A keyspace (or key space) in a

NoSQL A NoSQL (originally referring to "non- SQL" or "non-relational") database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Such databases have existed ...

data store In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. ...

is an object that holds together all

column families {{Short description, A database project that organizes data in packed columns A column family is a database object that contains columns of related data. It is a tuple (pair) that consists of a key–value pair, where the key is mapped to a value t ...

of a design. It is the outermost grouping of the data in the data store. It resembles the

schema The word schema comes from the Greek word ('), which means ''shape'', or more generally, ''plan''. The plural is ('). In English, both ''schemas'' and ''schemata'' are used as plural forms. Schema may refer to: Science and technology * SCHEMA ...

concept in

Relational database management system A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relatio ...

s. Generally, there is one keyspace per application.

Structure

A keyspace may contain

super column A super column is a tuple (a pair) with a binary super column name and a value that maps it to many columns. They consist of a key–value pairs, where the values are columns. Theoretically speaking, super columns are ( sorted) associative array o ...

s. Each super column contains one or more column families, and each column family contains at least one column. The keyspace is the highest abstraction in a

distributed data store A distributed data store is a computer network where information is stored on more than one node, often in a replicated fashion. It is usually specifically used to refer to either a distributed database where users store information on a ''numb ...

. This is fundamental in preserving the structural heuristics in dynamic data retrieval. Multiple relay protocol algorithms are integrated within the simple framework.

Comparison with relational database systems

The keyspace has similar importance like a

has in a database. In contrast to the schema, however, it does not stipulate any concrete structure, like it is known in the entity-relationship model used widely in the

relational data model The relational model (RM) is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tu ...

s. For instance, the contents of the keyspace can be column families, each having different number of columns, or even different columns. So, the column families that somehow relate to the

row Row or ROW may refer to: Exercise *Rowing, or a form of aquatic movement using oars *Row (weight-lifting), a form of weight-lifting exercise Math *Row vector, a 1 × ''n'' matrix in linear algebra. *Row (database), a single, implicitly structured ...

concept in relational databases do not stipulate any fixed structure. The only point that is the same with a schema is that it also contains a number of "objects", which are tables in RDBMS systems and here column families or super columns. So, in distributed data stores, the whole burden to handle rows that may even change from data-store update to update lies on the shoulders of the programmers.

Examples

As an example, we show a number of column families in a keyspace. The CompareWith keyword defines how the column comparison is made. In the example, the

UTF-8 UTF-8 is a variable-width encoding, variable-length character encoding used for electronic communication. Defined by the Unicode Standard, the name is derived from ''Unicode'' (or ''Universal Coded Character Set'') ''Transformation Format 8-bit'' ...

standard has been selected. Other ways of comparison exist, such as AsciiType, BytesType, LongType, TimeUUIDType. 0.01 Another example shows a simplified

Twitter Twitter is an online social media and social networking service owned and operated by American company Twitter, Inc., on which users post and interact with 280-character-long messages known as "tweets". Registered users can post, like, and ...

clone data model: 0.01

References

{{reflist

External links

Cassandra – Getting Started (Java)
Distributed data stores NoSQL