Spanner is a

distributed SQL A distributed SQL database is a single relational database which replicates data across multiple servers. Distributed SQL databases are strongly consistent and most support consistency across racks, data centers, and wide area networks including c ...

database management and storage service developed by

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

. It provides features such as global transactions, strongly consistent reads, and automatic multi-site replication and failover. Spanner is used in Google F1, the database for its advertising business

Google Ads Google Ads, formerly known as Google Adwords, is an online advertising platform developed by Google, where advertisers bid to display brief advertisements, service offerings, product listings, and videos to web users. It can place ads in the res ...

, as well as Gmail and Google Photos.

Features

Spanner stores large amounts of mutable structured data. Spanner allows users to perform arbitrary queries using SQL with relational data while maintaining strong consistency and high availability for that data with synchronous replication. Key features of Spanner: * Transactions can be applied across rows, columns, tables, and databases within a Spanner universe. * Clients can control the replication and placement of data using automatic multi-site replication and failover. * Replication is synchronous and strongly consistent. * Reads are strongly consistent and data is versioned to allow for stale reads: clients can read previous versions of data, subject to garbage collection windows. * Supports a native SQL interface for reading and writing data.

History

Spanner was first described in 2012 for internal Google data centers. Spanner's SQL capability was added in 2017 and documented in a

SIGMOD SIGMOD is the Association for Computing Machinery's Special Interest Group on Management of Data, which specializes in large-scale data management problems and databases. The annual ACM SIGMOD Conference, which began in 1975, is considered one of ...

2017 paper. It became available as part of

Google Cloud Platform Google Cloud Platform (GCP) is a suite of cloud computing services offered by Google that provides a series of modular cloud services including computing, Computer data storage, data storage, Data analysis, data analytics, and machine learnin ...

in 2017, under the name "Cloud Spanner".

Architecture

Spanner uses the

Paxos algorithm Paxos is a family of protocols for solving Consensus (computer science), consensus in a network of unreliable or fallible processors. Consensus is the process of agreeing on one result among a group of participants. This problem becomes difficult ...

as part of its operation to

shard Shard or sherd is a sharp piece of glass, pottery or stone. Shard may also refer to: Places * Shard End, a place in Birmingham, United Kingdom Architecture * Dresden Shard, a redesign of the Bundeswehr Military History Museum in Dresden, German ...

(partition) data across up to hundreds of servers. It makes heavy use of hardware-assisted

clock synchronization Clock synchronization is a topic in computer science and engineering that aims to coordinate otherwise independent clocks. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift, caused by clocks ...

using GPS clocks and

atomic clock An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...

s to ensure

global consistency Data inconsistency refers to whether the same data kept at different places do or do not match. Point-in-time consistency Point-in-time consistency is an important property of backup files and a critical objective of software that creates backups. ...

. TrueTime is the brand name for Google's distributed cloud infrastructure, which provides Spanner with the ability to generate monotonically increasing timestamps in data centers around the world. Google's F1 SQL

database management system In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and an ...

(DBMS) is built on top of Spanner, replacing Google's custom

MySQL MySQL () is an Open-source software, open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A rel ...

variant.

References

Bibliography

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Features

History

Architecture

References

Bibliography

Further reading