I want to modify an existing java shopping cart app to make it work with a nosql database like Amazon Dynamo DB or Mongo DB… But the traditional MySQL db is a relational db- it has composite keys/primary/foreign keys– In contrast, in Amazon Dynamo DB there is either a single primary key, or a composite primary key comprised of 2 fields…
I have the detailed data model of the relational database…Now how do I go about converting it so that I have a database in Amazon Dynamo DB that is able to make the app work with Dynamo DB(i.e. no Sql database)? Are there any best practices/precautions that have to be kept in mind when doing this? Will this involve lot of work rewriting the application code as well? or can i handle all changes at database level itself, without modifying app’s logic?
Also, is there any tool that does most/large part of this work?
There is no automated way for this. NoSQL databases like MongoDB do not map data structures in the same way as MySQL. There are different performance characteristics and different ways how you can store data. In some cases you’d coalesce two SQL tables into one collection where you simply include the joined data in the same document.
How and when you’d do that, all depends on how you logically would group data, but just as much on the sort of workload you’re putting on your data. For example, for heavy reads and little writes, you might store the data differently than in the case where you have heavy writes and a few reads.
Besides having to redo the interface from your application to the database, you will also have to re-architecture your data model. That’s going to be as much work as designing your SQL structure and it works best not thinking of how you would do it in SQL. NoSQL vs SQL are two totally different beasts, which needs to be treated just as different!