<s>
Spanner	B-Operating_System
is	O
a	O
distributed	B-Language
SQL	I-Language
database	B-Application
management	I-Application
and	O
storage	O
service	O
developed	O
by	O
Google	B-Application
.	I-Application
</s>
<s>
Spanner	B-Operating_System
is	O
used	O
in	O
Google	B-Operating_System
F1	I-Operating_System
,	O
the	O
database	O
for	O
its	O
advertising	O
business	O
Google	B-Application
Ads	I-Application
.	O
</s>
<s>
Spanner	B-Operating_System
stores	O
large	O
amounts	O
of	O
mutable	O
structured	O
data	O
.	O
</s>
<s>
Spanner	B-Operating_System
allows	O
users	O
to	O
perform	O
arbitrary	O
queries	O
using	O
SQL	O
with	O
relational	O
data	O
while	O
maintaining	O
strong	O
consistency	O
and	O
high	O
availability	O
for	O
that	O
data	O
with	O
synchronous	O
replication	O
.	O
</s>
<s>
Key	O
features	O
of	O
Spanner	B-Operating_System
:	O
</s>
<s>
Transactions	O
can	O
be	O
applied	O
across	O
rows	O
,	O
columns	O
,	O
tables	O
,	O
and	O
databases	B-Application
within	O
a	O
Spanner	B-Operating_System
universe	O
.	O
</s>
<s>
Spanner	B-Operating_System
was	O
first	O
described	O
in	O
2012	O
for	O
internal	O
Google	B-Architecture
data	I-Architecture
centers	I-Architecture
.	O
</s>
<s>
Spanner	B-Operating_System
's	O
SQL	O
capability	O
was	O
added	O
in	O
2017	O
and	O
documented	O
in	O
a	O
SIGMOD	O
2017	O
paper	O
.	O
</s>
<s>
It	O
became	O
available	O
as	O
part	O
of	O
Google	B-General_Concept
Cloud	I-General_Concept
Platform	I-General_Concept
in	O
2017	O
,	O
under	O
the	O
name	O
"	O
Cloud	O
Spanner	B-Operating_System
"	O
.	O
</s>
<s>
Spanner	B-Operating_System
uses	O
the	O
Paxos	B-Operating_System
algorithm	I-Operating_System
as	O
part	O
of	O
its	O
operation	O
to	O
shard	B-General_Concept
(	O
partition	O
)	O
data	O
across	O
up	O
to	O
hundreds	O
of	O
servers	O
.	O
</s>
<s>
It	O
makes	O
heavy	O
use	O
of	O
hardware-assisted	O
clock	O
synchronization	O
using	O
GPS	O
clocks	O
and	O
atomic	O
clocks	O
to	O
ensure	O
global	B-General_Concept
consistency	I-General_Concept
.	O
</s>
<s>
TrueTime	O
is	O
the	O
brand	O
name	O
for	O
Google	B-Application
's	I-Application
distributed	O
cloud	O
infrastructure	O
,	O
which	O
provides	O
Spanner	B-Operating_System
with	O
the	O
ability	O
to	O
generate	O
monotonically	O
increasing	O
timestamps	O
in	O
datacenters	O
around	O
the	O
world	O
.	O
</s>
<s>
Google	B-Application
's	I-Application
F1	B-Operating_System
SQL	O
database	B-Application
management	I-Application
system	I-Application
(	O
DBMS	O
)	O
is	O
built	O
on	O
top	O
of	O
Spanner	B-Operating_System
,	O
replacing	O
Google	B-Application
's	I-Application
custom	O
MySQL	B-Application
variant	O
.	O
</s>
