NOSQL OVERVIEW

NOSQL DATABASES

• A cheeky acronym for Not Only SQL

• More confrontationally, No to SQL.

THE RISE OF NOSQL DATABASES

TYPES OF NOSQL DATABASES

DOCUMENT STORES

• Reply on indexes to facilitate access to documents based on their attributes.

DOCUMENT STORES• Data model of a document store is one

of disconnected entities

• Should scale horizontally, as there’s no contended state between mutually independent records at write time

• Limitation: Transactions are limited to the level of an individual record.

• Support for operating across sets of documents atomically is emerging

KEY VALUE STORES

• Large, distributed hash map data structures that store and retrieve opaque values by key

• Level of insight offered into data is due to data opacity.

• To retrieve insight across individual records, a cluster computing framework like Map reduce or spark is used.

KEY-VALUE STORES1.Key = Domain specific identifier

2.Key is hashed with a uniform distribution hash function.

3.Hashed key is used to store values in a corresponding bucket.

4.A similar procedure is used to retrieve data.

5.For fault tolerance each bucket is replicated onto several machines.

COLUMN FAMILY

• Modelled on Google’s BigTable.

• Logically speaking, it’s just a map of maps.

COLUMN FAMILY

• Simplest storage unit: Column consisting of name value pair.

• Super column: Sorted set of columns with a name.

COLUMN FAMILY• Columns are stored in rows, and when a row contains

columns only, it is known as a column family.

• When a row contains super columns, it is known as a super column family.

COLUMN FAMILY• In a column family database, each row in the table represents a

particular overarching entity. They are containers for related pieces of data.

COLUMN FAMILY

• Where each row gives a complete view of one entity, the column view naturally indexes particular aspects across the whole dataset.

GRAPH DATABASES• It contains nodes and relationships.

• Nodes contain properties (key-value pairs).

• Nodes can be labeled with one or more labels.

• Relationships are named and directed, and always have a start and end node.

• Relationships can also contain properties.

GRAPH DATABASES• Don’t depend heavily on

indexes because the graph itself provides a natural adjacency index

• Relationships attached to a node naturally provide a direct connection to other related nodes of interest.

• Graph queries use this locality to traverse through the graph by chasing pointers.