最近在做存储过程,procedure,pro c++
好久没有作了有些生疏了。
   FORALL与BULK COLLECT的使用方法:
1.使用FORALL比FOR效率高,因为前者只切换一次上下文,而后者将是在循环次数一样多个上下文间切换。

2.使用BLUK COLLECT一次取出一个数据集合,比用游标条取数据效率高,尤其是在网络不大好的情况下。但BLUK COLLECT需要大量内存。

例子:
create table test_forall ( user_id number(10), user_name varchar2(20));  
create table test_forall ( user_id number(10), user_name varchar2(20));

select into 中使用bulk collect
 
  1. DECLARE  
  2.   TYPE table_forall IS TABLE OF test_forall%ROWTYPE;   
  3.   v_table table_forall;   
  4. BEGIN  
  5.     SELECT mub.user_id,mub.user_name   
  6.          BULK COLLECT INTO v_table   
  7.     FROM mag_user_basic mub   
  8.          WHERE mub.user_id BETWEEN 10000 AND 10100;   
  9.     FORALL idx IN 1..v_table.COUNT  
  10.            INSERT INTO test_forall VALUES v_table(idx);   
  11.            --VALUES(v_table(idx).user_id,v_table(idx).user_name);Error   
  12.            --在PL/SQL中,BULK In-BIND与RECORD,%ROWTYPE是不能在一块使用的,   
  13.            --也就是说,BULK In-BIND只能与简单类型的数组一块使用   
  14.     COMMIT;   
  15.   
  16. EXCEPTION   
  17.     WHEN OTHERS THEN  
  18.         ROLLBACK;   
  19.      
  20. END;  
DECLARE
  TYPE table_forall IS TABLE OF test_forall%ROWTYPE;
  v_table table_forall;
BEGIN
    SELECT mub.user_id,mub.user_name
         BULK COLLECT INTO v_table
    FROM mag_user_basic mub
         WHERE mub.user_id BETWEEN 10000 AND 10100;
    FORALL idx IN 1..v_table.COUNT
           INSERT INTO test_forall VALUES v_table(idx);
           --VALUES(v_table(idx).user_id,v_table(idx).user_name);Error
           --在PL/SQL中,BULK In-BIND与RECORD,%ROWTYPE是不能在一块使用的,
           --也就是说,BULK In-BIND只能与简单类型的数组一块使用
    COMMIT;

EXCEPTION
    WHEN OTHERS THEN
        ROLLBACK;

END;

fetch into 中使用bulk collect
 
  1. DECLARE  
  2.   TYPE table_forall IS TABLE OF test_forall%ROWTYPE;   
  3.   v_table table_forall;      
  4.      
  5.   CURSOR c1 IS  
  6.     SELECT mub.user_id,mub.user_name   
  7.          FROM mag_user_basic mub   
  8.            WHERE mub.user_id BETWEEN 10000 AND 10100;   
  9. BEGIN  
  10.    OPEN c1;   
  11.    --在fetch into中使用bulk collect   
  12.    FETCH c1 BULK COLLECT INTO v_table;   
  13.       
  14.    FORALL idx IN 1..v_table.COUNT  
  15.          INSERT INTO test_forall VALUES v_table(idx);   
  16.     COMMIT;   
  17.   
  18. EXCEPTION   
  19.     WHEN OTHERS THEN  
  20.         ROLLBACK;   
  21. END;  
DECLARE
  TYPE table_forall IS TABLE OF test_forall%ROWTYPE;
  v_table table_forall;

  CURSOR c1 IS
    SELECT mub.user_id,mub.user_name
         FROM mag_user_basic mub
           WHERE mub.user_id BETWEEN 10000 AND 10100;
BEGIN
   OPEN c1;
   --在fetch into中使用bulk collect
   FETCH c1 BULK COLLECT INTO v_table;

   FORALL idx IN 1..v_table.COUNT
         INSERT INTO test_forall VALUES v_table(idx);
    COMMIT;

EXCEPTION
    WHEN OTHERS THEN
        ROLLBACK;
END;

在returning into中使用bulk collect
 
  1. CREATE TABLE test_forall2 AS SELECT * FROM test_forall;   
  2. ----在returning into中使用bulk collect   
  3. DECLARE  
  4.    TYPE IdList IS TABLE OF test_forall.User_Id%TYPE;   
  5.    enums IdList;   
  6.    TYPE NameList IS TABLE OF test_forall.user_name%TYPE;   
  7.    names NameList;   
  8. BEGIN  
  9.    DELETE FROM test_forall2 WHERE user_id = 10100   
  10.         RETURNING user_id, user_name BULK COLLECT INTO enums, names;   
  11.    dbms_output.put_line('Deleted ' || SQL%ROWCOUNT || ' rows:');   
  12.    FOR i IN enums.FIRST .. enums.LAST  
  13.    LOOP   
  14.      dbms_output.put_line('User #' || enums(i) || ': ' || names(i));   
  15.    END LOOP;   
  16.    COMMIT;   
  17.       
  18. EXCEPTION   
  19.     WHEN OTHERS THEN  
  20.         ROLLBACK;   
  21.           
  22. END;  
CREATE TABLE test_forall2 AS SELECT * FROM test_forall;
----在returning into中使用bulk collect
DECLARE
   TYPE IdList IS TABLE OF test_forall.User_Id%TYPE;
   enums IdList;
   TYPE NameList IS TABLE OF test_forall.user_name%TYPE;
   names NameList;
BEGIN
   DELETE FROM test_forall2 WHERE user_id = 10100
        RETURNING user_id, user_name BULK COLLECT INTO enums, names;
   dbms_output.put_line('Deleted ' || SQL%ROWCOUNT || ' rows:');
   FOR i IN enums.FIRST .. enums.LAST
   LOOP
     dbms_output.put_line('User #' || enums(i) || ': ' || names(i));
   END LOOP;
   COMMIT;

EXCEPTION
    WHEN OTHERS THEN
        ROLLBACK;

END;

批量更新中,将for改成forall
 
  1. DECLARE    
  2.     TYPE NumList IS VARRAY(20) OF NUMBER;                                                   
  3.     depts NumList := NumList(10, 30, 70, ...);   
  4.  -- department numbers                       
  5.      BEGIN           
  6.      ...              
  7.        FOR i IN depts.FIRST..depts.LAST  
  8.        LOOP   
  9.        ...   
  10.        --UPDATE statement is sent to the SQL engine    
  11.        -- with each iteration of the FOR loop!   
  12.          UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);   
  13.       END LOOP:    
  14.     END;            
DECLARE
    TYPE NumList IS VARRAY(20) OF NUMBER;
    depts NumList := NumList(10, 30, 70, ...);
 -- department numbers
     BEGIN
     ...
       FOR i IN depts.FIRST..depts.LAST
       LOOP
       ...
       --UPDATE statement is sent to the SQL engine
       -- with each iteration of the FOR loop!
         UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);
      END LOOP:
    END;

 
  1. --UPDATE statement is sent to the SQL engine just once, with the entire nested table   
  2. FORALL i IN depts.FIRST..depts.LAST    
  3.   UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);   
--UPDATE statement is sent to the SQL engine just once, with the entire nested table
FORALL i IN depts.FIRST..depts.LAST
  UPDATE emp SET sal = sal * 1.10 WHERE deptno = depts(i);

To maximize performance, rewrite your programs as follows:
a. If an INSERT, UPDATE, or DELETE statement executes inside a loop and References collection elements, move it into a FORALL statement.
b. If a SELECT INTO, FETCH INTO, or RETURNING INTO clause references a
Collection, incorporate the BULK COLLECT clause.
c. If possible, use host arrays to pass collections back and forth between your Programs and the database server.
d. If the failure of a DML operation on a particular row is not a serious problem,Include the keywords SAVE EXCEPTIONS in the FORALL statement and report Or clean up the errors in a subsequent loop using the %BULK_EXCEPTIONS Attribute.
11-14 03:26
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