Over the past few years, there has been an explosion of many NoSQL database solutions and products. The meaning of the word "NoSQL" is not a campaign against the SQL language. In fact, OrientDB allows for SQL syntax! NoSQL is probably best described by the following:
NoSQL, meaning "not only SQL", is a movement encouraging developers and business people to open their minds and consider new possibilities beyond the classic relational approach to data persistence.
Alternatives to relational database management systems have existed for many years, but they have been relegated primarily to niche use cases such as telecommunications, medicine, CAD and others. Interest in NoSQL alternatives like OrientDB is increasing dramatically. Not surprisingly, many of the largest web companies like Google, Amazon, Facebook, Foursquare and Twitter are using NoSQL based solutions in their production environments.
What motivates companies to leave the comfort of a well established relational database world? It is basically the great need to better solve today's data problems. Specifically, there are a few key areas:
- Scalability (often huge)
- Smaller footprint
- Developer productivity and friendliness
- Schema flexibility
Most of these areas also happen to be the requirements of modern web applications. A few years ago, developers designed systems that could handle hundreds of concurrent users. Today it is not uncommon to have a potential target of thousands or millions of users connected and served at the same time.
Changing technology requirements have been taken into account on the application front by creating frameworks, introducing standards and leveraging best practices. However, in the database world, the situation has remained more or less the same for over 30 years. From the 1970s until recently, relational DBMSs have played the dominant role. Programming languages and methodologies have evolved, but the concept of data persistence and the DBMS have remained unchanged for the most part: it is all still tables, records and joins.
NoSQL-based solutions in general provide a powerful, scalable, and flexible way to solve data needs and use cases, which have previously been managed by relational databases. To summarize the NoSQL options, we'll examine the most common models or categories:
Key / Value databases: where the data model is reduced to a simple hash table, which consists of key / value pairs. It is often easily distributed across multiple servers. The most recognized products of this group include Redis, Dynamo, and Riak.
Column-oriented databases: where the data is stored in sections of columns offering more flexibility and easy aggregation. Facebook's Cassandra, Google's BigTable, and Amazon's SimpleDB are some examples of column-oriented databases.
Document databases: where the data model consists of document collections, in which each individual document can have multiple fields without necessarily having a defined schema. The best known products of this group are MongoDB and CouchDB.
Graph databases: where the domain model consists of vertices interconnected by edges creating rich graph structures. The best known products of this group are OrientDB, Neo4j and Titan.
OrientDB is a document-graph database, meaning it has full native graph capabilities coupled with features normally only found in document databases.
Each of these categories or models has its own peculiarities, strengths and limitations. There is no single category or model, which is better than the others. However, certain types of databases are better at solving specific problems. This leads to the motto of NoSQL: choose the best tool for your specific use case.
The goal of Orient Technologies in building OrientDB was to create a robust, highly scalable database that can perform optimally in the widest possible set of use cases. Our product is designed to be a fantastic "go to" solution for practically all of your data persistence needs. In the following parts of this tutorial, we will look closely at OrientDB, one of the best open-source, multi-model, next generation NoSQL products on the market today.