Token

As explained in ScyllaDB in Action

A token is a value used to determine a data partition's placement and ownership in a distributed database cluster.

A token is an integer position on a hash ring. ScyllaDB hashes each partition key to a token, placing rows with the same partition key together and assigning responsibility for that position to a node. section 3.3.1

Nodes claim token ranges around the ring, often through multiple virtual-node positions. When a node joins, it takes portions of existing ranges, and other nodes stream those rows to the new owner. section 3.3.1

During reads and inserts, ScyllaDB hashes the partition key, determines the applicable token, and forwards the request to the node that owns it. The TOKEN function exposes a partition's ring position. section 8.2.1

Inspecting a token

Use TOKEN(id) in cqlsh to display the ring position associated with each partition-key value: SELECT TOKEN(id), id FROM reviews.authors; section 8.2.1

Figure 3.8 Partitions are mapped to places on a hash ring.

A hash-ring figure makes the relationship between partition placement and token positions visible. section 3.3.1

How ScyllaDB in Action covers it

How deep it goes

Explains hashing, ring positions, vnode ownership, node joining, request routing, and TOKEN inspection without formal mathematics.

Examples

Uses hash-ring diagrams, vnode ownership illustrations, cluster status output, and a cqlsh TOKEN query.

What it assumes

Assumes partition keys and hashing, then connects them to distributed placement and ownership.

What you can do after

Apply the TOKEN function to inspect a partition key's ring position and trace which node owns its slice.

How it connects

Connects partition keys, hash rings, virtual nodes, replication factors, consistency options, and distributed data ownership.

liveBookmanning.com

Read ScyllaDB in Action on liveBook Get the book at manning.com

Related concepts

• language modelused by · A language model is a computational model that represents patterns in linguistic tokens to estimate sequence probabilities and predict or generate language from context.
• context windowmeasured by · A context window is the bounded sequence of tokens or other input information a model can access when processing or generating an output.
• sequencepart of · A sequence is an ordered collection of elements whose positions determine their order of traversal or processing.

This explainer was generated by Manning's knowledge graph from the text of ScyllaDB in Action. The section links point to the parts of the book it draws on.