Sql performance vesl technologies

Performance Tuning
SQL and PL/SQL
Presentation By
P. S. Mukesh Yadav and Suresh C Mishra

11/10/2008

VESL TECHNOLOGIES LTD

1

• Tips in SQL
• Tips in PL/SQL

11/10/2008

Topics


2

Tips in SQL
• Limit the use of sub queries; often they can
be replaced with a JOIN.
• Use EXISTS and more specific conditions in
the where clause instead of the DISTINCT
clause to eliminate duplicates.
• Never Mix Datatypes.Use character and
number appropriately according to the
usage.
11/10/2008


3

Example of First Tip…
SELECT ename FROM emp
WHERE deptno IN
(SELECT deptno FROM emp
WHERE comm = 10
AND sal>4000);

SELECT ename FROM emp d
WHERE EXISTS (
SELECT e.deptno FROM emp e
WHERE 1=1
and e.deptno = d.deptno
AND e.comm = 10
AND e.sal > 4000);

SELECT ename FROM emp e,dept d
WHERE e.deptno = d.deptno
AND e.comm = 10
AND e.sal > 4000

11/10/2008


4

Example of Second Tip…
Ex :

SELECT
ooha.order_type_id,ooha.order_
number
FROM oe_order_headers_all
ooha
WHERE EXISTS (SELECT 1
FROM oe_transaction_types_tl
ottt
WHERE ooha.order_type_id =
ottt.transaction_type_id);

select distinct
ooha.order_type_id,ooha.
order_number
from
oe_order_headers_all
ooha,oe_transaction_type
s_tl ottt
where
ooha.order_type_id =
ottt.transaction_type_id

11/10/2008


5

Tips in SQL Contd..
• Avoid the use of NOT IN.Instead, a NOT
EXISTS sub query may run faster.
• Use Minus Operator instead of Exists sub
queries(Not in and Not Exists) results in
faster execution plan.
• Rewrite (negative(ex : not in)) sub queries as
outer joins to improve performance.
• Never use numbers in sorting.
11/10/2008


6

Contd….
Ex :
SELECT * FROM EMP A WHERE DEPTNO NOT
IN (SELECT DEPTNO FROM DEPT WHERE
DEPTNO=A.DEPTNO)

select * from
ap_invoices_all where invoice_id not in(select
invoice_id from
ap_invoice_payments_all
)

11/10/2008

SELECT * FROM EMP A WHERE NOT EXISTS
(SELECT 1 FROM DEPT WHERE
DEPTNO=A.DEPTNO)

SELECT aia.invoice_id
FROM ap_invoices_all aia,
ap_invoice_payments_all aipa
WHERE aia.invoice_id = aipa.invoice_id(+);


7

Contd….
Ex :

select * from
ap_invoices_all where
invoice_id not in(select
invoice_id from
)

SELECT * FROM
ap_invoices_all aia WHERE NOT
EXISTS (SELECT * FROM
ap_invoice_payments_all WHERE
invoice_id = aia.invoice_id)

select * from
ap_invoices_all
where invoice_id in
(select invoice_id from
ap_invoices_all
minus
select invoice_id from
)

11/10/2008


8

Tips in SQL Contd..

• Avoid running a query in a loop.Make use of
UNION and execute it at the end of the loop.
• Avoid the LIKE predicate.Always replace
LIKE with = when appropriate.
• Use LIKE rather than the SUBSTR function.
• Avoid Where Column Like '%string'.
• Consider Indexes for Max() and Min().

11/10/2008


9

Contd….
• Ex :

select * from
dept where dname like
'RESEARCH'

select ename from emp
where ename like ‘X%’

11/10/2008

select * from
dept where dname =
'RESEARCH'

select ename from emp
where
substr(ename,1,1) = ‘X’


10

Tips in SQL Contd..
• Use Decode and Case for complex
aggregations.
• Use WHERE instead of HAVING.
• Use UNION ALL instead of UNION.
• Prefer using GROUP BY only when any
aggregate functions are present.
• Avoid usage of ‘TO_CHAR‘ and use ‘TRUNC‘
instead.
11/10/2008


11

Contd….
• Ex :

SELECT E_Name FROM
Employees_Norway UNION SELECT
E_Name FROM Employees_USA

select *
from emp
where to_char(emp_joindate,
’mmddyyyy’) < to_char(sysdat
e,’mmddyyyy’)

11/10/2008

Ex :
SELECT E_Name FROM
Employees_Norway UNION ALL
SELECT E_Name FROM
Employees_USA

select *
from emp
where emp_joindate < trunc
(sysdate)


12

SELECT COUNT(*)
FROM emp
WHERE status = 'Y'
AND emp_name LIKE
'SMITH%';

SELECT COUNT(*)
FROM emp
WHERE status = 'N'
AND emp_name LIKE
'SMITH%';

Ex :
SELECT DEPTID,
SUM(SALARY)
FROM EMP
GROUP BY DEPTID
HAVING DEPTID = 100;

SELECT COUNT(DECODE(status, 'Y', 'X', NULL))
Y_count,
COUNT(DECODE(status, 'N', 'X', NULL))
N_count
FROM emp
WHERE emp_name LIKE 'SMITH%';

11/10/2008

SELECT DEPTID,
SUM(SALARY)
FROM EMP
WHERE DEPTID = 100
GROUP BY DEPTID;


13

Contd….
SELECT COUNT (*)
FROM emp
WHERE sal < 2000;

SELECT COUNT (*)
FROM emp
WHERE sal BETWEEN 2000
AND 4000;

SELECT COUNT (*)
FROM emp
WHERE sal>4000;

SELECT COUNT (CASE WHEN sal < 2000
THEN 1 ELSE null END) count1,
COUNT (CASE WHEN sal BETWEEN 2001 AND 4000
THEN 1 ELSE null END) count2,
COUNT (CASE WHEN sal > 4000
THEN 1 ELSE null END) count3
FROM emp;

11/10/2008


14

Tips in SQL Contd..
• Use NVL to check against a number instead
of the NULL value.
• Use <= 99 and >= 1 instead of < 100 and > 0
for faster comparisons.
• Avoid using functions on indexed columns.
• Use SET TIMING ON to test the execution
time of a slow query.
• Use EXPLAIN PLAN to view the execution
steps of a slow query.
11/10/2008


15

Contd….
• Ex :
select cdl.* from
cs_incidents_all_b ciab,
jtf_tasks_b jtb,
jtf_task_assignments jta,
csf_debrief_headers cdh,
csf_debrief_lines cdl
where ciab.incident_id = jtb.source_object_id
and jtb.task_id = jta.task_id
and jta.task_assignment_id = cdh.task_assignment_id
and cdh.debrief_header_id = cdl.debrief_header_id
and ciab.incident_number = '1097852'

11/10/2008


16

Contd….
Operation
SELECT STATEMENT Optimizer Mode=CHOOSE
TABLE ACCESS BY INDEX ROWID
NESTED LOOPS
NESTED LOOPS
NESTED LOOPS
NESTED LOOPS
INDEX UNIQUE SCAN
TABLE ACCESS FULL
INDEX RANGE SCAN
INDEX RANGE SCAN
INDEX RANGE SCAN

11/10/2008

Object Name

CSF_DEBRIEF_LINES

CS_INCIDENTS_ALL_B
CS_INCIDENTS_U2
JTF_TASKS_B
JTF_TASK_ASSIGNMENTS
JTF_TASK_ASSIGNMENTS_N2
CSF_DEBRIEF_HEADERS
CSF_DEBRIEF_HEADERS_N1
CSF_DEBRIEF_LINES_N1

Rows Bytes
4
3
4
1
1
1
1
1
1
1
2
1
1
4

Cost Object Node In/Out

PStart

PStop

1134
3
1134
1131
1129
1126
4
2
10 1122
20
3
2
14
2
1
2

414
776
56
42
22
12


17

Contd….
Ex :

select sys.resourceID,
sys.client_version0
from dbo.v_R_System as sys
where UPPER(netbios_name0) =
'COMPUTER'

select sys.resourceID,
sys.client_version0
from dbo.v_R_System as sys
where netbios_name0 =
'COMPUTER’

11/10/2008


18

Tips in SQL Contd..
• Remove unnecessary large full table scans.
• Minimize outer joins and use them only if
necessary.
• Only use CHAR for data that must be an exact
length such as phone numbers or gender
identification fields because it pads variable
length data with white-space that will cause
string comparisons to fail.

11/10/2008


19

Tips in SQL Contd..
• Use an indexed column or primary key
column when counting rows.
• Avoid unnecessary sorting.
• Always better to use base tables instead of
views.
• If a view is in a query,try to optimize the view
first before optimizing the query.
• Always place all the hard-coded values at the
end of a query.
11/10/2008


20

Contd….
• Ex :
select count(*)
From emp

11/10/2008

select
count(emp _id) from
emp;


21

Tips in SQL Contd..
•
•
•
•
•

Using the indexes carefully.
Position of Tables in the proper order.
Sequence of Joins in the Where Clause.
Put the queries as simple as possible.
Avoid using of NOT when ever dealing with
Indexed Columns.
• Avoid usage of ! Operator use > instead.
• Always use a column list in your INSERT
statements.
11/10/2008


22

Contd….
Ex :
select *
from emp
where emp_id !=
007

INSERT INTO
EuropeanCountries
VALUES (1, 'Ireland')

11/10/2008

select *
from emp
where emp_id > 0

INSERT INTO
EuropeanCountries
(CountryID,
CountryName)
VALUES (1, 'England')


23

Tips in SQL Contd..

• Make Use of rownum.
• To Check Duplicate Data in a Query.

• Use SQL standards and conventions to
reduce parsing.
• Make sure to do INSERT,UPDATE and DELETE
operations prior checking the data with a
SELECT statement with proper conditions in
the where clause.
• Recheck whether any joins are missing.
11/10/2008


24

Ex :

Contd….
SELECT DOCUMENT_NO,COUNT(*)
FROM documents
GROUP BY DOCUMENT_NO
HAVING
COUNT(*) > 1;

11/10/2008


25

Tips in SQL Contd..

• Use Column Names instead of * in a SELECT
Statement.
• Use an index on the most queried columns in
SELECT, WHERE, and JOIN statements.
• Use BETWEEN instead of IN.
• Make sure all joined tables have a matching
join condition.
• Make sure columns selected from multiple
tables are dereferenced by an alias.
11/10/2008


26

Contd….
• Ex :
SELECT empno FROM emp WHERE
empno IN (508858, 508859,
508860, 508861,508862, 508863,
508864)

11/10/2008

SELECT empno FROM emp WHERE
empno BETWEEN 508858 and
508864


27

Tips in SQL Contd..
•
•
•
•
•

Call Functions in SQL Queries.
Minimize Table Lookups in a Query.
Use where instead of Order By.
Never do a calculation on an indexed column.
Give the names from _tl tables instead of
hard-coding the id.Ex : Status
• Add Who Columns for any new table created
for easier archiving.

11/10/2008


28

Contd….
Ex :
select tab_name from tables where
tab_name = (select tab_name from
tab_columns where version = 604) and
db_ver = (select db_ver from
tab_columns where version = 604)

update emp set emp_cat = (select
max(category) from
emp_categories),sal = (select
max(salrange) from
emp_categories)where emp_dept =
20

11/10/2008

select tab_name from tables where
(tab_name, db_ver) = (select
tab_name,db_ver from tab_columns
where version = 604)

update emp set (emp_cat , sal )=
(select max(category),
max(salrange) from
emp_categories) Where
emp_dept = 20


29

Contd….
Ex :
select * from emp
where
sal*12>25000

11/10/2008

select * from emp
where
sal>25000/12


30

Tips in SQL Contd..
• Use sub queries and joins instead of multiple
separate queries.
• Use >= instead of >
• Use Union in place of OR for Indexed
Columns.
• Use the EXISTS clause or = operator instead
of the IN clause whenever you need a single
record.

11/10/2008


31

Contd….
Ex :
select * from
where order_number>3

11/10/2008

select * from
where order_number>=4


32

Tips in SQL Contd..
• Avoid IS NULL & IS NOT NULL on Indexed
Columns.Use >=0 if necessary.
• Use a system generated ID as the primary
key to avoid duplicates.
• Use Optimizer Hints.
• Generate a tkprof and observe the trace file.
• Focus on critical transactions(Production
Data)..

11/10/2008


33

Contd….
Ex :

11/10/2008

/*+index(t1) index(t2)……..index(tn)*/
/*+FULL(t1) FULL(t2)……FULL(tn)*/
/*+OPTIMIZER_GOAL=CHOOSE*/
/*+OPTIMIZER_GOAL=FIRST_ROWS*/
/*+ORDERED*/
/*+RULE*/
/*+OPTIMIZER_GOAL=ALL_ROWS*/
/*+OPTIMIZER_GOAL=ORDERED*/
/*+OPTIMIZER_GOAL=RULE*/
/*+USE_NL(t1,t2,t3,t4,t5,t6) ORDERED */


34

Tips in PL/SQL
•
•
•
•

Break the piece of code into small blocks to
achieve modularity.
Grouping related logic as a single block.
Use Packages for each major functionality.
Avoid hard-coding.

11/10/2008


35

Tips in PL/SQL Contd..

• Follow PL/SQL Coding standards for
procedures, variables, table types,rec types,
functions and packages.
• Encapsulate your SQL.
• Avoid repeating the SQL in different places.
• Exception Handling.
• Usage of Bind Variables and Global Variables.
• Make Function Calls efficiently.

11/10/2008


36

• Use BULK COLLECT when there is huge
amount of data to be fetched from a select
query in a cursor.
• Use FOR ALL.
• Use Bulk Bind.
• Reorder Conditional Tests to put the Least
Expensive First.
• Logic in a simplest way.
• Usage of End Labels.
• Avoid usage of mutating tables.
11/10/2008


37

• Ex :

11/10/2008

Contd….

CREATE OR REPLACE FUNCTION get_a_mess_o_emps
(deptno_in IN dept.depno%TYPE)
RETURN emplist_t
IS
emplist emplist_t := emplist_t();
TYPE numTab IS TABLE OF NUMBER;
TYPE charTab IS TABLE OF VARCHAR2(12);
TYPE dateTab IS TABLE OF DATE;
enos numTab;
names charTab;
hdates dateTab;
BEGIN
SELECT empno, ename, hiredate
BULK COLLECT INTO enos, names, hdates
FROM emp
WHERE deptno = deptno_in;
emplist.EXTEND(enos.COUNT);
FOR i IN enos.FIRST..enos.LAST
LOOP
emplist(i) := emp_t(enos(i),
names(i), hiredates(i));
END LOOP;
RETURN emplist;
END;

38

Contd….
• Ex :
PROCEDURE reality_meets_dotcoms (deptlist dlist_t)
IS
BEGIN
FORALL aDept IN deptlist.FIRST..deptlist.LAST
DELETE emp WHERE deptno = deptlist(aDept);
END;

11/10/2008


39

• Use Anchored declaration during declaration of
variables.
• Reduce N/w traffic.
• Make use of ‘user_’ tables or views in the
custom packages.
• Use Standard Public Apis.
• Group related sub-programs in a Package.
• Make use of Optimizer Hints.

11/10/2008


40

• Make use of the apis being called in the
standard forms of Oracle Applications.
• Minimize Datatype Conversions.
• Use of CASE statements, is a much better
alternative to nested if-elsif statements.
• Declare Local Variables – Oracle Datatype.
• Make Loops as Efficient as Possible.

11/10/2008


41

• Use of pls_integer to declare integers and
binary_float or binary_double for floating
point.
• Replace and simplify IF statements with
Boolean expressions.
• Never exit from a FOR or WHILE loops.
• Never declare the FOR loop index (either an
integer or a record).
• Minimize the function Calls.
11/10/2008


42

Contd……
•
•
•
•

Unit Testing.
Debugging.
Analysis on the Exceptions.
Test Cases.

11/10/2008


43

Contd…

Thank You

11/10/2008


44

Sql performance vesl technologies

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie Sql performance vesl technologies

Ähnlich wie Sql performance vesl technologies (20)

Mehr von Suresh Mishra

Mehr von Suresh Mishra (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (8)

Sql performance vesl technologies