<s>
ClickHouse	B-Language
is	O
an	O
open-source	B-Application
column-oriented	B-General_Concept
DBMS	I-General_Concept
(	O
columnar	B-General_Concept
database	I-General_Concept
management	O
system	O
)	O
for	O
online	B-Application
analytical	I-Application
processing	I-Application
(	O
OLAP	B-Application
)	O
that	O
allows	O
users	O
to	O
generate	O
analytical	O
reports	O
using	O
SQL	B-Language
queries	B-Language
in	O
real-time	O
.	O
</s>
<s>
ClickHouse	B-Language
Inc	O
.	O
is	O
headquartered	O
in	O
the	O
Bay	O
Area	O
of	O
California	O
,	O
United	O
States	O
with	O
the	O
subsidiary	O
,	O
ClickHouse	B-Language
B.V.	O
,	O
based	O
in	O
Amsterdam	O
,	O
Netherlands	O
.	O
</s>
<s>
In	O
September	O
2021	O
in	O
San	O
Francisco	O
,	O
CA	O
,	O
ClickHouse	B-Language
incorporated	O
to	O
house	O
the	O
open	O
source	O
technology	O
with	O
an	O
initial	O
$50	O
million	O
investment	O
from	O
Index	O
Ventures	O
and	O
Benchmark	O
Capital	O
with	O
participation	O
by	O
Yandex	O
N.V.	O
and	O
others	O
.	O
</s>
<s>
ClickHouse	B-Language
’s	O
technology	O
was	O
first	O
developed	O
over	O
10	O
years	O
ago	O
at	O
Yandex	O
,	O
Russia	O
's	O
largest	O
technology	O
company	O
.	O
</s>
<s>
The	O
developers	O
spent	O
3	O
years	O
to	O
prove	O
this	O
hypothesis	O
,	O
and	O
in	O
2012	O
ClickHouse	B-Language
launched	O
in	O
production	O
for	O
the	O
first	O
time	O
to	O
power	O
Yandex.Metrica	B-Protocol
,	O
the	O
second-largest	O
web	O
analytics	O
platform	O
in	O
the	O
world	O
,	O
after	O
Google	O
Analytics	O
.	O
</s>
<s>
Unlike	O
custom	O
data	O
structures	O
used	O
before	O
,	O
ClickHouse	B-Language
was	O
applicable	O
more	O
generally	O
to	O
work	O
as	O
a	O
database	O
management	O
system	O
.	O
</s>
<s>
The	O
power	O
and	O
utility	O
of	O
ClickHouse	B-Language
offered	O
a	O
true	O
column-oriented	B-General_Concept
DBMS	I-General_Concept
,	O
it	O
allowed	O
for	O
systems	O
to	O
generate	O
reports	O
from	O
petabytes	O
of	O
raw	O
data	O
with	O
sub-second	O
latencies	O
.	O
</s>
<s>
ClickHouse	B-Language
was	O
widely	O
adopted	O
at	O
Yandex	O
including	O
for	O
Yandex.Tank	O
load	O
testing	O
tool	O
and	O
Yandex.Market	O
to	O
monitor	O
site	O
accessibility	O
and	O
KPIs	O
.	O
</s>
<s>
In	O
2016	O
,	O
the	O
ClickHouse	B-Language
project	O
was	O
released	O
as	O
open-source	B-Application
software	I-Application
under	O
the	O
Apache	B-Application
2	I-Application
license	I-Application
in	O
June	O
2016	O
to	O
power	O
analytical	O
use	O
cases	O
around	O
the	O
globe	O
.	O
</s>
<s>
The	O
systems	O
at	O
the	O
time	O
offered	O
a	O
server	O
throughput	O
of	O
a	O
hundred	O
thousand	O
rows	O
per	O
second	O
,	O
ClickHouse	B-Language
out	O
performed	O
that	O
speed	O
with	O
a	O
throughput	O
of	O
hundreds	O
of	O
millions	O
of	O
rows	O
per	O
second	O
.	O
</s>
<s>
Since	O
ClickHouse	B-Language
became	O
available	O
as	O
open	O
source	O
in	O
2016	O
,	O
its	O
popularity	O
has	O
grown	O
exponentially	O
,	O
as	O
evidenced	O
through	O
adoption	O
by	O
industry-leading	O
companies	O
like	O
Uber	O
,	O
Comcast	O
,	O
eBay	O
,	O
and	O
Cisco	O
.	O
</s>
<s>
ClickHouse	B-Language
was	O
also	O
implemented	O
at	O
CERN	O
's	O
LHCb	O
experiment	O
to	O
store	O
and	O
process	O
metadata	O
on	O
10	O
billion	O
events	O
with	O
over	O
1000	O
attributes	O
per	O
event	O
.	O
</s>
<s>
The	O
main	O
features	O
of	O
the	O
ClickHouse	B-Language
DBMS	O
are	O
:	O
</s>
<s>
True	O
column-oriented	B-General_Concept
DBMS	I-General_Concept
.	O
</s>
<s>
ClickHouse	B-Language
uses	O
asynchronous	O
multi-master	O
replication	O
.	O
</s>
<s>
ZooKeeper	O
is	O
used	O
for	O
coordinating	O
processes	O
,	O
but	O
it	O
's	O
not	O
involved	O
in	O
query	B-Language
processing	O
and	O
execution	O
.	O
</s>
<s>
SQL	B-Language
support	O
.	O
</s>
<s>
ClickHouse	B-Language
supports	O
an	O
extended	O
SQL-like	O
language	O
that	O
includes	O
arrays	O
and	O
nested	O
data	O
structures	O
,	O
approximate	O
and	O
URI	B-Protocol
functions	O
,	O
and	O
the	O
availability	O
to	O
connect	O
an	O
external	O
key-value	O
store	O
.	O
</s>
<s>
This	O
approach	O
allows	O
it	O
to	O
achieve	O
high	O
CPU	B-General_Concept
performance	O
.	O
</s>
<s>
Parallel	O
and	O
distributed	O
query	B-Language
processing	O
is	O
available	O
(	O
including	O
JOINs	B-Language
)	O
.	O
</s>
<s>
Hard	B-Device
disk	I-Device
drive	I-Device
(	O
HDD	O
)	O
optimization	O
.	O
</s>
<s>
The	O
system	O
can	O
process	O
data	O
that	O
does	O
n't	O
fit	O
in	O
random-access	B-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
.	O
</s>
<s>
Database	O
connection	O
options	O
include	O
the	O
console	O
client	O
,	O
the	O
HTTP	B-Protocol
API	B-Application
,	O
or	O
one	O
of	O
the	O
wrappers	B-Library
(	O
wrappers	B-Library
are	O
available	O
for	O
Python	B-Language
,	O
PHP	B-Application
,	O
NodeJS	B-Language
,	O
Perl	B-Language
,	O
Ruby	B-Language
and	O
R	B-Language
)	O
.	O
</s>
<s>
ODBC	O
driver	O
and	O
JDBC	B-Application
driver	I-Application
are	O
also	O
available	O
for	O
ClickHouse	B-Language
.	O
</s>
<s>
ClickHouse	B-Language
has	O
some	O
features	O
that	O
can	O
be	O
considered	O
disadvantages	O
:	O
</s>
<s>
There	O
is	O
no	O
support	O
for	O
transactions	B-General_Concept
.	O
</s>
<s>
ClickHouse	B-Language
was	O
designed	O
for	O
OLAP	B-Application
queries	B-Language
.	O
</s>
<s>
Queries	B-Language
can	O
use	O
a	O
large	O
number	O
of	O
rows	O
extracted	O
from	O
the	O
DB	O
,	O
but	O
only	O
a	O
small	O
subset	O
of	O
columns	O
.	O
</s>
<s>
Queries	B-Language
are	O
relatively	O
rare	O
(	O
usually	O
around	O
100	O
RPS	O
per	O
server	O
)	O
.	O
</s>
<s>
For	O
simple	O
queries	B-Language
,	O
latencies	O
of	O
about	O
50	O
ms	O
are	O
allowed	O
.	O
</s>
<s>
Column	O
values	O
are	O
fairly	O
small	O
,	O
usually	O
consisting	O
of	O
numbers	O
and	O
short	O
strings	O
(	O
for	O
example	O
,	O
60	O
bytes	B-Application
per	O
URL	O
)	O
.	O
</s>
<s>
High	O
throughput	O
is	O
required	O
when	O
processing	O
a	O
single	O
query	B-Language
(	O
up	O
to	O
billions	O
of	O
rows	O
per	O
second	O
per	O
server	O
)	O
.	O
</s>
<s>
A	O
query	B-Language
result	O
is	O
mostly	O
filtered	O
or	O
aggregated	O
.	O
</s>
<s>
Data	O
update	O
uses	O
a	O
simple	O
scenario	O
(	O
usually	O
batch-only	O
,	O
without	O
complicated	O
transactions	B-General_Concept
)	O
.	O
</s>
<s>
One	O
of	O
the	O
common	O
cases	O
for	O
ClickHouse	B-Language
is	O
server	O
log	O
analysis	O
.	O
</s>
<s>
After	O
setting	O
regular	O
data	O
uploads	O
to	O
ClickHouse	B-Language
(	O
it	O
's	O
recommended	O
to	O
insert	O
data	O
in	O
fairly	O
large	O
batches	O
with	O
more	O
than	O
1000	O
rows	O
)	O
,	O
it	O
's	O
possible	O
to	O
analyze	O
incidents	O
with	O
instant	O
queries	B-Language
or	O
monitor	O
a	O
service	O
's	O
metrics	O
,	O
such	O
as	O
error	O
rates	O
,	O
response	O
times	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
ClickHouse	B-Language
can	O
also	O
be	O
used	O
as	O
an	O
internal	O
data	O
warehouse	O
for	O
in-house	O
analysts	O
.	O
</s>
<s>
ClickHouse	B-Language
can	O
store	O
data	O
from	O
different	O
systems	O
(	O
such	O
as	O
Hadoop	B-Application
or	O
certain	O
logs	O
)	O
and	O
analysts	O
can	O
build	O
internal	O
dashboards	O
with	O
the	O
data	O
or	O
perform	O
real-time	O
analysis	O
for	O
business	O
purposes	O
.	O
</s>
<s>
According	O
to	O
benchmark	O
tests	O
conducted	O
by	O
its	O
developers	O
,	O
for	O
OLAP	B-Application
queries	B-Language
ClickHouse	B-Language
is	O
more	O
than	O
100	O
times	O
faster	O
than	O
Hive	B-General_Concept
(	O
a	O
DBMS	O
based	O
on	O
the	O
Hadoop	B-Application
technology	O
stack	O
)	O
or	O
MySQL	B-Application
(	O
a	O
common	O
RDBMS	B-Application
)	O
.	O
</s>
