Book Image

Haskell Cookbook

Book Image

Haskell Cookbook

Overview of this book

Haskell is a purely functional language that has the great ability to develop large and difficult, but easily maintainable software. Haskell Cookbook provides recipes that start by illustrating the principles of functional programming in Haskell, and then gradually build up your expertise in creating industrial-strength programs to accomplish any goal. The book covers topics such as Functors, Applicatives, Monads, and Transformers. You will learn various ways to handle state in your application and explore advanced topics such as Generalized Algebraic Data Types, higher kind types, existential types, and type families. The book will discuss the association of lenses with type classes such as Functor, Foldable, and Traversable to help you manage deep data structures. With the help of the wide selection of examples in this book, you will be able to upgrade your Haskell programming skills and develop scalable software idiomatically.
Table of Contents (13 chapters)

Managing migrations

When you are working on the databases, and trying to abstract the model on the backend at the same time, you already know that you will need a change in the model, database, or both at some point in time. Catering to changes in the requirements, performance criteria, database schema, or the data model on the backend is inevitable. Changing the database schema without breaking the backend becomes an important and time-consuming task.

In this recipe, we will look at migrations and see how Persistent approaches this issue. We will create a simple model and make a change to the model and run migrations again. We will be using SQLite as the backend.

How to do it...

  1. Create a new project called managing-migrations...