1 MyOnlineITCourses.com 1 MyOnlineITCourses.com Oracle Partitioning -- A Primer

1 MyOnlineITCourses.com1 MyOnlineITCourses.com1 MyOnlineITCourses.com

Oracle Partitioning -- A Primer


Partitioning

Partitioning is the ability of the database to take very large tables or indexes and

physically break them into

smaller

manageable pieces.


Partitioned VS Non Partitioned Table


Partitions - Benefits

Large Table

Difficult to Manage

Partition

Divide and Conquer

Easier to Manage

Improve Performance

Composite Partition

Better Performance

More flexibility to match business needs

JAN FEB

USA

EUROPE

ORDERS

Transparent to applications

ORDERS

JAN FEB

ORDERS


Partitioning - Benefits

Faster

• Queries will access only those relevant partitions

Cheaper

• An entire partition can be exported• Exported partition can be deleted from

database

Flexible

• Partition Maintenance is simpler when compared to a large un-partitioned table

• Partition backup/restoration is easier


When To Partition - Table

Here are some suggestions for when to partition a table:

Tables greater than 2 GB should always be considered as candidates for partitioning.

Tables containing historical data, in which new data is added into the newest partition.

A typical example is a historical table where only the current month's data is updatable and the other 11 months are read only.

When the contents of a table need to be distributed across different types of storage devices.


Partition Strategies

Range Hash List Composite


Partition Type .. (Examples)


Range Partitioned Tables

• Data distribution is based on range of values• Data distribution is continuous• Best performance when data distribution is

even on the partition key.• Knowledge of data is critical before choosing

this

Definition

• Date as partitioning key Jan 2011, Feb 2011, Mar 2011 so on..

• Department code as partitioning key Values <= 30, Values > 30

Example


DDL Example …

CREATE TABLE DEPT (

DEPTNO NUMBER (2),

DEPT_NAME VARCHAR2 (30))

PARTITION BY RANGE (DEPTNO)

(

PARTITION D1 VALUES LESS THAN (10) TABLESPACE DEPT1,

PARTITION D2 VALUES LESS THAN (20) TABLESPACE DEPT2,

PARTITION D1 VALUES LESS THAN (MAXVALUE) TABLESPACE DEPT3

)


Range Partition (Multi column)

• Defined on two or more columns of the table

Multi Column Range Partition

• Enhances Query performance if searched on partition key

• Improves the Manageability of partitions

Advantages


When to use Range Partition

Very large tables being scanned on a

range predicate like

Order-Date

Need to maintain rolling window of

data

Very less time for

administrative operations

like backup on large tables


Hash PartitioningP

art

itio

n K

ey

Specify the number of partitions

Alw

ays D

efi

ne

2n

Part

itio

ns

Oracle database inserts rows based on hash value of partition key

Sto

rag

e

Specify storage for the entire table and the tablespace for partitions


Hash Partition – Example

Hash-partitioned table that splits the table into four parts based on the hash of the partition key, acct_no.

CREATE TABLE CUST_SALES_HASH (

ACCT_NO NUMBER (5),

CUST_NAME CHAR (30))

PARTITION BY HASH (ACCT_NO) PARTITIONS 4

STORE IN (USERS1, USERS2, USERS3, USERS4);


When to use Hash Partition

Improve Manageability/availabilit

y of Large tables

Avoid data skew in partitions

Maximize I/0 throughput


List Partitioning

• Segmenting data with a list of values

• Flexible means of partitioning where data is better

understood

• Similar to Range Partitioning, but without any max

value

Definition

• CREATE TABLE DEPT_PART (DEPTNO NUMBER (2),DNAME VARCHAR2

(14),LOC VARCHAR2 (13))

PARTITION BY LIST (DNAME)

(PARTITION

D1_EAST VALUES (‘NEW YORK’),

PARTITION D2_WEST VALUES (‘SAN FRANCISCO’, ‘LOS ANGELES’),

PARTITION D3_SOUTH VALUES (‘ATLANTA’,’DALLAS’,’HOUSTON’),

PARTITION D4_NORTH VALUES (‘CHICAGO’,’DETROIT’));

Example


Range ,List , Hash Partitions


Composite Partitioning

Data is Partitioned along two

dimensions

A distinct value pair for

the two dimensions

uniquely determines the target partition

Composite Partitioning

is complementa

ry to multi column range

partition


Composite Partitioning Strategies

New 11g Strategy Use Case

List – Range Geography –Time

Range - Range Ship Date – Order Date

List - Hash Geography – OrderID

List - List Geography – Product


Range – List Partitioning


Composite PartitioningRange - Range

Jan 2006

... ...

Feb 2006 Mar 2006 Jan 2007

... ...

... ...

...

...

...

...

Jan 2006

Feb 2006

May 2006

Mar 2006

• All records with order_date in March 2006 ANDship_date in May 2006

May2006

ship_date

order_date

Table SALESRANGE(order_date)-RANGE(ship_date)


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1 MyOnlineITCourses.com 1 MyOnlineITCourses.com Oracle Partitioning -- A Primer