Compression

Bit Packing / Mostly Encoding

Couchbase Server (Enterprise Edition) applies data compression to documents with open-source library Snappy. It provides three modes of compression.

• Off. The Couchbase Server decompresses the document if it is compressed, and stores the uncompressed document in memory but recompresses it when storing on disk. Couchbase server sends the document in uncompressed form.

• Passive. When Couchbase Server receives the compressed document, it stores the compressed document in memory and disk. Also, the documents are sent in compressed form.

• Active. Couchbase Server stores and sends compressed document even the document is uncompressed when it was received.

Checkpoints

Consistent Blocking

The replicator of Couchbase Server will checkpoint the source sequenceID corresponding to the last change sent to the target with a conflict resolver.

System Architecture

Shared-Nothing

Joins

Nested Loop Join

Couchbase Server supports lookup join, index join and ANSI join in its N1QL language.

Query Interface

Custom API

Couchbase Server uses a new language called N1QL which is a SQL for JSON for the query interface.

Data Model

Document / XML

The documents stored in Couchbase Server are in JSON or binary format.

Isolation Levels

Read Committed Serializable

Couchbase Server provides read committed isolation by default at the single document level. However, using the provided optimistic locking and pessimistic locking, user can obtain isolation of an individual document, to make sure that changes happen in the order that you expect.

Logging

Not Supported

Storage Organization

Sorted Files

Couchbase Server uses Couchstore to store core data operations. Each vBucket is represented as a separate Couchstore file in the file system. Couchstore uses a B+tree structure to quickly access items through their keys. Couchstore uses an append-only write model for efficient and safe writes.

Stored Procedures

Supported

"Prepared queries" is supported in Couchbase Server which is close to the Stored Procedures.

Storage Architecture

Disk-oriented

Query Compilation

Not Supported

Views

Materialized Views

Three views are supported by Couchbase Server: MapReduce views, Spatial views and Global Secondary Indexes (GSI) views.

• MapReduce views can be accessed via the View API.

• Spatial views can be accessed via the Spatial View API.

• N1QL queries with Global Secondary Indexes (GSI) and MapReduce views.

Indexes

B+Tree Skip List Hash Table Inverted Index (Full Text)

A few of indexes are available in Couchbase Server:

• Primary Index is based on on the unique key of every item in a specified bucket which contains a full set of keys in a given key space.

• Global Secondary Index (GSI) is the most frequently used index in Couchbase Server, for queries performed with the N1Ql query-language.
  The indexer for GSI creates a B+ tree for fast scans on the index key. Also, there is a Memory-Optimized GSI index which uses the skip-list structure as opposed to B-tree indexes.

• Full Text is provided by the Search Service and it contains targets derived from the textual contents of documents within one or more specified buckets.

• View: Supports Couchbase Views, with fields and information extracted from documents.

Concurrency Control

Optimistic Concurrency Control (OCC)

Couchbase Server offers both optimistic and pessimistic locking to guarantee concurrency.