在《SQL Tuning 基础概述05 - Oracle 索引类型及介绍》的1.5小节,提到了几种"索引的常见执行计划":

INDEX FULL SCAN:索引的全扫描,单块读,有序
INDEX RANGE SCAN:索引的范围扫描
INDEX FAST FULL SCAN:索引的快速全扫描,多块读,无序
INDEX FULL SCAN(MIN/MAX):针对MAX(),MIN()函数的查询
INDEX SKIP SCAN:查询条件没有用到组合索引的第一列,而组合索引的第一列重复度较高时,可能用到

本文用简单的测试案例,体会下索引使用这些执行计划的场景:

1.准备测试环境

创建测试表和索引:

conn jingyu/jingyu
drop table test_objects;
create table test_objects as select * from all_objects;
create index idx_test_objects_1 on test_objects(owner, object_name, subobject_name);
create index idx_test_objects_2 on test_objects(object_id);

查看测试表结构:

SQL> desc test_objects;
Name Null? Type
----------------------------------------------------------------- -------- --------------------------------------------
OWNER NOT NULL VARCHAR2(30)
OBJECT_NAME NOT NULL VARCHAR2(30)
SUBOBJECT_NAME VARCHAR2(30)
OBJECT_ID NOT NULL NUMBER
DATA_OBJECT_ID NUMBER
OBJECT_TYPE VARCHAR2(19)
CREATED NOT NULL DATE
LAST_DDL_TIME NOT NULL DATE
TIMESTAMP VARCHAR2(19)
STATUS VARCHAR2(7)
TEMPORARY VARCHAR2(1)
GENERATED VARCHAR2(1)
SECONDARY VARCHAR2(1)
NAMESPACE NOT NULL NUMBER
EDITION_NAME VARCHAR2(30)

查看测试表上的索引信息:

SQL> select index_name, column_name, column_position from user_ind_columns where table_name = 'TEST_OBJECTS';

INDEX_NAME                     COLUMN_NAME                              COLUMN_POSITION
------------------------------ ---------------------------------------- ---------------
IDX_TEST_OBJECTS_1 OWNER 1
IDX_TEST_OBJECTS_1 OBJECT_NAME 2
IDX_TEST_OBJECTS_1 SUBOBJECT_NAME 3
IDX_TEST_OBJECTS_2 OBJECT_ID 1

分析表并清空测试环境的shared_pool和buffer_cache:

analyze table test_objects compute statistics;
alter system flush shared_pool;
alter system flush buffer_cache;

2.编写SQL语句

根据不同执行计划的场景,编写SQL语句:

--INDEX RANGE SCAN(索引的范围扫描)
SELECT owner, object_name FROM test_objects WHERE owner = 'SYS' AND object_name = 'DBMS_OUTPUT'; --INDEX SKIP SCAN(针对MAX(),MIN()函数的查询)
SELECT owner, object_name FROM test_objects WHERE object_name = 'DBMS_OUTPUT'; --INDEX FAST FULL SCAN(索引的快速全扫描,多块读,无序)
SELECT owner, object_name FROM test_objects; --INDEX FULL SCAN(索引的全扫描,单块读,有序)
SELECT owner, object_name FROM test_objects order by 1, 2; --INDEX FULL SCAN (MIN/MAX)(针对MAX(),MIN()函数的查询)
SELECT max(object_id) FROM test_objects;

3.实验环境验证

根据2中的SQL分别在实验环境中验证,没有问题,结果如下:

SQL> set autot trace
--1. INDEX RANGE SCAN
SQL> SELECT owner, object_name FROM test_objects WHERE owner = 'SYS' AND object_name = 'DBMS_OUTPUT'; Execution Plan
----------------------------------------------------------
Plan hash value: 3492129186 ---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 29 | 3 (0)| 00:00:01 |
|* 1 | INDEX RANGE SCAN| IDX_TEST_OBJECTS_1 | 1 | 29 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------------------- Predicate Information (identified by operation id):
--------------------------------------------------- 1 - access("OWNER"='SYS' AND "OBJECT_NAME"='DBMS_OUTPUT') Statistics
----------------------------------------------------------
59 recursive calls
0 db block gets
104 consistent gets
17 physical reads
0 redo size
676 bytes sent via SQL*Net to client
519 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
6 sorts (memory)
0 sorts (disk)
2 rows processed --2. INDEX SKIP SCAN
SQL> SELECT owner, object_name FROM test_objects WHERE object_name = 'DBMS_OUTPUT'; Execution Plan
----------------------------------------------------------
Plan hash value: 1228438998 ---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 2 | 58 | 27 (0)| 00:00:01 |
|* 1 | INDEX SKIP SCAN | IDX_TEST_OBJECTS_1 | 2 | 58 | 27 (0)| 00:00:01 |
--------------------------------------------------------------------------------------- Predicate Information (identified by operation id):
--------------------------------------------------- 1 - access("OBJECT_NAME"='DBMS_OUTPUT')
filter("OBJECT_NAME"='DBMS_OUTPUT') Statistics
----------------------------------------------------------
2 recursive calls
0 db block gets
32 consistent gets
23 physical reads
0 redo size
684 bytes sent via SQL*Net to client
519 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
3 rows processed --3. INDEX FAST FULL SCAN
SQL> SELECT owner, object_name FROM test_objects; 84311 rows selected. Execution Plan
----------------------------------------------------------
Plan hash value: 2324984732 -------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 84311 | 387K| 138 (0)| 00:00:02 |
| 1 | INDEX FAST FULL SCAN| IDX_TEST_OBJECTS_1 | 84311 | 387K| 138 (0)| 00:00:02 |
------------------------------------------------------------------------------------------- Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
6097 consistent gets
480 physical reads
0 redo size
3509341 bytes sent via SQL*Net to client
62339 bytes received via SQL*Net from client
5622 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
84311 rows processed --4. INDEX FULL SCAN
SQL> SELECT owner, object_name FROM test_objects order by 1, 2; 84311 rows selected. Execution Plan
----------------------------------------------------------
Plan hash value: 2751381935 ---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 84311 | 387K| 505 (1)| 00:00:07 |
| 1 | INDEX FULL SCAN | IDX_TEST_OBJECTS_1 | 84311 | 387K| 505 (1)| 00:00:07 |
--------------------------------------------------------------------------------------- Statistics
----------------------------------------------------------
1 recursive calls
0 db block gets
6090 consistent gets
0 physical reads
0 redo size
3509341 bytes sent via SQL*Net to client
62339 bytes received via SQL*Net from client
5622 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
84311 rows processed --5. INDEX FULL SCAN (MIN/MAX)
SQL> SELECT max(object_id) FROM test_objects; Execution Plan
----------------------------------------------------------
Plan hash value: 729623451 -------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 4 | 2 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 4 | | |
| 2 | INDEX FULL SCAN (MIN/MAX)| IDX_TEST_OBJECTS_2 | 1 | 4 | 2 (0)| 00:00:01 |
------------------------------------------------------------------------------------------------- Statistics
----------------------------------------------------------
2 recursive calls
0 db block gets
5 consistent gets
2 physical reads
0 redo size
534 bytes sent via SQL*Net to client
519 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

SQL Tuning 基础概述10的更多相关文章

  1. SQL Tuning 基础概述10 - 体会索引的常见执行计划

    在<SQL Tuning 基础概述05 - Oracle 索引类型及介绍>的1.5小节,提到了几种"索引的常见执行计划": INDEX FULL SCAN:索引的全扫描 ...

  2. SQL Tuning 基础概述08 - SQL Tuning Advisor

    SQL调优顾问 SQL Tuning Advisor的使用案例: 1.构建测试表T 2.定义调整任务 3.修改调整任务参数 4.执行调整任务 5.监控调整任务 6.查看调整任务建议 7.删除调整任务 ...

  3. SQL Tuning 基础概述03 - 使用sql_trace和10046事件跟踪执行计划

    1.使用sql_trace跟踪执行计划 1.1 当前session跟踪: alter session set sql_trace = true; //开始sql_trace alter session ...

  4. SQL Tuning 基础概述05 - Oracle 索引类型及介绍

    一.B-Tree索引 三大特点:高度较低.存储列值.结构有序 1.1利用索引特性进行优化 外键上建立索引:不但可以提升查询效率,而且可以有效避免锁的竞争(外键所在表delete记录未提交,主键所在表会 ...

  5. SQL Tuning 基础概述09 - SQL Access Advisor

    Oracle官方文档对SQL Access Advisor的描述如下: SQL Access Advisor, which is a tuning tool that provides advice ...

  6. SQL Tuning 基础概述01 - Autotrace的设定

    1.autotrace的设定 SQL> set autotrace Usage: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [ST ...

  7. SQL Tuning 基础概述02 - Explain plan的使用

    1.explain plan的使用 SQL> explain plan for delete from t_jingyu; Explained. SQL> select * from ta ...

  8. SQL Tuning 基础概述06 - 表的关联方式:Nested Loops Join,Merge Sort Join & Hash Join

    nested loops join(嵌套循环)   驱动表返回几条结果集,被驱动表访问多少次,有驱动顺序,无须排序,无任何限制. 驱动表限制条件有索引,被驱动表连接条件有索引. hints:use_n ...

  9. SQL Tuning 基础概述07 - SQL Joins

    N多年之前,刚刚接触SQL的时候,就被多表查询中的各种内连接,外连接,左外连接,右外连接等各式各样的连接弄的晕头转向. 更坑的是书上看到的各种表连接还有两种不同的写法, 比如对于表A,表B的查询 1, ...

随机推荐

  1. 连接局域网mysql数据库

    1.先确认mysql服务端端口在防火墙是否开放外网连接(添加): windows防火墙 >高级设置 >入站规则 >新建规则 >选择端口 >添加端口 >后面直接下一步 ...

  2. Js 监听器

    在Ajax取数据时,采用$("#id").click(function(){})的方式不能正确设置监听,需要用$("#parent").on("cli ...

  3. 归纳整理Python中的控制流语句的知识点

    归纳整理Python中的控制流语句的知识点 Python 解释器在其最简单的级别,以类似的方式操作,即从程序的顶端开始,然后一行一行地顺序执行程序语句.例如,清单 1 展示了几个简单的语句.当把它们键 ...

  4. Python中第三方库Requests库的高级用法详解

    Python中第三方库Requests库的高级用法详解 虽然Python的标准库中urllib2模块已经包含了平常我们使用的大多数功能,但是它的API使用起来让人实在感觉不好.它已经不适合现在的时代, ...

  5. Books Exchange (easy version)   CodeForces - 1249B2

    The only difference between easy and hard versions is constraints. There are nn kids, each of them i ...

  6. Spring IoC的形象化理解

    1.IoC(控制反转) 首先想说说IoC(Inversion of Control,控制反转).这是spring的核心,贯穿始终.所谓IoC,对于spring框架来说,就是由spring来负责控制对象 ...

  7. 【并行计算-CUDA开发】CUDA并行存储模型

    CUDA并行存储模型 CUDA将CPU作为主机(Host),GPU作为设备(Device).一个系统中可以有一个主机和多个设备.CPU负责逻辑性强的事务处理和串行计算,GPU专注于执行高度线程化的并行 ...

  8. springboot整合es客户端操作elasticsearch(二)

    在上章节中整合elasticsearch客户端出现版本问题进行了处理,这章来进行springboot整合得操作 环境:elaticsearch6.2.1,springboot 2.1.8 客户端版本采 ...

  9. JSP基础知识补充

    <meta http-equiv="Pragma" content="no-cache"><meta http-equiv="Cac ...

  10. 为什么还需要应用层的Keepalive?

    既然TCP有了keepalive,应用层还需要Keepalive多此一举吗? 显然是不是的,首先协议分层思想,每层的关注点不同,TCP属于传输层,关注“通”,应用层关注是否能“用”,能“通”不一定能“ ...