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
• 2.编写SQL语句
• 3.实验环境验证

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 NUMBERDATA_OBJECT_ID                                                             NUMBEROBJECT_TYPE                                                                VARCHAR2(19)CREATED                                                           NOT NULL DATELAST_DDL_TIME                                                     NOT NULL DATETIMESTAMP                                                                  VARCHAR2(19)STATUS                                                                     VARCHAR2(7)TEMPORARY                                                                  VARCHAR2(1)GENERATED                                                                  VARCHAR2(1)SECONDARY                                                                  VARCHAR2(1)NAMESPACE                                                         NOT NULL NUMBEREDITION_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 calls0  db block gets104  consistent gets17  physical reads0  redo size676  bytes sent via SQL*Net to client519  bytes received via SQL*Net from client2  SQL*Net roundtrips to/from client6  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 calls0  db block gets32  consistent gets23  physical reads0  redo size684  bytes sent via SQL*Net to client519  bytes received via SQL*Net from client2  SQL*Net roundtrips to/from client0  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 calls0  db block gets6097  consistent gets480  physical reads0  redo size3509341  bytes sent via SQL*Net to client62339  bytes received via SQL*Net from client5622  SQL*Net roundtrips to/from client0  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 calls0  db block gets6090  consistent gets0  physical reads0  redo size3509341  bytes sent via SQL*Net to client62339  bytes received via SQL*Net from client5622  SQL*Net roundtrips to/from client0  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 calls0  db block gets5  consistent gets2  physical reads0  redo size534  bytes sent via SQL*Net to client519  bytes received via SQL*Net from client2  SQL*Net roundtrips to/from client0  sorts (memory)0  sorts (disk)1  rows processed