Do You Know The 11g Plan?

Do you know the 11g Plan?

Mahesh Vallampati

About the Speaker• Mahesh Vallampati

– Senior Practice Manager at SmartDog Services– Senior Sales Consulting Manager at Hotsos.– Director of IT Database Services at a company in

Houston– Worked at Oracle for nine years – Published in Oracle magazine

Agenda

• Plan Table• V$SQL_PLAN and Related Views• DBMS_XPLAN• Key Performance Takeaways

The Plan Table

Plan Table

• When Oracle parses a query, it creates a plan to execute the query

• The plan is a set of row source operations

• Row source operations are specific data access and join/sort method’s Oracle is going to execute to fulfill the request done by the query

• Some of the row source operations are– Index Scan’s (Unique, Range, Skip etc.)

– Table Access (By Index Rowid, Full Table Scan’s)

– Joins (Nested Loops, Hash, Sort-Merge)

– Sort Operations

Explain Plan Example - Iselect empno, ename, sal, deptno from emp where empno = 7654 ;

-----------------------------------------------------------------------------------

|Id | Operation | Name |Rows|Bytes|Cost (%CPU)|Time |

-----------------------------------------------------------------------------------

| 0| SELECT STATEMENT | | 1| 17| 1 (0)|00:00:01 |

| 1| TABLE ACCESS BY INDEX ROWID| EMP | 1| 17| 1 (0)|00:00:01 |

|* 2| INDEX UNIQUE SCAN | EMP_EMPNO_PK | 1| | 0 (0)|00:00:01 |

-----------------------------------------------------------------------------------

Predicate Information (identified by operation id):

---------------------------------------------------

2 - access("EMPNO"=7654)

Explain Plan Example - II

select ename from emp where comm is not null;

--------------------------------------------------------------------------

| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |

--------------------------------------------------------------------------

| 0 | SELECT STATEMENT | | 4 | 32 | 4 (0)| 00:00:01 |

|* 1 | TABLE ACCESS FULL| EMP | 4 | 32 | 4 (0)| 00:00:01 |

--------------------------------------------------------------------------


---------------------------------------------------

1 - filter("COMM" IS NOT NULL)

How to read an indented, ordered Oracle execution plan…• An execution plan line represents a row source

operation (RSO)• An indented RSO is the child of the first prior

less-indented RSO• A child RSO must complete before its parent can• Order of execution– RSOs begin in top-down order at step 0– RSOs complete only after their children complete

Plan Table

• The typical name for a plan table is PLAN_TABLE, but you may use any name you wish

• Create the plan table by running utlxplan.sql, located in $ORACLE_HOME/rdbms/admin– Create one per instance or one per schema

Explain Plan Examples

select empno, ename, sal, deptno from emp where empno = 7654 ;

-----------------------------------------------------------------------------------

|Id | Operation | Name |Rows|Bytes|Cost (%CPU)|Time |

-----------------------------------------------------------------------------------

| 0| SELECT STATEMENT | | 1| 17| 1 (0)|00:00:01 |

| 1| TABLE ACCESS BY INDEX ROWID| EMP | 1| 17| 1 (0)|00:00:01 |

|* 2| INDEX UNIQUE SCAN | EMP_EMPNO_PK | 1| | 0 (0)|00:00:01 |

-----------------------------------------------------------------------------------


---------------------------------------------------

2 - access("EMPNO"=7654)

Divide and Conquer for Bigger Plansselect d.dname, e.ename, s.grade, e.sal from dept d, emp e, salgrade s

where d.deptno = e.deptno and e.sal between s.losal and s.hisal ;

--------------------------------------------------------------------------------------

| Id | PID | Operation | Name | Rows | Bytes | Cost |

--------------------------------------------------------------------------------------

| 0 | | SELECT STATEMENT | | 1 | 28 | 7 |

| 1 | 0 | NESTED LOOPS | | 1 | 28 | 7 |

| 2 | 1 | MERGE JOIN | | 1 | 17 | 6 |

| 3 | 2 | SORT JOIN | | 13 | 117 | 2 |

|* 4 | 3 | TABLE ACCESS BY INDEX ROWID| EMP | 13 | 117 | 2 |

| 5 | 4 | INDEX FULL SCAN | EMP_SAL | 14 | | 1 |

|* 6 | 2 | FILTER | | | | |

|* 7 | 6 | SORT JOIN | | | | |

| 8 | 7 | TABLE ACCESS FULL | SALGRADE | 5 | 40 | 2 |

| 9 | 1 | TABLE ACCESS BY INDEX ROWID | DEPT | 1 | 11 | 1 |

|* 10 | 9 | INDEX UNIQUE SCAN | DEPT_DEPTNO_PK | 1 | | |

--------------------------------------------------------------------------------------


---------------------------------------------------

4 - filter("E"."DEPTNO" IS NOT NULL)

6 - filter("E"."SAL"<="S"."HISAL")

7 - access("E"."SAL">="S"."LOSAL")

filter("E"."SAL">="S"."LOSAL")

10 - access("D"."DEPTNO"="E"."DEPTNO")

Plan Table Evolution• The Plan Table Contains the information about the forecasted row source operations

for the execution of the SQL statements• The changes in the PLAN_TABLE across versions.• Introduced in 9i

– Access Predicates– Filter Predicates

• 9i to 10.1– Projection– Time– QBlock_name– Plan_id– Object_Alias– Depth

• 10.1 to 10.2– other_xml

• 10.2 to 11g– No Changes

DBMS_XPLAN

DBMS_XPLAN

• Introduced in 9iR2• Easy way of viewing the output of the EXPLAIN

PLAN command in several, predefined formats • 10g has some enhanced functionality• We will use the DISPLAY function of

DBMS_XPLAN available in 9iR2, 10g and 11g

DBMS_XPLAN

• Ensure that you are using the right version of the– PLAN_TABLE– DBMS_XPLAN

• Version incompatibilities may cause some issues

• Where is plan table and DBMS_XPLAN? – Plan Table -

$ORACLE_HOME/rdbms/admin/utlxplan.sql– DBMS_XPLAN -

$ORACLE_HOME/rdbms/admin/dbmsxpln.sql

Using DBMS_XPLAN

EXPLAIN PLANSET STATEMENT_ID = 'abc' FORselect object_type, count(1) from dba_objectswhere owner= 'SCOTT'group by object_type;

DBMS_XPLAN.DISPLAY Options

Format parameter for this function choices are• BASIC – Just displays the minimum information

in the plan• TYPICAL – Displays the relevant information in

the plan and predicate information (PX information if applicable)

• SERIAL – Like typical, but no parallel execution information even if applicable

• ALL – All of typical including projections, alias, etc.

DBMS_XPLAN. DISPLAY Examples

SELECT * FROM TABLE(dbms_xplan.display('PLAN_TABLE', 'abc','BASIC'));

SELECT * FROM TABLE(dbms_xplan.display('PLAN_TABLE', ‘abc','TYPICAL'));

SELECT * FROM TABLE(dbms_xplan.display('PLAN_TABLE',

'abc','ALL'));

These are display formats for DBMS_XPLAN

DBMS_XPLAN.DISPLAY Output

DBMS_XPLAN Package - # of Procedures and Functions

0

2

4

6

8

10

12

14

9i 10g 11g

Recap

• DBMS_XPLAN has been around since 9.2• It is an elegant way of looking at EXPLAIN PLAN

outputs• The “TYPICAL” option of

DBMS_XPLAN.DISPLAY is most useful because it ties predicate information (access and filters) back to the predicted row source operation lines in the explained plan

• 11g introduced XML as an output option for plans

V$ SQL_PLAN Views

V$SQL and Related views

View Name Description

V$SQL The SQL Statement that is being executed and its non-plan details

V$SQL_PLAN Contains the execution plan information for each child cursorloaded in the library cache

V$SQL_PLAN_STATISTICS* Provides execution statistics at therow source level for each childcursor

V$SQL_PLAN_STATISTICS_ALL*(Merges V$SQL_PLAN_STATISTICS with V$SQL_AREA)

Contains memory usage statisticsfor row sources that use SQLmemory (sort or hash-join)

V$SQL – New Columns in 11g

ColumnData Type Comment

TYPECHECK_MEM NUMBER ???IS_BIND_SENSITIVE VARCHAR2(1) Indicates whether the cursor is bind sensitive

(Y) or not (N). A query is considered bind-sensitive if the optimizer peeked at one of its bind variable values when computing predicate selectivities and where a change in a bind variable value may cause the optimizer to generate a different plan.

IS_BIND_AWARE VARCHAR2(1) Indicates whether the cursor is bind aware (Y) or not (N). A query is considered bind-aware if it has been marked to use extended cursor sharing. The query would already have been marked as bind-sensitive.

IS_SHAREABLE VARCHAR2(1) Indicates whether the cursor can be shared (Y) or not (N)

SQL_PATCH VARCHAR2(30) SQL patch used for this statement, if any

SQL_PLAN_BASELINE VARCHAR2(30) SQL plan baseline used for this statement, if any

V$SQL and Related views in 11g

View Name 11g enhancement

V$SQL_PLAN Added child address and timestamp column

V$SQL_PLAN_STATISTICS* Added child address column

V$SQL_PLAN_STATISTICS_ALL*(Merges V$SQL_PLAN_STATISTICS with V$SQL_AREA)

Added child address column

Viewing V$SQL_PLAN Data

• DBMS_XPLAN has made it easier to look at the data underlying the V$SQL_PLAN and V$SQL_PLAN_STATISTICS data

• Available starting 10g• Lets you view the run time plan or the execution

plan of a SQL Statement• Also, lets you view the execution statistics for a

run of the SQL Statement or all prior runs

Key Performance Takeaways

New in 11g

SQL Plan Baselines

SQL Plan BaselinesDBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE takes in three

arguments.

• SQL_HANDLE SQL_HANDLE from dba_sql_plan_baselines

• PLAN_NAME Name of the plan

• FORMAT BASIC, TYPICAL, ALL

Init.ora paramter optimizer_capture_sql_plan_baselines = true•

FUNCTION DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE RETURNS DBMS_XPLAN_TYPE_TABLE

Argument Name Type In/Out Default?

------------------------------ ----------------------- ------ --------

SQL_HANDLE VARCHAR2 IN DEFAULT

PLAN_NAME VARCHAR2 IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

SQL Plan Baselinesselect * from

table(dbms_xplan.display_sql_plan_baseline('SYS_SQL_8bab62f0bc1db3bc'))

PLAN_TABLE_OUTPUT

----------------------------------------------------------------

SQL handle: SYS_SQL_8bab62f0bc1db3bc

SQL text: select /*+ full(t1) */ * from t1 where c1 = 1

----------------------------------------------------------------

SQL Plan BaselinesPlan name: SYS_SQL_PLAN_bc1db3bc750635c2

Enabled: YES Fixed: NO Accepted: YES Origin: MANUAL-LOAD

-------------------------------------------------------------------------------------

Plan hash value: 1420382924

-------------------------------------------------------------------------------------


-------------------------------------------------------------------------------------


| 1 | TABLE ACCESS BY INDEX ROWID| T1 | 1 | 9 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | T1_N1 | 1 | | 1 (0)| 00:00:01 |

-------------------------------------------------------------------------------------


2 - access("C1"=1)

SQL Plan BaselinesPlan name: SYS_SQL_PLAN_bc1db3bcdbd90e8e

Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE

--------------------------------------------------------------------------


--------------------------------------------------------------------------


--------------------------------------------------------------------------


|* 1 | TABLE ACCESS FULL| T1 | 1 | 9 | 59 (6)| 00:00:01 |

--------------------------------------------------------------------------


---------------------------------------------------

1 - filter("C1"=1)

Plan Output in XML Format

DBMS_XPLAN.BUILD_PLAN_XML

dbms_xplan.build_plan_xml(

table_name IN VARCHAR2 DEFAULT 'PLAN_TABLE',

statement_id IN VARCHAR2 DEFAULT NULL,

plan_id IN NUMBER DEFAULT NULL,

format IN VARCHAR2 DEFAULT 'TYPICAL',

filter_preds IN VARCHAR2 DEFAULT NULL,

plan_tag IN VARCHAR2 DEFAULT 'plan',

report_ref IN VARCHAR2 DEFAULT NULL)

Example Output

EXPLAIN PLAN

SET STATEMENT_ID = 'abc'

FOR

select object_type, count(1)

from dba_objects

where owner= 'SCOTT'

group by object_type;

The SQL Statement

SELECT dbms_xplan.build_plan_xml(statement_id => 'abc') AS XPLAN FROM dual;

accomplishes this.

Still the good stuff…

Access Predicates / Filter Predicates

Access and Filter Predicatesselect attribute1

from bom

where item_id=11

and org_id=2

and designator is null;

The Explain plan shows

--------------------------------------------------------------------------------------


--------------------------------------------------------------------------------------


|* 1 | TABLE ACCESS BY INDEX ROWID| BOM | 196 | 10584 | 142 (1)| 00:00:02 |

|* 2 | INDEX RANGE SCAN | BOM_N1 | 11961 | | 31 (0)| 00:00:01 |

--------------------------------------------------------------------------------------


---------------------------------------------------

1 - filter("DESIGNATOR" IS NULL)

2 - access("ITEM_ID"=11 AND "ORG_ID"=2)

The Stat Lines Show

STAT #4 id=1 cnt=4889 pid=0 pos=1 obj=70702 op='TABLE ACCESS BY INDEX ROWID BOM (cr=787 pr=150 pw=0 time=194697 us)'

STAT #4 id=2 cnt=11961 pid=1 pos=1 obj=70704 op='INDEX RANGE SCAN BOM_N1 (cr=357 pr=37 pw=0 time=91948 us)'

Access and Filter Predicatesselect attribute1

from bom where

item_id=11

and org_id=2

and designator is null

--------------------------------------------------------------------------------------


--------------------------------------------------------------------------------------


| 1 | TABLE ACCESS BY INDEX ROWID| BOM | 196 | 10584 | 4 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | BOM_U1 | 1 | | 3 (0)| 00:00:01 |

--------------------------------------------------------------------------------------


---------------------------------------------------

2 - access("ITEM_ID"=11 AND "ORG_ID"=2 AND "DESIGNATOR" IS NULL)

STAT Lines

STAT #12 id=1 cnt=4889 pid=0 pos=1 obj=70702 op='TABLE ACCESS BY INDEX ROWID BOM (cr=713 pr=0 pw=0 time=50184 us)'

STAT #12 id=2 cnt=4889 pid=1 pos=1 obj=72016 op='INDEX RANGE SCAN BOM_U1 (cr=339 pr=0 pw=0 time=19590 us)'

Takeaway

• Look for row source operation that are filtering a lot of rows

• When a row source operation is filtering a lot of rows, it is accessing those rows and then applying the filter to discard rows that do not match the predicate qualifier

• Evaluate indexes to access the data and not filter it

Query Blocks

Query Blocks• Useful when trouble shooting

– Nested SQL Statements– Complex SQL Statements– Inline Views– Sub-Queries– Repeated Visits to Table

• 10g allows you to name Query Blocks– QB_NAME Hint

• e.g. /*+ QB_NAME(dept_subquery) */

– When people write complex SQL statements, require them to name Query Blocks

• Query Blocks– Add clarity to execution and explain plans

ExampleSELECT /*+ QB_NAME(outer) */ e.ename , e.sal FROM ( SELECT /*+ QB_NAME(inline_view) */ * FROM emp e WHERE e.sal > 300 AND e.deptno IN ( SELECT /*+ QB_NAME(dept_subquery) */

d.deptno FROM dept d WHERE d.dname IN ('SALES','ACCOUNTING')

) ) e;

Query Block with DBMS_XPLAN

SQL> SELECT plan_table_output

2 FROM TABLE(DBMS_XPLAN.DISPLAY('PLAN_TABLE','qb_name','ALL'));

PLAN_TABLE_OUTPUT

-----------------------------------------------------------------------------------------


----------------------------------------------------------------------------------------


----------------------------------------------------------------------------------------


| 1 | MERGE JOIN | | 7 | 182 | 6 (17)| 00:00:01 |

|* 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 2 | 26 | 2 (0)| 00:00:01 |

| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |

|* 4 | SORT JOIN | | 14 | 182 | 4 (25)| 00:00:01 |

|* 5 | TABLE ACCESS FULL | EMP | 14 | 182 | 3 (0)| 00:00:01 |

----------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):

-------------------------------------------------------------

1 - SEL$B9DAFA34

2 - SEL$B9DAFA34 / D@DEPT_SUBQUERY

3 - SEL$B9DAFA34 / D@DEPT_SUBQUERY

5 - SEL$B9DAFA34 / E@INLINE_VIEW

DBMS_XPLAN.DISPLAY_AWR

DBMS_XPLAN.DISPLAY_AWR

DBMS_XPLAN.DISPLAY_AWR takes in four arguments.

• SQL_ID The SQL_ID of the statement in AWR

• PLAN_HASH_VALUE The Plan Hash value if available

• DB_ID The Database Id

• FORMAT Format Options.

Need Data From…

• dba_hist_sql_plan• dba_hist_sqltext• v_$database

SELECT * FROM TABLE

(dbms_xplan.display_awr('24033vh7b098h'));

DBMS_XPLAN.DISPLAY_SQLSET


FUNCTION DISPLAY_SQLSET RETURNS DBMS_XPLAN_TYPE_TABLE


------------------------------ ----------------------- ------ --------

SQLSET_NAME VARCHAR2 IN

SQL_ID VARCHAR2 IN

PLAN_HASH_VALUE NUMBER(38) IN DEFAULT


SQLSET_OWNER VARCHAR2 IN DEFAULT

Need to license

Diagnostic Pack

Tuning Pack


For example, a SQL Tuning set named ‘MY_TUNING_SET’ for the sql statement with the sql_id 'g1pz63cqh5qbf', the following will displays all the execution plans.

An example:

SELECT * FROM table (DBMS_XPLAN.DISPLAY_SQLSET('MY_TUNING_SET,'g1pz63cqh5qbf'));

DBMS_XPLAN.DISPLAY_CURSOR

DBMS_XPLAN.DISPLAY_CURSOR

FUNCTION DISPLAY_CURSOR RETURNS DBMS_XPLAN_TYPE_TABLE


----------------- ------------- ------ --------

SQL_ID VARCHAR2 IN DEFAULT

CURSOR_CHILD_NO NUMBER(38) IN DEFAULT


SQL_ID SQL_ID From V$SQL

CURSOR_CHILD_NO CHILD_NUMBER in V$SQL

Obtaining SQL_ID and Cursor Child Num.SELECT sql_id, child_number, sql_textFROM v$sqlWHERE LOWER(sql_text) LIKE ‘<begin sql statement string>%'

FORMAT

• BASIC, TYPICAL, SERIAL, ALL– To view the execution plans alone

• Viewing Stats about the plan– Introduced in 10g R1– Enhanced in 10g R2– Set STATISTICS_LEVEL=ALL at the session level

• OR

– Set the GATHER_PLAN_STATISTICS hint

Viewing the execution plan in V$SQL

SELECT plan_table_outputFROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR('3a3dz5yva4vnf',0,'ALL'));

Viewing the Run Time Stats of the Execution PlanSELECT plan_table_output

FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR('3a3dz5yva4vnf',0,‘<Various Options>'));

• IOSTATS

• MEMSTATS

• ALLSTATS

• IOSTATS LAST

• MEMSTATS LAST

• ALLSTATS LAST

Demo

• Demo.sql

Q&Q U E S T I O N SQ U E S T I O N SA N S W E R SA N S W E R S

Do You Know The 11g Plan?

Technology

plan table evolution

plan table isplan

table access

table dbms

g plan

plan command

plan examples

agenda plan table v