Oracle SQL tuning involves optimizing SQL statements for better performance. Key aspects of SQL tuning include identifying SQL statements with high resource consumption or response times using tools like ADDM, AWR, and V$SQL. Statements can then be tuned by gathering accurate optimizer statistics, adjusting the execution plan using hints, rewriting the SQL, or changing indexes and tables. Tuning is done at both the design and execution stages.

1. Oracle SQL Tuning
⼀一天之旅
申建忠(9i/10g/11g OCM)

2. SQL Statements
• DML
• SELECT
• INSERT/UPDATE/DELETE/MERGE
• DDL
• CREATE/ALTER/DROP/TRUNCATE
• DML on Data Dictionary
• DCL
• GRANT/REVOKE
• TCL
• COMMIT/REVOKE/SAVEPOINT

3. SQL Execution Flow
Parse
Execute
Fetch
(Select only)
Server Process
$ sqlplus hr/hr@orcl
SQL> select last_name,salary
from employees
where employee_id=100;
User Process
Instance
Database
Oracle Server
SQL
Shared
Pool
Buffer
Cache
Log
Buffer
DML only
Data
files
LAST_NAME
SALARY
------------------------- ----------
King 24000
Result

4. Row Source Generator
Syntax analysis
Semantic analysis
Query Transformer
Estimator
Plan Generator
Data
Dictionary
Parser
Optimizer
optimizer
statistics
Hash(SQL) Soft Parse
Hard Parse
Parse
Execution Plan
Execution Plan
Execution Plan
Execution Plan
Execution Plan
Execution Plan
Execution Plan
Execution Plan
Shared Pool
(Library Cache)
Server Process

5. 效能問題種類
Performanc
e
OS
DB
Application Code
(SQL) Design &
Architecture
20%
60%
15%
5%

6. Tuning Cost and Benefit
Time
Low
High
Design Development Production
Cost
Benefit

7. Response Time
Throughput
Time
Response time
Wait time
Service time
Response time=Service time+wait time

8. RT Breakdown
User AP Server DB Server Disk
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
Time
Parse
Execute
Physical I/O
Execute
Execute
Fetch
Process User Request
Generate SQL
Process SQL Result
Generate Web Page
Request
Response
Memory
Logical I/O
Firewall
Physical I/O
Execute
T13
T14
Time
Network filter

9. Which SQL need Tune
• SQL敘述句的執⾏行效率達不到之前所設
定的要求。
• Response Time
• 單⼀一SQL敘述句的整體反應時間
• Throughput
• 單位時間裡，同時執⾏行的SQL敘述句數
量

10. Why SQL need Tune
• 執⾏行多餘或無謂的操作
• 不必要的SORT操作
• 不必要的Table Join操作
• 使⽤用不必要的函數
• 發⽣生⼀一些等待事件(Wait event)
• 不必要的等待
• Lock wait

11. OLTP/DW
• OLTP
• 避免Hard Parse
• Response Time
• Throughput
• Index Access
• DW
• 不介意Hard Parse
• Response Time
• Full Table Scan

12. OLTP/DW
A Data Warehouse(DW) is a relational database that is designed for query and analysis rather than
for transaction processing. It usually contains historical data derived from transaction data, but it can
include data from other sources. It separates analysis workload from transaction workload and
enables an organization to consolidate data from several sources.
In addition to a relational database, a data warehouse environment includes an extraction,
transportation, transformation, and loading (ETL) solution, an online analytical processing (OLAP)
engine, client analysis tools, and other applications that manage the process of gathering data and
delivering it to business users.
An Online Transaction Processing (OLTP) systems are characterized by high throughput, many users,
and a mix of DML operations (insert, update, and delete) and queries.

13. Difference between OLTP
and DW
OLTP DW
3rd Normal Form 表格設計 3NF/Star Schema
多 索引 少
多 Join 中
Normalized DB 資料重覆 DeNormalized DB
少
衍⽣生與彙總
資料
多
事先定義 SELECT Ad Hoc
次數多
每次資料量少
DML 次數少
每次資料量⼤大
Response Time⼩小
Throughput⼤大
系統要求 Response Time⼩小

14. OLTP
OLTP
OLTP
External
Source
DML
DML
DML
DML
DML
DML
DML
Extract
Transform
Load
Data
Mart
Data
Mart
Data
Mart
Data Warehouse
OLAP
BI
Ad
Hoc
Query
Report
Operational
Data Source
OLTP與DW的關聯

15. SQL Tuning on 設計階段
• 在OLTP環境下，可以考慮在WHERE⼦子句
中，使⽤用BindVariable取代Literal，以避免
過多的Hard Parse。
• 避免Table與View進⾏行 Join，以避免產⽣生
Cartesian Join。
• 使⽤用命名規則，以增加SQL的可讀性與
可維護性。
• 指令的⼤大⼩小寫、注解的使⽤用
• 使⽤用Hint前，需要審慎評估。

16. Hard Parse - 1
SQL> select count(*) from hr.emp where job_id='SA_REP';
COUNT(*)
----------
30
SQL> select count(*) from hr.emp where JOB_ID='SA_REP';
COUNT(*)
----------
30
SQL> select sql_id,hash_value,plan_hash_value,executions,sql_text
2 from v$sql
3 where sql_text like 'select count(*) from hr.emp where %';
SQL_ID HASH_VALUE PLAN_HASH_VALUE EXECUTIONS
------------- ---------- --------------- ----------
SQL_TEXT
--------------------------------------------------------------------------------------
8rtytfkcsw4wd 2576225165 2083865914 1
select count(*) from hr.emp where job_id='SA_REP'
asax0q4n558hw 676504092 2083865914 1
select count(*) from hr.emp where JOB_ID='SA_REP'

17. Hard Parse-2
SQL> select count(*) from hr.emp --在hr.emp之後有⼀一個不可⾒見字元n
2 where job_id='SA_REP';
COUNT(*)
----------
30
SQL> SELECT sql_id,hash_value,executions,plan_hash_value,sql_text
2 FROM v$sql
3 WHERE sql_text like 'select count(*) from hr.emp where %';
SQL_ID HASH_VALUE PLAN_HASH_VALUE EXECUTIONS
------------- ---------- --------------- ----------
SQL_TEXT
--------------------------------------------------------------------------------
8rtytfkcsw4wd 2576225165 2083865914 1
select count(*) from hr.emp where job_id='SA_REP'
asax0q4n558hw 676504092 2083865914 1
select count(*) from hr.emp where JOB_ID='SA_REP'
0v9928mstgq0g 4053260303 2083865914 1
select count(*) from hr.emp where job_id='SA_REP'

18. Hard Parse - 3
SQL> select last_name from hr.employees where employee_id=100;
LAST_NAME
-------------------------
King
SQL> select last_name from hr.employees where employee_id=200;
LAST_NAME
-------------------------
Whalen
SQL> SELECT hash_value,plan_hash_value,executions,sql_text
2 FROM v$sql
3 WHERE sql_text like 'select last_name from hr.employees where employee_id=%';
HASH_VALUE PLAN_HASH_VALUE EXECUTIONS
---------- --------------- ----------
SQL_TEXT
------------------------------------------------------------------------------------
2627784799 1833546154 1
select last_name from hr.employees where employee_id=200
280342537 1833546154 1
select last_name from hr.employees where employee_id=100

19. Hard Parse - 4
SQL> variable empid number --此⽅方式僅適⽤用在sqlplus,sql developer等.不過java/NET也有類似語法
SQL> execute :empid := 101;
SQL> select last_name from hr.employees where employee_id=:empid;
LAST_NAME
-------------------------
Kochhar
SQL> execute :empid := 201;
SQL> select last_name from hr.employees where employee_id=:empid;
LAST_NAME
-------------------------
Hartstein
SQL> SELECT hash_value,plan_hash_value,executions sql_text
2 FROM v$sql
3 WHERE sql_text like 'select last_name from hr.employees where employee_id=%'
HASH_VALUE PLAN_HASH_VALUE EXECUTIONS
---------- --------------- ----------
SQL_TEXT
----------------------------------------------------------------------------------------------
476476418 1833546154 2
select last_name from hr.employees where employee_id=:empid
2627784799 1833546154 1
select last_name from hr.employees where employee_id=200
280342537 1833546154 1
select last_name from hr.employees where employee_id=100

20. SQL Tuning on 執⾏行階段
Response time=CPU time+Wait time
必要的CPU time+
不必要的CPU time
必要的Wait time+
不必要的Wait time

21. Which SQL were High Loading ?
• ADDM Report
• AWR Report(Enterprise Edition)
• STATSPACK(Standard Edition)
• V$SQL

22. ADDM

23. AWR Report1

24. AWR Report2

25. Resource V$SQL
Response Time ELAPSED_TIME
Service Time CPU_TIME
Sort SORTS
Total I/Os BUFFER_GETS
Physical I/Os DISK_READS
Row Processed ROW_PROCESSED
Memory RUNTIME_MEMORY
Executions EXECUTIONS
Critical Resources

26. V$SQL
SQL> SELECT *
2 FROM
3 (SELECT sql_id,elapsed_time,cpu_time,buffer_gets,disk_reads,executions
4 FROM v$sql
5 ORDER BY elapsed_time DESC,cpu_time DESC,
6 buffer_gets DESC,disk_reads DESC,executions DESC)
7 WHERE ROWNUM<=10;
SQL_ID ELAPSED_TIME CPU_TIME BUFFER_GETS DISK_READS EXECUTIONS
------------- ------------ ---------- ----------- ---------- ----------
6qyqqyg14bm17 4722430672 4566883727 1171553448 1169941510 1
0a59tkkpx31vx 57267687 52511021 6414812 895 7
cj8ytxm5hhm4y 82778799 83355256 105 1 10100000
01uy9sb7w8a9g 37054402 41994 714 83 1
cvn54b7yz0s8u 25761776 942843 47660 6616 4142
3ktacv9r56b51 18381236 1381807 109780 1048 6350
39m4sx9k63ba2 15383617 449923 22739 1635 4142
ga9j9xk5cy9s0 14530703 493937 24296 752 4142
c6awqs517jpj0 9019830 340949 13858 512 4142
8swypbbr0m372 7280083 802874 100473 764 6350
10 rows selected.

27. V$SQL_MONITOR
SQL> SELECT *
2 FROM
3 (SELECT sql_id,elapsed_time,cpu_time,queuing_time,buffer_gets,disk_reads
4 FROM v$sql_monitor
5 ORDER BY elapsed_time DESC,cpu_time DESC,queuing_time DESC
6 buffer_gets DESC,disk_reads DESC)
7 WHERE ROWNUM<=10;
SQL_ID ELAPSED_TIME CPU_TIME QUEUING_TIME BUFFER_GETS DISK_READS
------------- ------------ ---------- ------------ ----------- ----------
6qyqqyg14bm17 5396549468 5221542205 0 1337837043 17458050
ak3huf5xbg5f6 313934168 304642686 0 48 0
05s9358mm6vrr 14956086 5728129 0 195423 1744
6gvch1xu9ca3g 12560842 1741735 0 44884 1441
0a59tkkpx31vx 11246557 9412567 0 1111033 324
0a59tkkpx31vx 9080340 7986787 0 889924 494
0a59tkkpx31vx 8483972 7845806 0 886621 0
5zruc4v6y32f9 8478735 2486622 0 312062 2210
0a59tkkpx31vx 8175980 7829809 0 890517 0
f6cz4n8y72xdc 7293541 1506770 0 54905 636
10 rows selected.

28. 找出有問題的SQL
相關table/index的
statistics是否正確
⺫⽬目前的執⾏行計劃是
否不需要調整
調整後執⾏行計劃是
否⽐比之前更好
收集相關statistics
調整執⾏行計劃
調整執⾏行計劃之外的相關結構
完成SQL調校
平⾏行處理 使⽤用分區 改寫SQL
No
No
No
Yes
Yes
Yes
建⽴立索引 建⽴立實體化視觀表

29. Optimizer Statistics
TABLE
NUM_ROWS
BLOCKS
AVG_ROW_LEN
STALE_STATS
INDEX
BELVEL
LEAF_BLOCKS
CLUSTERING_FACTOR
DISTINCT_KEYS
AVG_LEAF_BLOCKS_PER_KEY
AVG_DATA_BLOCKS_PER_KEY
NUM_ROWS
COLUMN
NUM_DISTINCT
LOW_VALUE
HIGH_VALUE
NUM_NULLS
DENSITY
NUM_BUCKETS
HISTOGRAM
*_TAB_STATISTICS
*_IND_STATISTICS
*_TAB_COL_STATISTICS

30. Empty/Stale Statistics
SQL> SELECT num_rows,blocks,avg_row_len,stale_stats
2 FROM dba_tab_statistics
3 WHERE owner='HR' and table_name='EMP';
NUM_ROWS BLOCKS AVG_ROW_LEN STA
---------- ---------- ----------- ---
SQL> SELECT num_rows,blocks,avg_row_len,stale_stats
2 FROM dba_tab_statistics
3 WHERE owner='HR' and table_name='EMP';
NUM_ROWS BLOCKS AVG_ROW_LEN STA
---------- ---------- ----------- ---
70 5 69 YES 變動量超過10%
SQL> SELECT COUNT(*) FROM hr.emp;
COUNT(*)
----------
107
Staled statistics
Empty statistics

31. Manual Gather Statistics
SQL> EXECUTE DBMS_STATS.GATHER_TABLE_STATS('HR','EMP');
SQL> SELECT num_rows,blocks,avg_row_len,stale_stats
2 FROM dba_tab_statistics
3 WHERE owner='HR' and table_name='EMP';
NUM_ROWS BLOCKS AVG_ROW_LEN STA
---------- ---------- ----------- ---
107 5 69 NO
SQL> EXECUTE DBMS_STATS.GATHER_SCHEMA_STATS('HR');
SQL> EXECUTE DBMS_STATS.GATHER_DATABASE_STATS;
SQL> EXECUTE DBMS_STATS.GATHER_DICTIONARY_STATS;
SQL> EXECUTE DBMS_STATS.GATHER_FIXED_OBJECT_STATS;

32. Gather Statistics Options
• Estimate Percentage
• Invalidate Execution Plan
• Stale Percentage
• Pending Publish
SQL> DESC dba_tab_stat_prefs
Name Null? Type
----------------------------------- -------- ----------------------------
OWNER NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
PREFERENCE_NAME VARCHAR2(30)
PREFERENCE_VALUE VARCHAR2(1000)

34. Finding Execution Plan
• EXPLAIN PLAN(PLAN_TABLE)
• AUTOTRACE(PLAN_TABLE)
• Shared Pool:Library Cache(V$SQL_PLAN)
• AWR(DBA_HIST_SQL_PLAN)
• SQL Tuning Set
• SQL Plan Baseline
• Tracefile
• EVENT:10046/10053

35. Display Execution Plan
• DBMS_XPLAN.DISPLAY
• DBMS_XPLAN.DISPLAY_CURSOR
• DBMS_XPLAN.DISPLAY_AWR
• DBMS_XPLAN.DISPLAY_SQLSET
• DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE
• SET AUTOTRACE ON
• DBMS_SQLTUNE.REPORT_SQL_MONITOR

36. EXPLAIN PLAN
SQL> EXPLAIN PLAN SET STATEMENT_ID='frank_demo1' FOR
2 SELECT last_name,salary FROM hr.emp WHERE employee_id=100;
Explained.
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY(statement_id=>'frank_demo1'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 3 (0)| 00:00:01|
|* 1 | TABLE ACCESS FULL | EMP | 1 | 16 | 3 (0)| 00:00:01|
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("EMPLOYEE_ID"=100)

37. AUTOTRACE
SQL> SET AUTOTRACE ON
SQL> SELECT last_name,salary FROM hr.emp WHERE employee_id=100;
LAST_NAME SALARY
------------------------- ----------
King 24000
Execution Plan
----------------------------------------------------------
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 16 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 16 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("EMPLOYEE_ID"=100)

38. V$SQL_PLAN
SQL> SELECT sql_id,child_number
2 FROM v$sql
3 WHERE sql_text='SELECT last_name,salary FROM hr.emp WHERE employee_id=100';
SQL_ID CHILD_NUMBER
------------- ------------
cj8ytxm5hhm4y 0
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR('cj8ytxm5hhm4y',0));
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------
SQL_ID cj8ytxm5hhm4y, child number 0
-------------------------------------
SELECT last_name,salary FROM hr.emp WHERE employee_id=100
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 3 (100)| |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 16 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("EMPLOYEE_ID"=100)

39. AWR
SQL> SELECT sql_id
2 FROM dba_hist_sqltext
3 WHERE sql_text='SELECT last_name,salary FROM hr.emp WHERE employee_id=100';
SQL_ID
-------------
cj8ytxm5hhm4y
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_AWR('cj8ytxm5hhm4y'));
PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------
SQL_ID cj8ytxm5hhm4y, child number 0
-------------------------------------
SELECT last_name,salary FROM hr.emp WHERE employee_id=100
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 3 (100)| |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 16 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("EMPLOYEE_ID"=100)

40. SQL Tracefile(RAW)
SQL> ALTER SESSION SET EVENTS '10046 TRACE NAME CONTEXT FOREVER,LEVEL 8';
SQL> SELECT last_name,salary FROM hr.emp WHERE employee_id=100;
LAST_NAME SALARY
------------------------- ----------
King 24000
SQL> ALTER SESSION SET EVENTS '10046 TRACE NAME CONTEXT OFF';
orcl_ora_15492.trc
=====================
PARSING IN CURSOR #140636401352696 len=57 dep=0 uid=0 oct=3 lid=0 tim=1357281071350293 hv=3406318750 ad='78fb4328' sqlid='cj8ytxm5hhm4y'
SELECT last_name,salary FROM hr.emp WHERE employee_id=100
END OF STMT
PARSE #140636401352696:c=20997,e=161413,p=3,cr=138,cu=0,mis=1,r=0,dep=0,og=1,plh=3956160932,tim=1357281071350286
EXEC #140636401352696:c=0,e=98,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=3956160932,tim=1357281071350483
WAIT #140636401352696: nam='SQL*Net message to client' ela= 4 driver id=1413697536 #bytes=1 p3=0 obj#=-1 tim=1357281071350537
FETCH #140636401352696:c=0,e=76,p=0,cr=2,cu=0,mis=0,r=1,dep=0,og=1,plh=3956160932,tim=1357281071350647
WAIT #140636401352696: nam='SQL*Net message from client' ela= 5227 driver id=1413697536 #bytes=1 p3=0 obj#=-1 tim=1357281071355930
FETCH #140636401352696:c=0,e=48,p=0,cr=2,cu=0,mis=0,r=0,dep=0,og=1,plh=3956160932,tim=1357281071356062
STAT #140636401352696 id=1 cnt=1 pid=0 pos=1 obj=77179 op='TABLE ACCESS FULL EMP (cr=4 pr=0 pw=0 time=118 us cost=3 size=16 card=1)'
WAIT #140636401352696: nam='SQL*Net message to client' ela= 3 driver id=1413697536 #bytes=1 p3=0 obj#=-1 tim=1357281071356153
$ tkprof orcl_ora_15492.trc output1.txt

41. SQL ID: cj8ytxm5hhm4y Plan Hash: 3956160932
SELECT last_name,salary
FROM
hr.emp WHERE employee_id=100
call count cpu elapsed disk query current rows
----------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.04 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2 0.00 0.00 0 4 0 1
----------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 0.00 0.04 0 4 0 1
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: SYS
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max) Row Source Operation
---------- ---------- ---------- ---------------------------------------------------
1 1 1 TABLE ACCESS FULL EMP (cr=4 pr=0 pw=0 time=118 us cost=3 size=16 card=1)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 17.86 17.87

42. 10053 Trace
SQL> SELECT sql_id
2 FROM dba_hist_sqltext
3 WHERE sql_text='SELECT last_name,salary FROM hr.emp WHERE employee_id=100';
SQL_ID
-------------
cj8ytxm5hhm4y
SQL> EXECUTE dbms_sqldiag.dump_trace(
2> p_sql_id=>'3jb04z19uj8jf',
3> p_child_number=>0,
4> p_component=>'Compiler',
5> p_file_id=>'Hello_frank');
SQL> SELECT value FROM v$diag_info WHERE name='Default Trace File';
VALUE
-------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_3704_Hello_frank.trc

43. 10053 Trace Content
============
Plan Table
============
-------------------------------------+-----------------------------------+
| Id | Operation | Name | Rows | Bytes | Cost | Time |
-------------------------------------+-----------------------------------+
| 0 | SELECT STATEMENT | | | | 3 | |
| 1 | TABLE ACCESS FULL | EMP | 1 | 40 | 3 | 00:00:01 |
-------------------------------------+-----------------------------------+
Predicate Information:
----------------------
1 - filter("EMPLOYEE_ID"=100)

44. V$SQL_MONITOR
SQL> set pagesize 0 echo off timing off
SQL> set linesize 1000 trimspool on trim on
SQL> set long 2000000 longchunksize 2000000 feedback off
SQL> spool sqlmonrpt_6qyqqyg14bm17.html
SQL> SELECT DBMS_SQLTUNE.REPORT_SQL_MONITOR(type=>’EM’,sql_id=>’6qyqqyg14bm17’) FROM dual;
SQL> spool off

45. 執⾏行計劃
---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 370M(100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | NESTED LOOPS | | 5557 | 94469 | 370M (1)|999:59:59 |
| 3 | TABLE ACCESS FULL| SALES | 918K| 4486K| 1233 (1)| 00:00:15 |
|* 4 | TABLE ACCESS FULL| CUSTOMERS | 1 | 12 | 403 (1)| 00:00:05 |
---------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - filter(("C"."CUST_FIRST_NAME"='Dina' AND
"S"."CUST_ID"="C"."CUST_ID"))
3 4
2
1
SELECT COUNT(*)
FROM frank.sales s,frank.customers c
WHERE s.cust_id=c.cust_id AND c.cust_first_name=‘Dina’

46. • Data Access Method
• Join Order
• Join Method
• 每個Row Source應該盡可能減少傳給下
⼀一個Row Source的資料量
執⾏行計劃的調整順序

47. Data Access Method
使⽤用者提供rowid Table Access By User Rowid
讀取所有位在High Water
Mark之下的Table blocks。
Table Access Full
先透過Index找到某些rows
的ROWID，然後讀取
ROWID所指向的table
blocks。
Index Range Scan
Index Unique Scan
Index Full Scan
Index Fast Full Scan
Index Skip Scan

48. ROWID
rowid為row的相對位置資訊
rowid顯⽰示為18 characters(A-Z,a-z,0-9,+,/共64個character編碼)
ABCDEFGHIJ K L M N O P Q R S T U V W X Y Z a b c d e f g....
0123456789 1011121314151617181920212223242526272829303132....
前6個character表⽰示為segment id(data object id)
前3個character表⽰示為relative file id(row位在哪個datafile之上)
前6個character表⽰示為block id(row位在哪個block之上)
前3個character表⽰示為row number(該block的第幾筆row)
SQL> SELECT dbms_rowid.rowid_object('AAASYtAAEAAAAKnABI') data_object_id,
2 dbms_rowid.rowid_relative_fno('AAASYtAAEAAAAKnABI') relative_file_number,
3 dbms_rowid.rowid_block_number('AAASYtAAEAAAAKnABI') block_number,
4 dbms_rowid.rowid_row_number('AAASYtAAEAAAAKnABI') row_number
5 FROm dual;
DATA_OBJECT_ID RELATIVE_FILE_NUMBER BLOCK_NUMBER ROW_NUMBER
-------------- -------------------- ------------ ----------
75309 4 679 72

49. 1 A A1
10 J J10
17 Q
Q
2 B B2
19 S S19
3 C C3
7 G G7
11 K
K
4 D D4
12 L
L
21 U
U
6 F F6
13 M
M
22 V
V
8 H H8
15 O
O
24 X
X
5 E E5
14 N
N
23 W W23
9 I I9
16 P
P
20 T
T
18 R R18
Table Access By User Rowid

50. Table Access By User Rowid
SQL> SELECT object_id,object_name
2> FROM hr.big1
3> WHERE rowid='AAASYtAAEAAAAKnABI';
OBJECT_ID OBJECT_NAME
---------- ------------------------------
12345 ALERT_QUE_N
------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 42 | 1 (0)| 00:00
|* 1 | TABLE ACCESS BY USER ROWID| BIG1 | 1 | 42 | 1 (0)| 00:00
------------------------------------------------------------------------------

51. Full Table Scan
1 A A1
10 J J10
17 Q
Q
2 B B2
19 S S19
3 C C3
7 G G7
11 K
K
4 D D4
12 L
L
21 U
U
6 F F6
13 M
M
22 V
V
8 H H8
15 O
O
24 X
X
5 E E5
14 N
N
23 W W23
9 I I9
16 P
P
20 T
T
18 R R18

52. Full Table Scan
SQL> SELECT rowid,object_id,object_name
2> FROM hr.big1
3> WHERE object_id=12345;
ROWID OBJECT_ID OBJECT_NAME
------------------ ---------- ------------------------------
AAASYtAAEAAAAKnABI 12345 ALERT_QUE_N
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 30 | 289 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| BIG1 | 1 | 30 | 289 (1)| 00:00:04 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("OBJECT_ID"=12345)

53. Index Unique Scan
branch branch
root
1 rowid
2 rowid
3 rowid
4 rowid
5 rowid
6 rowid
7 rowid
8 rowid
9 rowid
10 rowid
11 rowid
12 rowid
13 rowid
14 rowid
15 rowid
16 rowid
17 rowid
18 rowid
19 rowid
20 rowid
21 rowid
22 rowid
23 rowid
24 rowid
1 A A1
10 J J10
17 Q
Q
2 B B2
19 S S19
3 C C3
7 G G7
11 K
K
4 D D4
12 L
L
21 U
U
6 F F6
13 M
M
22 V
V
8 H H8
15 O
O
24 X
X
5 E E5
14 N
N
23 W W23
9 I I9
16 P
P
20 T
T
18 R R18

54. Index Unique Scan
SQL> SELECT rowid,object_id,object_name
2> FROM hr.big1
3> WHERE object_id=12345;
ROWID OBJECT_ID OBJECT_NAME
------------------ ---------- ------------------------------
AAASYtAAEAAAAKnABI 12345 ALERT_QUE_N
-----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 42 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| BIG1 | 1 | 42 | 2 (0)| 00:00:01 |
|* 2 | INDEX UNIQUE SCAN | BIG1_IDX1 | 1 | | 1 (0)| 00:00:01
| ----------------------------------------------------------------------------------------
-
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=12345)

55. Index Range Scan
Root
branch branch
1 rowid
2 rowid
3 rowid
4 rowid
5 rowid
6 rowid
7 rowid
8 rowid
9 rowid
10 rowid
11 rowid
12 rowid
13 rowid
14 rowid
15 rowid
16 rowid
17 rowid
18 rowid
19 rowid
20 rowid
21 rowid
22 rowid
23 rowid
24 rowid
6 F F6
13 M
M
22 V
V
8 H H8
15 O
O
24 X
X
5 E E5
14 N
N
23 W W23
9 I I9
16 P
P
20 T
T
1 A A1
10 J J10
17 Q
Q
2 B B2
19 S S19
3 C C3
7 G G7
11 K
K
4 D D4
12 L
L
21 U
U
18 R R18

56. Index Range Scan
SQL> SELECT rowid,object_id,object_name
2> FROM hr.big1
3> WHERE object_id=12345;
ROWID OBJECT_ID OBJECT_NAME
------------------ ---------- ------------------------------
AAASYtAAEAAAAKnABI 12345 ALERT_QUE_N
-----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 42 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| BIG1 | 1 | 42 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | BIG1_IDX1 | 1 | | 1 (0)| 00:00:01
| ----------------------------------------------------------------------------------------
-
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=12345)

57. Index Full Scan
branch branch
root
1 rowid
2 rowid
3 rowid
4 rowid
5 rowid
6 rowid
7 rowid
8 rowid
9 rowid
10 rowid
11 rowid
12 rowid
13 rowid
14 rowid
15 rowid
16 rowid
17 rowid
18 rowid
19 rowid
20 rowid
21 rowid
22 rowid
23 rowid
24 rowid

58. Index Full Scan
SQL> select object_id from hr.big1 order by object_id;
OBJECT_ID
---------
2
3
4
5
--其餘省略
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 72476 | 353K| 42 (0)| 00:00:01 |
| 1 | INDEX FULL SCAN | BIG1_IDX1 | 72476 | 353K| 42 (0)| 00:00:01 |
-----------------------------------------------------------------------------------

59. Index Fast Full Scan
branch branch
root
1 rowid
2 rowid
3 rowid
4 rowid
5 rowid
6 rowid
7 rowid
8 rowid
9 rowid
10 rowid
11 rowid
12 rowid
13 rowid
14 rowid
15 rowid
16 rowid
17 rowid
18 rowid
19 rowid
20 rowid
21 rowid
22 rowid
23 rowid
24 rowid
root
1 rowid
2 rowid
3 rowid
4 rowid
5 rowid
6 rowid
7 rowid
8 rowid
9 rowid
10 rowid
11 rowid
12 rowid
branch
22 rowid
23 rowid
24 rowid
16 rowid
17 rowid
18 rowid
13 rowid
14 rowid
15 rowid
branch

60. Index Fast Full Scan
SQL> select object_id from hr.big1;
OBJECT_ID
---------
23456
12345
45678
34567
--其餘省略
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 72476 | 353K| 42 (0)| 00:00:01 |
| 1 | INDEX FAST FULL SCAN| BIG1_IDX1 | 72476 | 353K| 42 (0)| 00:00:01 |
-----------------------------------------------------------------------------------

61. Table Join Method
• Nested Loop Join
• Sort Merge Join
• Hash Join
• Cartesian Join

62. Table Join Order
• ⼀一次Join操作只能結合兩個tables
• 如果有4個table需要join
• 則可能出現4!=24 join order
• 盡量讓最⼩小的兩個table先進⾏行結合

63. A B
1 11
3 33
2 22
Nested Loop Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
A B C D
3 33 33 10
1 11 11 40
1 11 11 50
2 22 22 60
FROM t1 JOIN t2 ON (t1.b=t2.c);
t1 t2

64. A B
1 11
3 33
2 22
Sort Merge Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
t1
t2
A B
1 11
2 22
3 33
C D
11 40
11 50
22 60
33 10
44 20
55 30
A B C D
1 11 11 40
1 11 11 50
2 22 22 60
3 33 33 10
FROM t1 JOIN t2 ON (t1.b=t2.c);
sort
sort

65. A B C D
1 11 11 40
1 11 11 50
2 22 22 60
3 33 33 10
A B
1 11
3 33
2 22
Hash Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 JOIN t2 ON (t1.b=t2.c);
t1
t2
33
11
22
hash_area_size
Build
hash
table
Probing
hash
table1
2
3

66. A B
1 11
3 33
2 22
Cross Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 CROSS JOIN t2;
t1 t2
A B C D
1 11 33 10
1 11 44 20
1 11 55 30
1 11 11 40
1 11 11 50
1 11 22 60
3 33 33 10
3 33 44 20
3 33 55 30
3 33 11 40
3 33 11 50
3 33 22 60
2 22 33 10
2 22 44 20
2 22 55 30
2 22 11 40
2 22 11 50
2 22 22 60

67. A B
1 11
3 33
2 22
4 66
Inner Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 JOIN t2
ON (t1.B=t2.C)
t1 t2
A B C D
1 11 11 40
1 11 11 50
3 33 33 10
2 22 22 60

68. A B
1 11
3 33
2 22
4 66
Left Outer Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 LEFT OUTER JOIN t2
ON (t1.B=t2.C)
t1 t2
A B C D
1 11 11 40
1 11 11 50
3 33 33 10
2 22 22 60
4 66

69. A B
1 11
3 33
2 22
4 66
Right Outer Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 RIGHT OUTER JOIN t2
ON (t1.B=t2.C)
t1 t2
A B C D
1 11 11 40
1 11 11 50
3 33 33 10
2 22 22 60
44 20
55 30

70. A B
1 11
3 33
2 22
4 66
Full Outer Join
C D
33 10
44 20
55 30
11 40
11 50
22 60
FROM t1 FULL OUTER JOIN t2
ON (t1.B=t2.C)
t1 t2
A B C D
1 11 11 40
1 11 11 50
3 33 33 10
2 22 22 60
4 66
44 20
55 30

71. ---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 370M(100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | NESTED LOOPS | | 5557 | 94469 | 370M (1)|999:59:59 |
| 3 | TABLE ACCESS FULL| SALES | 918K| 4486K| 1233 (1)| 00:00:15 |
|* 4 | TABLE ACCESS FULL| CUSTOMERS | 1 | 12 | 403 (1)| 00:00:05 |
---------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - filter(("C"."CUST_FIRST_NAME"='Dina' AND
"S"."CUST_ID"="C"."CUST_ID"))
解析執⾏行計劃
Data Access
Method
Join Method
Join Order
(SALES為driving table)
3 4
2
1
SELECT COUNT(*)
FROM frank.sales s,frank.customers c
WHERE s.cust_id=c.cust_id AND c.cust_first_name=‘Dina’

72. ---------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows| Bytes |Cost (%CPU)|Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 6436K(100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | NESTED LOOPS | | | | | |
| 3 | NESTED LOOPS | |5557 | 94469 | 6436K (1)|21:27:13 |
| 4 | TABLE ACCESS FULL | SALES | 918K| 4486K| 1233 (1)|00:00:15 |
|* 5 | INDEX RANGE SCAN | CUST_FNAME_IDX |1 | | 1 (0)|00:00:01 |
|* 6 | TABLE ACCESS BY INDEX ROWID| CUSTOMERS | 1 | 12 | 2 (0)|00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("C"."CUST_FIRST_NAME"='Dina')
6 - filter("S"."CUST_ID"="C"."CUST_ID")
建⽴立index在WERE⼦子句
存取customers的⽅方法
由Full Table Scan改為
Index Scan
Cost由
370M降到
6
1
2
3
4 5
Time由999:59:59
降為21:27:13

73. --------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows| Bytes|Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | |6435K(100) | |
| 1 | SORT AGGREGATE | | 1 | 17| | |
| 2 | NESTED LOOPS | | | | | |
| 3 | NESTED LOOPS | |5557 | 94469|6435K (1) | 21:27:05 |
| 4 | INDEX FAST FULL SCAN | SALES_CUSTID_IDX| 918K| 4486K| 535 (2) | 00:00:07 |
|* 5 | INDEX RANGE SCAN | CUST_FNAME_IDX | 1 | | 1 (0) | 00:00:01 |
|* 6 | TABLE ACCESS BY INDEX ROWID| CUSTOMERS | 1 | 12| 2 (0) | 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("C"."CUST_FIRST_NAME"='Dina')
6 - filter("S"."CUST_ID"="C"."CUST_ID")
建⽴立index在JOIN⼦子句
Cost由6436K降
到6435K
Time由21:27:43
降為21:27:05
6
1
2
3
4 5

74. --------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows| Bytes|Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | |1838K(100) | |
| 1 | SORT AGGREGATE | | 1 | 17| | |
| 2 | NESTED LOOPS | | | | | |
| 3 | NESTED LOOPS | |5557 | 94469|1838K (1) | 06:07:47 |
| 4 | INDEX FAST FULL SCAN | SALES_CUSTID_IDX| 918K| 4486K| 535 (2) | 00:00:07 |
|* 5 | INDEX RANGE SCAN | CUST_CUSTID_IDX | 1 | | 1 (0) | 00:00:01 |
|* 6 | TABLE ACCESS BY INDEX ROWID| CUSTOMERS | 1 | 12| 2 (0) | 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("S"."CUST_ID"="C"."CUST_ID")
6 - filter("C"."CUST_FIRST_NAME"='Dina')
建⽴立index在JOIN⼦子句
Cost由6436K降
到1838K
Time由21:27:43
降為06:07:47
6
1
2
3
4 5
不使⽤用CUST_FNAME_IDX

75. ---------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | |54544 (100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | NESTED LOOPS | | 5557 | 94469 |54544 (1)| 00:10:55|
|* 3 | TABLE ACCESS BY INDEX ROWID|CUSTOMERS | 43 | 516 |54489 (1)| 00:10:54|
| 4 | INDEX FULL SCAN |CUST_CUSTID_IDX |55500 | | 125 (1)| 00:00:02|
|* 5 | INDEX RANGE SCAN |SALES_CUSTID_IDX| 130 | 650 | 2 (0)| 00:00:01|
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("C"."CUST_FIRST_NAME"='Dina')
5 - access("S"."CUST_ID"="C"."CUST_ID")
使⽤用customers當做driving table
Cost由
1838K降為54544
Time由06:07:47
降為00:10:55
5
1
2
3
4
Join Order
(CUSTOMERS為driving table)
不使⽤用CUST_FNAME_IDX

76. 同時變更Data Access
Method與Join Order
----------------------------------------------------------------------------------------------
| Id | Operation |Name | Rows| Bytes| Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 93 (100)| |
| 1 | SORT AGGREGATE | | 1| 17 | | |
| 2 | NESTED LOOPS | | 5557| 94469| 93 (0)|00:00:02 |
| 3 | TABLE ACCESS BY INDEX ROWID| CUSTOMERS | 43| 516 | 7 (0)|00:00:01 |
|* 4 | INDEX RANGE SCAN |CUSTOMERS_FNAME_IDX| 43| | 1 (0)|00:00:01 |
|* 5 | INDEX RANGE SCAN |SALES_CUSTID_IDX | 130| 650| 2 (0)|00:00:01 |
----------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("C"."CUST_FIRST_NAME"='Dina')
5 - access("S"."CUST_ID"="C"."CUST_ID")
SELECT COUNT(*)
FROM frank.sales s,frank.customers c
WHERE s.cust_id=c.cust_id AND c.cust_first_name=‘Dina’
3 5
2
1
4
Cost由1838K
減為93
Time由06:07:47
減為00:00:02
Join Order
(CUSTOMERS為driving table)

77. ----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 547 (100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
|* 2 | HASH JOIN | | 5557 | 94469 | 547 (1)| 00:00:07 |
| 3 | TABLE ACCESS BY INDEX ROWID|CUSTOMERS | 43 | 516 | 7 (1)| 00:00:01 |
|* 4 | INDEX FULL SCAN |CUST_FNAME_IDX | 43 | | 1 (1)| 00:00:01 |
| 5 | INDEX FULL SCAN |SALES_CUSTID_IDX| 918K| 4486K| 1958 (1)| 00:00:07 |
----------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("S"."CUST_ID"="C"."CUST_ID")
4 - access("C"."CUST_FIRST_NAME"='Dina')
變更Join Method-hash join
由Nested Loop
改為Hash Join
Cost由93增
加到547
Time由00:00:02
增加到00:00:07
5
1
2
3
4

78. 變更Join Method-sort merge
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes| Cost (%CPU)|Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 1966 (100)| |
| 1 | SORT AGGREGATE | | 1 | 17 | | |
| 2 | MERGE JOIN | | 5557 | 94469| 1966 (1)|00:00:24 |
| 3 | INDEX FULL SCAN |SALES_CUSTID_IDX| 918K| 4486K| 1958 (1)|00:00:24 |
|* 4 | SORT JOIN | | 43 | 516 | 8 (13)|00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| CUSTOMERS | 43 | 516 | 7 (1)|00:00:01 |
|* 6 | INDEX FULL SCAN | CUST_FNAME_IDX |55500 | | 1 (1)|00:00:01 |
----------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("S"."CUST_ID"="C"."CUST_ID")
filter("S"."CUST_ID"="C"."CUST_ID")
6 - access("C"."CUST_FIRST_NAME"='Dina')
改為Sort Merge Join
Cost由93增加
到1966
Time由00:00:02
增加到00:00:24
4
1
2
3
5
6

79. 使⽤用Index的建議
• 是否需要建⽴立
• 建⽴立在哪些欄位
• 單⼀一欄位或複合欄位
• 建⽴立何種形態
• B-Tree
• Bitmap
• Unique
• Non-Unique

80. What is INDEX
• An index is an optional structure,
associated with a table or table cluster,
that can sometimes speed data access. By
creating an index on one or more columns of
a table, you gain the ability in some cases
to retrieve a small set of randomly
distributed rows from the table. Indexes
are one of many means of reducing disk I/O.
Oracle® Database Concepts 11g Release 2 (11.2)
-3 Indexes and Index-Organized Tables

81. • Index or Not Index
• Index Cost
• Low Selectivity(BTree Index)
• Which columns
• FROM/WHERE clause
• Single/Multiple Column
• What Type
• BTree
• BitMap
• Uniqueness
• Non-Unique
• Unique

82. 其他Data Access Method
• Partitioned Table
• Cluster Table
• Index Cluster
• Hash Cluster
• Single Hash Cluster
• Index Organized Table
• Materialized view
• Materialized view log

83. Q&A