Oracle Partitioning - A Concise Guide to Partition Types and Strategies

Oracle Partitioning -- A Primer

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Partitioning

Partitioning is the ability of the database to take very
large tables or indexes and
 physically break them into
 smaller

 manageable pieces.

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Partitioned VS Non Partitioned Table

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Partitions - Benefits

ORDERS ORDERS ORDERS
USA

EUROPE
JAN FEB JAN FEB
Large Table Partition Composite Partition
Difficult to Manage Divide and Conquer Better Performance
Easier to Manage More flexibility to match
business needs
Improve Performance

Transparent to applications

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Partitioning - Benefits
• Queries will access only those relevant
partitions
Faster

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

• Partition Maintenance is simpler when
compared to a large un-partitioned table
Flexible • Partition backup/restoration is easier

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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.

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Partition Strategies

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Partition Type .. (Examples)

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Range Partitioned Tables

• Data distribution is based on range of values
• Data distribution is continuous
Definition • Best performance when data distribution is even on
the partition key.
• Knowledge of data is critical before choosing this

• Date as partitioning key
Jan 2011, Feb 2011, Mar 2011 so on..
Example
• Department code as partitioning key
Values <= 30, Values > 30

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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
)

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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
Advantages
partitions

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When to use Range Partition
Very less time
Very large for
tables being administrative
scanned on a operations like
range predicate backup on large
like Order-Date tables

Need to maintain
rolling window of
data

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Hash Partitioning

Specify the Oracle Specify

Always Define 2n Partitions
number of database storage for
Partition Key

partitions inserts the entire

Storage
rows table and
based on the
hash value tablespace
of partition for
key partitions

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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);

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When to use Hash Partition

Improve
Manageability/availability of
Large tables

Avoid data skew in
partitions

Maximize I/0 throughput

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List Partitioning
•Segmenting data with a list of values

•Flexible means of partitioning where data is better understood
Definition
• Similar to Range Partitioning, but without any max value

• CREATE TABLE DEPT_PART (DEPTNO NUMBER (2),DNAME VARCHAR2 (14),LOC
VARCHAR2 (13))
PARTITION BY LIST (DNAME)
(PARTITION D1_EAST VALUES (‘NEW YORK’),
Example
PARTITION D2_WEST VALUES (‘SAN FRANCISCO’, ‘LOS ANGELES’),
PARTITION D3_SOUTH VALUES (‘ATLANTA’,’DALLAS’,’HOUSTON’),
PARTITION D4_NORTH VALUES (‘CHICAGO’,’DETROIT’));

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Range ,List , Hash Partitions

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Composite Partitioning

A distinct value
Composite
pair for the two
Data is Partitioning is
dimensions
Partitioned complementary
uniquely
along two to multi
determines the
dimensions column range
target partition
partition

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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

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Range – List Partitioning

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Composite Partitioning
Table SALES Range - Range
RANGE(order_date)-RANGE(ship_date)

ship_date
• All records with
Jan order_date in
2006 ... ... March 2006
AND
Feb
ship_date in May
2006 ... ... 2006

... ...
May
May
2006 ... ...
... ...
Jan 2006 Feb 2006 Mar 2006
Mar 2006 Jan 2007
order_date

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Oracle Partitioning - A Concise Guide to Partition Types and Strategies

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