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Strategies For Migrating From SQL to NoSQL Database

  • Last Updated : 07 Jan, 2022

Traditionally in many software projects, we might have used RDBMS like Oracle, SQL Server, MySQL, etc., and we might have used Structured Query Language(SQL) to support the transactions. Nowadays NoSQL Database is frequently used in many places even as a solo software or with a mix of RDBMS and NoSQL software. In this article, let us see the strategies for migrating from SQL to NoSQL Database.

Advantages of NoSQL Database:

  1. Freedom from relational model involving with strict relationships like Foreign Key, relationships to other tables using Joins, Object-relational mapping, etc., Instead Document-based NoSQL database like MongoDB, CouchDB, etc., supports encapsulation and can achieve the similar nature of RDBMS facility.
  2. Storing data in the form of an array of integers, as a single entity, etc., easily helps to reduce complex joins to bring the output.
  3. Regarding the optimization concept, the RavenDB kind of NoSQL database supports the indexing feature which quickly helps to pull the data.
  4. Like the RDBMS database, the NoSQL database does not support int datatype for unique identification, but it supports String keys. Because of this reason, a few other String keys are also used and they helped in the reduction of queries and also in faster lookups. A classic example is no two users can have a unique email id. By using the String keys concept, the login process is made simple which avoids many complex query processes.
  5. RavenDB kind of NoSQL database support relationship. A smooth kind of transition to NoSQL is possible even without not using relationships and complex joins.

Alternative solutions that are available in NoSQL to support the useful features of RDBMS

  1. Important concepts of ACID i.e. Atomic(A), Consistent(C), Isolated(I), Durable(D) are seen in RavenDB kind of NoSQL database.  Especially in, transactions are supported and atomic writes are possible.
  2. Performance is possible in NoSQL via different concepts like denormalization. Instead of creating the complex primary key and foreign key relationships and creating complex joins to retrieve the data, whole data is placed in a single document. For example, a post in GFG places the article’s content, comments, likes, and shares for it all together in a single document or collection to help to retrieve the data very fastly.
  3. Consistency is a very important feature of RDBMS. In NoSQL, It can be achieved by means of BASE(i.e. Basically Available, Soft State, and Eventually Consistent). RavenDB kind of NoSQL supports Writes are ACID/Reads by ID are ACID but queries are BASE. It supports WaitForIndexesAfterSaveChanges() which obviously makes RavenDB block other transactions until a COMMIT is finished and necessary changes are updated. Even it has WaitForNonStaleResults methods also to support consistency. In MongoDB, the same can be achieved by blocking writes but it supports updating

Important Factors While Migrating from SQL to NoSQL:

Some of the important factors that need to be looked at for migrating from SQL to NoSQL:

1. Redesign the Schema: Only data layer and schema need to be changed according to a NoSQL-optimized model. In business logic, no changes are required. 

2. Refactorization: Data logic and RDBMS schema need to be refactored into a NoSQL-optimized model.

3. Host it first and optimization process to be done on a need basis: In the proposed technology, hosting has to occur and on top of it, if required, optimize the process for better performance.

Few Terminologies:

Few terminologies need to be seen in NoSQL which is equivalent to RDBMS. For that let us take Couchdatabase server for NoSQL and SQLServer for RDBMS

Couchdatabase ServerSQL ServerImportant notes on understanding similarities and also NoSQL concepts
ClusterServerThe cluster provides more scalability and high availability.
BucketDatabaseFor performance improvement, a built-in cache is provided by the bucket.
ScopeSchema“dbo” is the schema name in SQL Server but not always
CollectionTableMore flexibility is provided via collections. As there is no need to strongly provide the column definition and constraints, more flexibility is seen in NoSQL.
DocumentRowData is available in the format of JSON
N1QLTSQLThere is no strict rule like keeping constraints and table mapping. But still, it can able to provide similar support using N1QL which is sometimes called SQL++
Document KeyPrimary KeyDocument keys are unique to collection similar to Primary key
IndexIndexIndexes are created on JSON fields

Next, let us see the datatype difference between SQL Server database and Couch Database

SQL Server JSON data typeNarration
char, varchar, nvarchar, etcstringWhenever there is a need to specify alphanumeric data along with special characters, we can go for a string in JSON.
integer, decimal, float, real, etcnumberThere is no specific difference between integer and decimal but as a numeric pattern alone it is represented in JSON.
bitbooleanTo represent true/false
date, DateTime, time, etcstringIn a text pattern, alone date/time values are specified

While converting from SQL Server to Couch database or any other NoSQL database, the above-said terminologies need to be noted. Accordingly refactoring should be done and if required, redesigning the schema is also required.

The very main powerful advantage in any NoSQL database is data representation in the format of JSON. It is highly portable across the cloud and hence best suited for web and mobile applications. Nowadays all REST services are providing the response in JSON only. They are easily captured and stored in a NoSQL database by using simple collections/documents and in case if it has been placed in RDBMS, by using the above terminologies, redesigning needs to be done at a low cost and we get higher speed in the retrieval of data.

We have easier import tools available in each and every NoSQL database provided that we can able to transfer the data from any RDBMS in a JSON format. Hence JSON is the key way of communication between any RDBMS and NoSQL databases. To some extent XML also supports.

Conclusion:

Nowadays, moving to a NoSQL database is a better choice as in cloud architecture like AWS(Amazon Web Services) and Azure, NoSQL is the most used database. Hence strategically moving to NoSQL is the best choice.

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