Bulk Binds对性能的提高

 当Oracle运行PL/SQL时会使用两套引擎，所有procedural code由PL/SQL engine 完成，所有SQL由SQL engine处理。所以如果Oracle从一个collection中循环执行相同的DML操作，那么为了避免两套engine切换所消耗的系统资源，可以使用bulk binds来把所有的DML操作binding到一次操作中完成。这将极大提高PL/SQL的执行效率。

　　以下是简单的测试，用两种方式插入100000条数据，可以看到效率提高了7倍左右。

SQL> CREATE TABLE test1(
2    id           NUMBER(10),
3    description  VARCHAR2(50));
Table created
SQL> ALTER TABLE test1 ADD (
2    CONSTRAINT test1_pk PRIMARY KEY (id));
Table altered
SQL> SET TIMING ON;
SQL> DECLARE
2    TYPE id_type          IS TABLE OF test1.id%TYPE;
3    TYPE description_type IS TABLE OF test1.description%TYPE;
4
5    t_id           id_type          := id_type();
6    t_description  description_type := description_type();
7  BEGIN
8    FOR i IN 1 .. 100000 LOOP
9      t_id.extend;
10      t_description.extend;
11
12      t_id(t_id.last)                   := i;
13      t_description(t_description.last) := 'Description: ' || To_Char(i);
14    END LOOP;
15
16    FOR i IN t_id.first .. t_id.last LOOP
17      INSERT INTO test1 (id, description)
18      VALUES (t_id(i), t_description(i));
19    END LOOP;
20
21    COMMIT;
22  END;
23  /
PL/SQL procedure successfully completed
Executed in 141.233 seconds
SQL> truncate table test1;
Table truncated
Executed in 0.631 seconds
SQL>
SQL> DECLARE
2    TYPE id_type          IS TABLE OF test1.id%TYPE;
3    TYPE description_type IS TABLE OF test1.description%TYPE;
4
5    t_id           id_type          := id_type();
6    t_description  description_type := description_type();
7  BEGIN
8    FOR i IN 1 .. 100000 LOOP
9      t_id.extend;
10      t_description.extend;
11
12      t_id(t_id.last)                   := i;
13      t_description(t_description.last) := 'Description: ' || To_Char(i);
14    END LOOP;
15
16    FORALL i IN t_id.first .. t_id.last
17      INSERT INTO test1 (id, description)
18      VALUES (t_id(i), t_description(i));
19
20    COMMIT;
21  END;
22  /
PL/SQL procedure successfully completed
Executed in 27.52 seconds
SQL> select count(*) from test1;
COUNT(*)
----------
    100000
Executed in 0.04 seconds