Book Image

.Go Programming Blueprints - Second Edition

By : Mat Ryer
Book Image

.Go Programming Blueprints - Second Edition

By: Mat Ryer

Overview of this book

Go is the language of the Internet age, and the latest version of Go comes with major architectural changes. Implementation of the language, runtime, and libraries has changed significantly. The compiler and runtime are now written entirely in Go. The garbage collector is now concurrent and provides dramatically lower pause times by running in parallel with other Go routines when possible. This book will show you how to leverage all the latest features and much more. This book shows you how to build powerful systems and drops you into real-world situations. You will learn to develop high quality command-line tools that utilize the powerful shell capabilities and perform well using Go's in-built concurrency mechanisms. Scale, performance, and high availability lie at the heart of our projects, and the lessons learned throughout this book will arm you with everything you need to build world-class solutions. You will get a feel for app deployment using Docker and Google App Engine. Each project could form the basis of a start-up, which means they are directly applicable to modern software markets.
Table of Contents (13 chapters)

Querying in Google Cloud Datastore


So far, we have only been putting and getting single objects into and out of Google Cloud Datastore. When we display a list of answers to a question, we want to load all of these answers in a single operation, which we can do with datastore.Query.

The querying interface is a fluent API, where each method returns the same object or a modified object, allowing you to chain calls together. You can use it to build up a query consisting of ordering, limits, ancestors, filters, and so on. We will use it to write a function that will load all the answers for a given question, showing the most popular (those with a higher Score value) first.

Add the following function to answers.go:

func GetAnswers(ctx context.Context, questionKey *datastore.Key)  
([]*Answer, error) { 
  var answers []*Answer 
  answerKeys, err := datastore.NewQuery("Answer"). 
    Ancestor(questionKey). 
    Order("-Score"). 
    Order("-CTime"). 
    GetAll(ctx, &answers) 
  for i, answer ...