oracle中bulk collect into用法
来源:互联网 发布:unity3d ios 编辑:程序博客网 时间:2024/05/18 03:14
通过bulk collect减少loop处理的开销 采用bulk collect可以将查询结果一次性地加载到collections中。 而不是通过cursor一条一条地处理。 可以在select into,fetch into,returning into语句使用bulk collect。 注意在使用bulk collect时,所有的into变量都必须是collections. 举几个简单的例子: --在select into语句中使用bulk collect DECLARE TYPE SalList IS TABLE OF emp.sal%TYPE; sals SalList; BEGIN -- Limit the number of rows to 100. SELECT sal BULK COLLECT INTO sals FROM emp WHERE ROWNUM <= 100; -- Retrieve 10% (approximately) of the rows in the table. SELECT sal BULK COLLECT INTO sals FROM emp SAMPLE 10; END; / --在fetch into中使用bulk collect DECLARE TYPE DeptRecTab IS TABLE OF dept%ROWTYPE; dept_recs DeptRecTab; CURSOR c1 IS SELECT deptno, dname, loc FROM dept WHERE deptno > 10; BEGIN OPEN c1; FETCH c1 BULK COLLECT INTO dept_recs; END; / --在returning into中使用bulk collect CREATE TABLE emp2 AS SELECT * FROM employees; DECLARE TYPE NumList IS TABLE OF employees.employee_id%TYPE; enums NumList; TYPE NameList IS TABLE OF employees.last_name%TYPE; names NameList; BEGIN DELETE FROM emp2 WHERE department_id = 30 RETURNING employee_id, last_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('Employee #' || enums(i) || ': ' || names(i)); END LOOP; END; / DROP TABLE emp2;
http://xuejiangtao.iteye.com/blog/1168570
----------------------------
如果有个大数据量的DML操作事务,在OLAP报表等低并发库里. 并且强制归档模式中.
采用BULK 和FORALL 会比较快!
open cur_COLUMN_USER; loop fetch cur_COLUMN_USER bulk collect into l_ARY_statedate, l_ARY_form, l_ARY_columnid, l_ARY_usernumber, l_ARY_new_user, l_ARY_exit_use limit g_batch_size_n; forall i in 1..l_ARY_statedate.count insert into content_lst_day (......) values(l_ary_statedate(i),....); commit;end loop;相对使用普通游标循环提取数据出来处理的话 会快很多.
原因 1 bulk collect into 到数组 可以一次型把数据提取出来,减少了循环当中PL/SQL和SQL引撑的切换时间
原因 2 forall in ..... 也是一次型提交数据到某个地方 也同样减少了循环当中PL/SQL和SQL引撑的切换时间
注意 1 数据太大 要设置合理的LIMIT 否则提取到数组的数据会爆了PGA的回话内存
原因 3 bulk 内部操作 对insert delete 做了优化 采用批量方法.极大减少了redo 和Undo 使用量.
原因 4 为证明 当一个大数据量的insert 会超级慢,如果分批插入的总时间 比一次插入省很多时间.
An ORA-22813 when using BULK COLLECT is typically expected behavior indicating that you have exceeded the amount of free memory in the PGA. As collections are processed by PL/SQL they use the PGA to store their memory structures. Depending on the LIMIT size of the BULK COLLECT and additional processing of the collected data you may exceed the free memory of the PGA. While intuitively you may think that increasing the PGA memory and increasing the LIMIT size will increase performance, the following example shows you that this is not true in this case. So, by reviewing this example you should be able to strike a balance between a reasonable LIMIT size and the size of the PGA while maintaining a high level of performance using BULK COLLECT.
- oracle中bulk collect into用法
- oracle中bulk collect into用法
- oracle中bulk collect into用法
- oracle中bulk collect into用法
- oracle中bulk collect用法
- oracle bulk collect用法
- oracle 利用bulk collect into 批量insert
- Oracle BULK COLLECT INTO批量操作应用
- 在SELECT INTO中使用BULK COLLECT
- bulk collect into
- bulk collect into集合
- Oracle 中使用 fetch bulk collect into 批量效率的读取游标数据
- Oracle 中使用 fetch bulk collect into 批量效率的读取游标数据【转】
- Oracle 中使用 fetch bulk collect into 批量效率的读取游标数据
- Oracle 中使用 fetch bulk collect into 批量效率的读取游标数据(转载)
- Oracle中使用fetch bulk collect into批量效率的读取
- Oracle 中使用 fetch bulk collect into 批量效率的读取游标数据
- Oracle 中使用 fetch bulk collect into 批量效率的读取
- memcached
- hdu 2222 Keywords Search(AC自动机)
- POJ:3026 Borg Maze
- 使用MFC::CArchive
- sencha touch之表单二(注册页面)
- oracle中bulk collect into用法
- jsp只在首次加载时调用action
- 把Window设置成灰暗
- PHP中htmlentities和htmlspecialchars的区别
- Ganglia集成Nagios组合监视企业集群并设置邮件报警
- skyFS-mapreduce0.5版作业调度分析
- The programming language 习题4-2
- C++调用WebService
- RMAN备份批处理命令 LOG CMDFILE的意思