PLSQL NOTE--------提高性能的BULK COLLECT语句和FORALL语句

 1  CREATE TABLE employees_temp AS SELECT * FROM employees;
 2  DECLARE
 3     TYPE NumList IS VARRAY(20) OF NUMBER;
 4     depts NumList := NumList(10, 30, 70);  -- department numbers
 5  BEGIN
 6     FORALL i IN depts.FIRST..depts.LAST
 7        DELETE FROM employees_temp WHERE department_id = depts(i);
 8     COMMIT;
 9  END;
10  /

 1  CREATE TABLE parts1 (pnum INTEGER, pname VARCHAR2(15));
 2  CREATE TABLE parts2 (pnum INTEGER, pname VARCHAR2(15));
 3  DECLARE
 4    TYPE NumTab IS TABLE OF parts1.pnum%TYPE INDEX BY PLS_INTEGER;
 5    TYPE NameTab IS TABLE OF parts1.pname%TYPE INDEX BY PLS_INTEGER;
 6    pnums  NumTab;
 7    pnames NameTab;
 8    iterations CONSTANT PLS_INTEGER := 500;
 9    t1 INTEGER;
10    t2 INTEGER;
11    t3 INTEGER;
12  BEGIN
13    FOR j IN 1..iterations LOOP  -- load index-by tables
14       pnums(j) := j;
15       pnames(j) := ‘Part No. ‘ || TO_CHAR(j);
16    END LOOP;
17    t1 := DBMS_UTILITY.get_time;
18    FOR i IN 1..iterations LOOP  -- use FOR loop
19       INSERT INTO parts1 VALUES (pnums(i), pnames(i));
20    END LOOP;
21    t2 := DBMS_UTILITY.get_time;
22    FORALL i IN 1..iterations  -- use FORALL statement
23       INSERT INTO parts2 VALUES (pnums(i), pnames(i));
24    t3 := DBMS_UTILITY.get_time;
25    DBMS_OUTPUT.PUT_LINE(‘Execution Time (secs)‘);
26    DBMS_OUTPUT.PUT_LINE(‘---------------------‘);
27    DBMS_OUTPUT.PUT_LINE(‘FOR loop: ‘ || TO_CHAR((t2 - t1)/100));
28    DBMS_OUTPUT.PUT_LINE(‘FORALL:   ‘ || TO_CHAR((t3 - t2)/100));
29    COMMIT;
30  END;
31  /    
32  Execution Time (secs)
33  ---------------------
34  FOR loop: .02
35  FORALL:   0

 1  CREATE TABLE employees_temp AS SELECT * FROM employees;
 2  DECLARE
 3     TYPE NumList IS VARRAY(10) OF NUMBER;
 4     depts NumList := NumList(5,10,20,30,50,55,57,60,70,75);
 5  BEGIN
 6     FORALL j IN 4..7  -- use only part of varray
 7        DELETE FROM employees_temp WHERE department_id = depts(j);
 8     COMMIT;
 9  END;
10  /

 1  -- Create empty tables to hold order details
 2  CREATE TABLE valid_orders (cust_name VARCHAR2(32), amount NUMBER(10,2));
 3  CREATE TABLE big_orders AS SELECT * FROM valid_orders WHERE 1 = 0;
 4  CREATE TABLE rejected_orders AS SELECT * FROM valid_orders WHERE 1 = 0;
 5  DECLARE
 6  -- Make collections to hold a set of customer names and order amounts.
 7     SUBTYPE cust_name IS valid_orders.cust_name%TYPE;
 8     TYPE cust_typ IS TABLE OF cust_name;
 9     cust_tab cust_typ;
10     SUBTYPE order_amount IS valid_orders.amount%TYPE;
11     TYPE amount_typ IS TABLE OF NUMBER;
12     amount_tab amount_typ;
13  -- Make other collections to point into the CUST_TAB collection.
14     TYPE index_pointer_t IS TABLE OF PLS_INTEGER;
15     big_order_tab index_pointer_t := index_pointer_t();
16     rejected_order_tab index_pointer_t := index_pointer_t();
17     PROCEDURE setup_data IS BEGIN
18  -- Set up sample order data, including some invalid orders and some ‘big‘ orders.
19       cust_tab := cust_typ(‘Company1‘,‘Company2‘,‘Company3‘,‘Company4‘,‘Company5‘);
20       amount_tab := amount_typ(5000.01, 0, 150.25, 4000.00, NULL);
21     END;
22  BEGIN
23     setup_data();
24     DBMS_OUTPUT.PUT_LINE(‘--- Original order data ---‘);
25     FOR i IN 1..cust_tab.LAST LOOP
26       DBMS_OUTPUT.PUT_LINE(‘Customer #‘ || i || ‘, ‘ || cust_tab(i) || ‘: $‘ ||
27                             amount_tab(i));
28     END LOOP;
29  -- Delete invalid orders (where amount is null or 0).
30     FOR i IN 1..cust_tab.LAST LOOP
31       IF amount_tab(i) is null or amount_tab(i) = 0 THEN
32          cust_tab.delete(i);
33          amount_tab.delete(i);
34       END IF;
35     END LOOP;
36     DBMS_OUTPUT.PUT_LINE(‘--- Data with invalid orders deleted ---‘);
37     FOR i IN 1..cust_tab.LAST LOOP
38       IF cust_tab.EXISTS(i) THEN
39         DBMS_OUTPUT.PUT_LINE(‘Customer #‘ || i || ‘, ‘ || cust_tab(i) || ‘: $‘ ||
40                               amount_tab(i));
41        END IF;
42     END LOOP;
43  -- Because the subscripts of the collections are not consecutive, use
44  -- FORALL...INDICES OF to iterate through the actual subscripts, 
45  -- rather than 1..COUNT
46     FORALL i IN INDICES OF cust_tab
47       INSERT INTO valid_orders(cust_name, amount) 
48          VALUES(cust_tab(i), amount_tab(i));
49  -- Now process the order data differently
50  -- Extract 2 subsets and store each subset in a different table
51     setup_data(); -- Initialize the CUST_TAB and AMOUNT_TAB collections again.
52     FOR i IN cust_tab.FIRST .. cust_tab.LAST LOOP
53       IF amount_tab(i) IS NULL OR amount_tab(i) = 0 THEN
54         rejected_order_tab.EXTEND; -- Add a new element to this collection
55  -- Record the subscript from the original collection
56         rejected_order_tab(rejected_order_tab.LAST) := i; 
57       END IF;
58       IF amount_tab(i) > 2000 THEN
59          big_order_tab.EXTEND; -- Add a new element to this collection
60  -- Record the subscript from the original collection
61          big_order_tab(big_order_tab.LAST) := i;
62       END IF;
63     END LOOP;
64  -- Now it‘s easy to run one DML statement on one subset of elements, 
65  -- and another DML statement on a different subset.
66     FORALL i IN VALUES OF rejected_order_tab
67       INSERT INTO rejected_orders VALUES (cust_tab(i), amount_tab(i));
68     FORALL i IN VALUES OF big_order_tab
69       INSERT INTO big_orders VALUES (cust_tab(i), amount_tab(i));
70     COMMIT;
71  END;
72  /
73  -- Verify that the correct order details were stored
74  SELECT cust_name "Customer", amount "Valid order amount" FROM valid_orders;
75  SELECT cust_name "Customer", amount "Big order amount" FROM big_orders;
76  SELECT cust_name "Customer", amount "Rejected order amount" FROM rejected_orders;