RETURNING clauses must represent individual column types, while collections of records are supported for BULK COLLECT INTO clauses of queries.

The dynamic_forall.sql script provides an example of using a FORALL statement to perform a bulk EXECUTE IMMEDIATE statement.

dynamic_forall.sql

DECLARE
  TYPE t_object_id_tab IS TABLE OF bulk_collect_test.object_id%TYPE;

  l_tab   t_object_id_tab;
BEGIN
  -- Populate collection use in forall.
  SELECT object_id
  BULK COLLECT INTO l_tab
  FROM   bulk_collect_test
  WHERE  rownum < 101; 

  FORALL i IN l_tab.first .. l_tab.last
    EXECUTE IMMEDIATE
      'UPDATE bulk_collect_test
       SET    object_id = object_id
       WHERE  object_id = :1'
       USING l_tab(i);
END;
/

The dynamic_forall.sql script defines a collection, populates it with some data from the test table and performs a bulk dynamic update.

Both the EXECUTE IMMEDIATE and the FETCH statements can be used populate collections from dynamic queries using the BULK COLLECT clause, as shown in the dynamic_bulk_collect.sql script listed below.

dynamic_bulk_collect.sql

SET SERVEROUTPUT ON
DECLARE
  TYPE t_bulk_collect_test_tab IS TABLE OF bulk_collect_test%ROWTYPE;

  l_tab     t_bulk_collect_test_tab;
  l_cursor  SYS_REFCURSOR;
BEGIN
  OPEN l_cursor FOR 'SELECT * FROM bulk_collect_test';
  FETCH l_cursor
  BULK COLLECT INTO l_tab;
  CLOSE l_cursor; 

  DBMS_OUTPUT.put_line('Dynamic FETCH  : ' || l_tab.count);

  EXECUTE IMMEDIATE 'SELECT * FROM bulk_collect_test'
  BULK COLLECT INTO l_tab;

  DBMS_OUTPUT.put_line('Dynamic EXECUTE: ' || l_tab.count);
END;
/

The results of the dynamic_bulk_collect.sql script show that both the FETCH and the EXECUTE IMMEDIATE methods return the same results.

SQL> @dynamic_bulk_collect.sql
Dynamic FETCH  : 61204
Dynamic EXECUTE: 61204

PL/SQL procedure successfully completed.

The dynamic_returning_bulk_collect.sql script shows how the RETURNING clause can be used in a dynamic bulk operation.

dynamic_returning_bulk_collect.sql

SET SERVEROUTPUT ON
DECLARE
  TYPE t_object_id_tab IS TABLE OF bulk_collect_test.object_id%TYPE;

  l_tab  t_object_id_tab;
BEGIN
  EXECUTE IMMEDIATE
    'DELETE FROM bulk_collect_test
     RETURNING object_id  INTO :1'
     RETURNING BULK COLLECT INTO l_tab;

  DBMS_OUTPUT.put_line('Deleted IDs : ' || l_tab.count || ' rows');

  ROLLBACK;
END;
/

As expected the collection is populated with the IDs of the deleted rows.

SQL> @dynamic_returning_bulk_collect.sql
Deleted IDs : 61204 rows

PL/SQL procedure successfully completed.

SQL>

Finally, the dynamic_forall_returning_bulk_collect.sql script combines most of these options into a single script to show their interaction.

dynamic_forall_returning_bulk_collect.sql

SET SERVEROUTPUT ON
DECLARE
  TYPE t_object_id_tab IS TABLE OF bulk_collect_test.object_id%TYPE;

  l_in_tab   t_object_id_tab;
  l_out_tab  t_object_id_tab;
BEGIN
  -- Populate collection use in forall.
  EXECUTE IMMEDIATE
    'SELECT object_id
     FROM   bulk_collect_test
     WHERE   rownum < 101'
  BULK COLLECT INTO l_in_tab;

  FORALL i IN l_in_tab.first .. l_in_tab.last
    EXECUTE IMMEDIATE
      'DELETE FROM bulk_collect_test
       WHERE  object_id = :1
       RETURNING object_id INTO :2'
       USING l_in_tab(i) RETURNING BULK COLLECT INTO l_out_tab;

  DBMS_OUTPUT.put_line('Starting IDs : ' || l_in_tab.count || ' rows');
  DBMS_OUTPUT.put_line('Deleted IDs  : ' || l_out_tab.count || ' rows');

  ROLLBACK;END;
/

The results of the dynamic_forall_returning_bulk_collect.sql script show that the input collection is bound into the statement correctly and that the IDs of the deleted rows are returned as expected.

SQL>  @dynamic_forall_returning_bulk_collect.sql

Starting IDs : 100 rows Deleted IDs : 100 rows

PL/SQL procedure successfully completed.

These examples should give you a feel for what is possible when combining dynamic SQL and bulk operations.