<s>
Database	O
partitioning	O
is	O
normally	O
done	O
for	O
manageability	O
,	O
performance	O
or	O
availability	O
reasons	O
,	O
or	O
for	O
load	B-Application
balancing	I-Application
.	O
</s>
<s>
It	O
is	O
popular	O
in	O
distributed	B-Application
database	I-Application
management	I-Application
systems	I-Application
,	O
where	O
each	O
partition	O
may	O
be	O
spread	O
over	O
multiple	O
nodes	O
,	O
with	O
users	O
at	O
the	O
node	O
performing	O
local	O
transactions	O
on	O
the	O
partition	O
.	O
</s>
<s>
Current	O
high-end	O
relational	B-Application
database	I-Application
management	I-Application
systems	I-Application
provide	O
for	O
different	O
criteria	O
to	O
split	O
the	O
database	O
.	O
</s>
<s>
An	O
example	O
could	O
be	O
a	O
partition	O
for	O
all	O
rows	B-Application
where	O
the	O
"	O
zipcode	O
"	O
column	B-Application
has	O
a	O
value	O
between	O
70000	O
and	O
79999	O
.	O
</s>
<s>
It	O
distributes	O
tuples	B-Application
based	O
on	O
the	O
value	O
intervals	O
(	O
ranges	O
)	O
of	O
some	O
attribute	O
.	O
</s>
<s>
For	O
instance	O
,	O
a	O
query	O
with	O
a	O
predicate	O
“	O
A	O
between	O
A1	O
and	O
A2	O
”	O
may	O
be	O
processed	O
by	O
the	O
only	O
node(s )	O
containing	O
tuples	B-Application
.	O
</s>
<s>
For	O
example	O
,	O
all	O
rows	B-Application
where	O
the	O
column	B-Application
Country	O
is	O
either	O
Iceland	O
,	O
Norway	O
,	O
Sweden	O
,	O
Finland	O
or	O
Denmark	O
could	O
build	O
a	O
partition	O
for	O
the	O
Nordic	O
countries	O
.	O
</s>
<s>
Composite	O
partitioning	O
:	O
allows	O
for	O
certain	O
combinations	O
of	O
the	O
above	O
partitioning	O
schemes	O
,	O
by	O
for	O
example	O
first	O
applying	O
a	O
range	O
partitioning	O
and	O
then	O
a	O
hash	B-Error_Name
partitioning	O
.	O
</s>
<s>
Consistent	B-Algorithm
hashing	I-Algorithm
could	O
be	O
considered	O
a	O
composite	O
of	O
hash	B-Error_Name
and	O
list	O
partitioning	O
where	O
the	O
hash	B-Error_Name
reduces	O
the	O
key	O
space	O
to	O
a	O
size	O
that	O
can	O
be	O
listed	O
.	O
</s>
<s>
With	O
n	O
partitions	O
,	O
the	O
ith	O
tuple	B-Application
in	O
insertion	O
order	O
is	O
assigned	O
to	O
partition	O
(	O
i	O
mod	O
n	O
)	O
.	O
</s>
<s>
However	O
,	O
the	O
direct	O
access	O
to	O
individual	O
tuples	B-Application
,	O
based	O
on	O
a	O
predicate	O
,	O
requires	O
accessing	O
the	O
entire	O
relation	O
.	O
</s>
<s>
Hash	B-Error_Name
partitioning	O
:	O
applies	O
a	O
hash	B-Error_Name
function	I-Error_Name
to	O
some	O
attribute	O
that	O
yields	O
the	O
partition	O
number	O
.	O
</s>
<s>
The	O
partitioning	O
can	O
be	O
done	O
by	O
either	O
building	O
separate	O
smaller	O
databases	B-Application
(	O
each	O
with	O
its	O
own	O
tables	B-Application
,	O
indices	B-Data_Structure
,	O
and	O
transaction	B-General_Concept
logs	I-General_Concept
)	O
,	O
or	O
by	O
splitting	O
selected	O
elements	O
,	O
for	O
example	O
just	O
one	O
table	O
.	O
</s>
<s>
Horizontal	B-General_Concept
partitioning	I-General_Concept
involves	O
putting	O
different	O
rows	B-Application
into	O
different	O
tables	B-Application
.	O
</s>
<s>
The	O
two	O
partition	O
tables	B-Application
are	O
then	O
CustomersEast	O
and	O
CustomersWest	O
,	O
while	O
a	O
view	B-Language
with	O
a	O
union	B-Language
might	O
be	O
created	O
over	O
both	O
of	O
them	O
to	O
provide	O
a	O
complete	O
view	B-Language
of	O
all	O
customers	O
.	O
</s>
<s>
Vertical	O
partitioning	O
involves	O
creating	O
tables	B-Application
with	O
fewer	O
columns	O
and	O
using	O
additional	O
tables	B-Application
to	O
store	O
the	O
remaining	O
columns	O
.	O
</s>
<s>
Generally	O
,	O
this	O
practice	O
is	O
known	O
as	O
normalization	B-Application
.	O
</s>
<s>
This	O
type	O
of	O
partitioning	O
is	O
also	O
called	O
"	O
row	O
splitting	O
"	O
,	O
since	O
rows	B-Application
get	O
split	O
by	O
their	O
columns	O
,	O
and	O
might	O
be	O
performed	O
explicitly	O
or	O
implicitly	O
.	O
</s>
<s>
Creating	O
a	O
view	B-Language
across	O
the	O
two	O
newly	O
created	O
tables	B-Application
restores	O
the	O
original	O
table	O
with	O
a	O
performance	O
penalty	O
,	O
but	O
accessing	O
the	O
static	O
data	O
alone	O
will	O
show	O
higher	O
performance	O
.	O
</s>
<s>
A	O
columnar	B-General_Concept
database	I-General_Concept
can	O
be	O
regarded	O
as	O
a	O
database	O
that	O
has	O
been	O
vertically	O
partitioned	O
until	O
each	O
column	B-Application
is	O
stored	O
in	O
its	O
own	O
table	O
.	O
</s>
