Relational databases store data in tables
- 2. Types of NoSQL Databases
- 3. Introduction • It’s born out of a need to handle larger data volumes which forced a fundamental shift to building large hardware platforms through clusters of commodity servers. • Advocates of NoSQL databases claim that they can build systems that are more performant, scale much better, and are easier to program with.
- 4. Why Are NoSQL Databases Interesting? • Application development productivity. A lot of application development effort is spent on mapping data between in-memory data structures and a relational database. • A NoSQL database may provide a data model that better fits the application’s needs, thus simplifying that interaction and resulting in less code to write, debug, and evolve.
- 5. Cont’d • Large-scale data. Organizations are finding it valuable to capture more data and process it more quickly. • They are finding it expensive, if even possible, to do so with relational databases. • The primary reason is that a relational database is designed to run on a single machine, but it is usually more economic to run large data and computing loads on clusters of many smaller and cheaper machines. • Many NoSQL databases are designed explicitly to run on clusters, so they make a better fit for big data scenarios.
- 6. The Value of Relational Databases • Getting at Persistent Data – provide a “backing” store for volatile memory – 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 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.
- 7. Concurrency • Multiple applications accessing shared data – Transactions • 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..
- 8. 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.
- 9. Impedance Mismatch • Impedance mismatch is a term used in computer science to describe the problem that arises when two systems or components that are supposed to work together have different data models, structures, or interfaces that make communication difficult or inefficient. • In the context of databases, impedance mismatch refers to the discrepancy between the object-oriented programming (OOP) model used in application code and the relational model used in database management systems (DBMS). • While OOP models are designed to represent data as objects with properties and methods, relational models represent data as tables with columns and rows. • This impedance mismatch can create challenges when it comes to mapping objects in code to tables in a database or vice versa.
- 10. 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. • Structure and relationships have to be mapped – Rich, in-memory structures have to be translated to relational representation to be stored on disk – Translation: impedance mismatch
- 11. Cont’d
- 12. Cont’d • Impedance mismatch has been made much easier to deal with by the wide availability of object relational mapping frameworks. • Impedance mismatch has been made much easier to deal with by the wide availability of object relational mapping frameworks, such as Hibernate and iBATIS that implement well- known mapping patterns but the mapping problem is still an issue.
- 13. Application and Integration Databases • Data integration is the process of taking data from different sources and formats and combining it into a single data set. • Integration database - with multiple applications, usually developed by separate teams, storing their data in a common database. • This improves communication because all the applications are operating on a consistent set of persistent data. Or • An integration database is a database which acts as the data store for multiple applications, and thus integrates data across these applications .
- 14. Cont’d
- 15. Cont’d Integrate many applications becomes (dramatically) more complexthan any single application needs −Changes to the data model must be coordinated −Different structural and performance needs for different applications −Database integrity becomes an issue Instead, treat the database as an application database −Single application, single development team −Provide alternate integration mechanisms
- 16. Cont’d • Data integration platforms are an efficient approach to data utilization and storage. • Rather than replicating data across locations or environments, the integration database serves as a single source of truth.
- 17. During the 2000s we saw a distinct shift to web services where applications would communicate over HTTP. Alternate Integration Mechanism: Services More recent push to use Web Services where applications integrate over HTTP communications −XML-RPC, SOAP, REST ∙Results in more flexibility for exchange data structure −XML, JSON, etc. −Text-based protocols ∙Results in letting application developers choose database −Application databases −Relational databases are often still an appropriate choice
- 18. Application Database • Application Database for a database that is controlled and accessed by a single application. • With an application database, only the team using the application needs to know about the database structure, which makes it much easier to maintain and evolve the schema. • Since the application team controls both the database and the application code, the responsibility for database integrity can be put in the application code.
- 19. The Attack of the Clusters The 2000s saw the web grow enormously −Web use tracking data, social networks, activity logs, mapping data, etc. −Huge websites serving huge numbers of visitors ∙To handle the increase in data and traffic required more computing resources ∙Instead of building bigger machines with more processors, storage, and memory, use clusters of small, commodity machines −Cheaper, more resilient ∙But relational databases are not designed to be run on clusters
- 20. Cont’d • Coping with the increase in data and traffic required more computing resources. • To handle this kind of increase, you have two choices: • 1. Scaling up implies: – bigger machines – more processors – more disk storage – more memory • Scaling up disadvantages: – But bigger machines get more and more expensive. – There are real limits as size increases.
- 21. Cont’d • Use lots of small machines in a cluster: – A cluster of small machines can use commodity hardware and ends up being cheaper at these kinds of scales. – It can also be more resilient—while individual machine failures are common, the overall cluster can be built to keep going despite such failures, providing high reliability.
- 22. Clustered Relational Databases • Relational databases are not designed to be run on Clusters. • Clustered relational databases, such as the Oracle RAC or Microsoft SQL Server, work on the concept of a shared disk subsystem where cluster still has the disk subsystem as a single point of failure. • Relational databases could also be run as separate servers for different sets of data, effectively sharding the database. • Even though this separates the load, all the sharding has to be controlled by the application which has to keep track of which database server to talk to for each bit of data.
- 23. Cont’d • We lose any querying, referential integrity, transactions, or consistency controls that cross shards. • Commercial relational databases (licensed) are usually priced on a single-server assumption, so running on a cluster raised prices. • This mismatch between relational databases and clusters led some organization to consider an alternative route to data storage. Two companies in particular – 1. Google – 2.Amazon • Both were running large clusters • They were capturing huge amounts of data
- 24. The Emergence of NoSQL • Historical note: ‘NoSQL’ was first used to name an open-source relational database development led by Carlo Strozzi. • Current use of the phrase came from a conference meet up discussing “open-source, distributed, nonrelational databases. • The name NoSQL comes from the fact that the NoSQL databases doesn’t use SQL as a query language. • Instead, the database is manipulated through shell scripts that can be combined into the usual UNIX pipelines.
- 25. Cont’d • Most NoSQL databases are driven by the need to run on clusters. • Relational databases use ACID transactions to handle consistency across the whole database. • This inherently clashes with a cluster environment, so NoSQL databases offer a range of options for consistency and distribution. • Not all NoSQL databases are strongly oriented towards running on clusters. • Graph databases are one style of NoSQL databases that uses a distribution model similar to relational databases but offers a different data model that makes it better at handling data with complex relationships.
- 26. Cont’d • NoSQL databases operate without a schema, allowing you to freely add fields to database records without having to define any changes in structure first. • Two primary reasons for considering NoSQL: – 1) To handle data access with sizes and performance that demand a cluster – 2) To improve the productivity of application development by using a more convenient data interaction style.
- 27. Cont’d • A NoSQL is a database that provides a mechanism for storage and retrieval of data, they are used in real-time web applications and big data and their use are increasing over time. • Many NoSQL stores compromise consistency in favor of availability, speed and partition tolerance.
- 28. Advantages of NoSQL • 1. High Scalability – NoSQL databases use sharding for horizontal scaling. – It can handle huge amount of data because of scalability, as the data grows NoSQL scale itself to handle that data in efficient manner. • 2. High Availability – Auto replication feature in NoSQL databases makes it highly available.
- 29. Disadvantages of NoSQL 1. Narrow Focus: It is mainly designed for storage, but it provides very little functionality. 2. Open Source: NoSQL is open-source database that is two database systems are likely to be unequal. 3. Management Challenge: Big data management in NoSQL is much more complex than a relational database. 4. GUI is not available: GUI mode tools to access the database is not flexibly available in the market. 5. Backup: it is a great weak point for some NoSQL databases like MongoDB. 6. Large Document size: Data in JSON format increases the document size.
- 30. When should NoSQL be used • When huge amount of data need to be stored and retrieved. • The relationship between data you store is not that important. • The data changing over time and is not structured. • Support of constraint and joins is not required at database level. • The data is growing continuously and you need to scale the database regular to handle the data.
- 31. Characteristics of NoSQL Databases They do not use SQL and the relational model • Some do have query languages which are similar to SQL to be easy to learn and use. ∙ Mostly open-source projects ∙Designed to be distributed –clustered −No expectation of ACID properties −Range of options for consistency and distribution ∙Schema free −Freely add fields to records without having to define any changes in structure first −Non-uniform data and custom fields ∙A no Definition of NoSQL: An ill-defined set of mostly open- source databases, mostly developed in the early 21stcentury, and mostly not using SQL
- 32. Polyglot Persistence • Polyglot persistence is a conceptual term that refers to the use of different data storage approaches and technologies to support the unique storage requirements of various data types that live within enterprise applications. • Polyglot persistence refers to using different data storage technologies to handle varying data storage needs. • Polyglot Persistence is a fancy term to mean that when storing data, it is best to use multiple data storage technologies, chosen based upon the way data is being used by individual applications or components of a single application. • Different kinds of data are best dealt with different data stores. In short, it means picking the right tool for the right use case.
- 33. Example • Looking at a Polyglot Persistence example, an e-commerce platform will deal with many types of data (i.e. shopping cart, inventory, completed orders, etc). Instead of trying to store all this data in one database, which would require a lot of data conversion to make the format of the data all the same, store the data in the database best suited for that type of data. So the e-commerce platform might look like this:
- 34. Cont’d
- 35. Cont’d
- 36. Cont’d