Book Image

Learn Scala Programming

By : Slava Schmidt
Book Image

Learn Scala Programming

By: Slava Schmidt

Overview of this book

The second version of Scala has undergone multiple changes to support features and library implementations. Scala 2.13, with its main focus on modularizing the standard library and simplifying collections, brings with it a host of updates. Learn Scala Programming addresses both technical and architectural changes to the redesigned standard library and collections, along with covering in-depth type systems and first-level support for functions. You will discover how to leverage implicits as a primary mechanism for building type classes and look at different ways to test Scala code. You will also learn about abstract building blocks used in functional programming, giving you sufficient understanding to pick and use any existing functional programming library out there. In the concluding chapters, you will explore reactive programming by covering the Akka framework and reactive streams. By the end of this book, you will have built microservices and learned to implement them with the Scala and Lagom framework.
Table of Contents (19 chapters)

Chapter 14

  1. What is a database migration?

The database migration (or schema migration) is the automatic management of updates to the database schema. The changes to the schema are incremental, usually reversible, and applied in the moment the database schema needs to be changed in order to reflect changes in the application code.

  1. Describe what could be an alternative approach to discarding an order completely, in the case of insufficient stock for some articles?

One of the alternatives could be to satisfy orders for all articles for which there are sufficient stock. This could be implemented by running each inventory update in a separate transaction and combining the results of all of them that succeeded.

Yet another alternative would be to satisfy orders as fully as possible. This approach would require selecting rows for update, calculating new possible states, and applying...