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Bulk UPDATE Operations
Oracle Tips by Burleson Consulting
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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 forall_test table is used to compare the
performance of individual updates against bulk updates using the
update_forall.sql script listed below. Notice the use of the ROW
keyword in the bulk operation. This keyword was introduced in
Oracle9i Release 2 to allow updates using record definitions without
needing to reference individual elements of the record, making bulk
operations significantly simpler.
update_forall.sql
SET
SERVEROUTPUT ON
DECLARE
TYPE t_id_tab IS TABLE OF forall_test.id%TYPE;
TYPE t_forall_test_tab IS TABLE OF forall_test%ROWTYPE;
l_id_tab t_id_tab
:= t_id_tab();
l_tab t_forall_test_tab := t_forall_test_tab ();
l_start NUMBER;
l_size NUMBER
:= 10000;
BEGIN
-- Populate collections.
FOR i IN 1 .. l_size LOOP
l_id_tab.extend;
l_tab.extend;
l_id_tab(l_id_tab.last) := i;
l_tab(l_tab.last).id
:= i;
l_tab(l_tab.last).code
:= TO_CHAR(i);
l_tab(l_tab.last).description := 'Description: ' || TO_CHAR(i);
END LOOP;
--
Time regular updates.
l_start := DBMS_UTILITY.get_time;
FOR i
IN l_tab.first .. l_tab.last LOOP
UPDATE forall_test
SET ROW = l_tab(i)
WHERE id = l_tab(i).id;
END LOOP;
DBMS_OUTPUT.put_line('Normal Updates : ' ||
(DBMS_UTILITY.get_time - l_start));
l_start := DBMS_UTILITY.get_time;
--
Time bulk updates.
FORALL i IN l_tab.first .. l_tab.last
UPDATE forall_test
SET ROW = l_tab(i)
WHERE id = l_id_tab(i);
DBMS_OUTPUT.put_line('Bulk Updates : ' ||
(DBMS_UTILITY.get_time - l_start));
COMMIT;
END;
/
The update_forall.sql script has a similar
internal structure to the insert_forall.sql script described earlier.
The main difference is the update statement requires a WHERE clause
that references the tables ID column allowing individual rows to be
targeted. If the bulk operation was altered to reference the ID
column within the collection, the following compilation error would be
produced.
--
Incorrect bulk operation.
FORALL i IN l_tab.first .. l_tab.last
UPDATE forall_test
SET ROW = l_tab(i)
WHERE id = l_tab(i).id;
Errors for
PROCEDURE UPDATE_FORALL:
LINE/COL
ERROR
-------- -----------------------------------------------------------
36/5 PL/SQL: SQL Statement ignored
38/18 PL/SQL: ORA-22806: not an object or REF
38/18 PLS-00382: expression is of wrong type
38/18 PLS-00436: implementation restriction: cannot
reference
fields of BULK In-BIND table of
records
Before running the script make sure the
FORALL_TEST table is populated using the insert_forall.sql script or
there will be no records to update. The results from the
update_forall.sql script are listed below.
SQL> @update_forall.sql
Normal Updates : 202
Bulk Updates : 104
PL/SQL
procedure successfully completed.
In this example, the bulk operation is
approximately twice the speed of the conventional update.
The update_forall_8i.sql script shows how this
operation would be coded prior to Oracle9i Release 2. Notice
that a separate collection is defined for each column referenced in
the bind operation.
update_forall_8i.sql
SET
SERVEROUTPUT ON
DECLARE
TYPE t_id_tab IS TABLE OF forall_test.id%TYPE;
TYPE t_code_tab IS TABLE OF forall_test.code%TYPE;
TYPE t_desc_tab IS TABLE OF forall_test.description%TYPE;
l_id_tab t_id_tab := t_id_tab();
l_code_tab t_code_tab := t_code_tab();
l_desc_tab t_desc_tab := t_desc_tab();
l_start NUMBER;
l_size NUMBER :=
10000;
BEGIN
-- Populate collections.
FOR i IN 1 .. l_size LOOP
l_id_tab.extend;
l_code_tab.extend;
l_desc_tab.extend;
l_id_tab(l_id_tab.last) := i;
l_code_tab(l_code_tab.last) := TO_CHAR(i);
l_desc_tab(l_desc_tab.last) := 'Description: ' || TO_CHAR(i);
END LOOP;
--
Time regular updates.
l_start := DBMS_UTILITY.get_time;
FOR i
IN l_id_tab.first .. l_id_tab.last LOOP
UPDATE forall_test
SET id
= l_id_tab(i),
code
= l_code_tab(i),
description =
l_desc_tab(i)
WHERE id
= l_id_tab(i);
END LOOP;
DBMS_OUTPUT.put_line('Normal Updates : ' ||
(DBMS_UTILITY.get_time - l_start));
l_start := DBMS_UTILITY.get_time;
--
Time bulk updates.
FORALL i IN l_id_tab.first .. l_id_tab.last
UPDATE forall_test
SET id =
l_id_tab(i),
code
= l_code_tab(i),
description =
l_desc_tab(i)
WHERE id
= l_id_tab(i);
DBMS_OUTPUT.put_line('Bulk Updates : ' ||
(DBMS_UTILITY.get_time - l_start));
COMMIT;
END;
/
Once again it is apparent that the bulk
operation is the more efficient of the two.
SQL> @update_forall.sql
Normal Updates : 201
Bulk Updates : 104
PL/SQL procedure successfully completed.
The following section compares the performance
of conventional operations with bulk delete operations.
Bulk DELETE Operations
The bulk delete operation is the same
regardless of server version. Using the forall_test table, a
single predicate is needed in the WHERE clause, but for this example
both the ID and CODE columns are included as if they represented a
concatenated key.
The delete_forall.sql script listed below is
used for this test. The script contains rollback statements,
which are necessary to make sure the bulk operation has something to
delete. Since the script uses separate collections for each
bind, it is suitable for all versions of Oracle that support bulk
operations.
delete_forall.sql
SET
SERVEROUTPUT ON
DECLARE
TYPE t_id_tab IS TABLE OF forall_test.id%TYPE;
TYPE t_code_tab IS TABLE OF forall_test.code%TYPE;
l_id_tab t_id_tab := t_id_tab();
l_code_tab t_code_tab := t_code_tab();
l_start NUMBER;
l_size NUMBER :=
10000;
BEGIN
-- Populate collections.
FOR i IN 1 .. l_size LOOP
l_id_tab.extend;
l_code_tab.extend;
l_id_tab(l_id_tab.last) := i;
l_code_tab(l_code_tab.last) := TO_CHAR(i);
END LOOP;
--
Time regular updates.
l_start := DBMS_UTILITY.get_time;
FOR i
IN l_id_tab.first .. l_id_tab.last LOOP
DELETE FROM forall_test
WHERE id = l_id_tab(i)
AND code = l_code_tab(i);
END LOOP;
ROLLBACK;
DBMS_OUTPUT.put_line('Normal Deletes : ' ||
(DBMS_UTILITY.get_time - l_start));
l_start := DBMS_UTILITY.get_time;
--
Time bulk updates.
FORALL i IN l_id_tab.first .. l_id_tab.last
DELETE FROM forall_test
WHERE id = l_id_tab(i)
AND code = l_code_tab(i);
DBMS_OUTPUT.put_line('Bulk Deletes : ' ||
(DBMS_UTILITY.get_time - l_start));
ROLLBACK;
END;
/
Before running the delete_forall.sql script
make sure the forall_test table is populated using the
insert_forall.sql script or there will be no records to delete.
SQL> @delete_forall.sql
Normal Deletes : 416
Bulk Deletes : 204
PL/SQL
procedure successfully completed.
The performance of the bulk delete is similar
to the performance of the bulk update; the bulk operation is
approximately twice the speed of the conventional operation.
In the next section, methods for handling
sparse collections available in Oracle 10g are presented.
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