Introduction to NoSQL Databases and Types of NOSQL Databases.pptx
- 1. Why NoSQL? • Relational databases have been the default choice for serious data storage, especially in the world of enterprise applications your only choice can be which relational database to use. • After such a long period of dominance, the current excitement about NoSQL databases comes as a surprise. • Now we’ll explore why relational databases
- 2. The Value of Relational Databases 1. Getting at Persistent Data Two areas of memory: • Fast, small, volatile main memory • Larger, slower, non volatile backing store • Since main memory is volatile to keep data around, we write it to a backing store, commonly seen a disk which can be persistent memory. The backing store can be: • File system • Database
- 3. • The database allows more flexibility than a file system in storing large amounts of data in a way that allows an application program to get information quickly and easily. 2. Concurrency • Enterprise applications tend to have many people using same data at once, possibly modifying that data. We have to worry about coordinating interactions between them to avoid things like double booking of hotel rooms. • Since enterprise applications can have lots of users and other systems all working concurrently, there’s a lot of room for bad things to happen. Relational databases help to handle this by controlling all access to their data through transactions.
- 4. 3. Integration • Enterprise requires multiple applications, written by different teams, to collaborate in order to get things done. Applications often need to use the same data and updates made through one application have to be visible to others. • A common way to do this is shared database integration where multiple applications store their data in a single database. • Using a single database allows all the applications to use each others’ data easily, while the database’s concurrency control handles multiple applications in the same way as it handles multiple users in a single application.
- 5. 4. A (Mostly) Standard Model • Relational databases have succeeded because they provide the core benefits in a (mostly) standard way. • As a result, developers can learn the basic relational model and apply it in many projects. • Although there are differences between different relational databases, the core mechanisms remain the same.
- 6. Impedance Mismatch • For Application developers using relational databases, the biggest frustration has been what’s commonly called the impedance mismatch: the difference between the relational model and the in-memory data structures. • The relational data model organizes data into a structure of tables. Where a tuple is a set of name-value pairs and a relation is a set of tuples. • The values in a relational tuple have to be simple—they cannot contain any structure, such as a nested record or a list. This limitation isn’t true for in-memory data structures, which can take on much richer structures than relations. • So if you want to use a richer in-memory data structure, you have to translate it to a relational representation to store it on disk. Hence the impedance mismatch—two different representations that require translation.