rmaziarka

This is an obvious reference to the There Is No Antimemetics Division book, but I couldn't resist it ;) (btw it is very good if you like semi-sf stories)

I want to highlight that in a usual bigger system (just bigger, not a really big one) there are no strict CRUD subdomains / components. There are obviously simpler ones which require less thinking, and complex ones. But there is no CRUD as simple Create / Read / Update / Delete. You will always need to apply some analysis and work around it.

Let's go through typical E-commerce domain to get the idea. For each CRUD word I will ask several question to show that answers are not that simple. Then you can adjust this mindset to your own domain.

Create

You could think that this case is a simple one - shouldn't you always be able to create something? You are almost right, but sometimes reality is tricky.

rmaziarka

let queryRUChargeData = AzureDiagnostics
| where Category == "DataPlaneRequests"
| where OperationName == "Query"
| project requestCharge_s, operationType_s, activityId_g, databaseName_s, collectionName_s, requestResourceType_s, requestResourceId_s, OperationName, TimeGenerated, callerId_s, clientIpAddress_s, userAgent_s;
AzureDiagnostics
| where Category == "QueryRuntimeStatistics"
| join queryRUChargeData on $left.activityId_g == $right.activityId_g
| summarize SumRU = sum(todouble(requestCharge_s1)), Count = count(requestCharge_s1) by collectionname_s

rmaziarka

// it was easier to describe this file on my blog that here:
// https://radekmaziarka.pl/2020/04/12/markdown-generation

'use strict';

const fs = require('fs');
const path = require('path');
const xml2js = require('xml2js');
const TurndownService = require('turndown');
var moment = require('moment');

rmaziarka

   public class ProductReadModel
    {
        public ProductReadModel(ProductAddedEvent @event)
        {
            Id = @event.Id;
            Name = @event.Name;
            CategoryId = @event.CategoryId;

            OrderAmount = 0;
            Review = new ReviewReadModel();

rmaziarka

    class Program
    {
        static async Task Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            try
            {
                await CreateTableAsync("tags");

rmaziarka

    public class Category
    {
        public int Id { get; set; }

        public string Name { get; set; }

        public List<Field> Fields { get; set; }
    }

rmaziarka

INSERT INTO ProductReadModel 
SELECT 
   P.[Id], 
   P.[Name], 
   P.[CategoryId], 
   ( 
      SELECT 
         COUNT(O.Id) 
      FROM 
         OrderItems AS O 

rmaziarka

    public class ProductAddedEventHandler: INotificationHandler<ProductAddedEvent>
    {
        private readonly IProductReadModelRepository _repo;

        public ProductAddedEventHandler(IProductReadModelRepository repo)
        {
            _repo = repo;
        }

        public void Handle(ProductAddedEvent @event)

rmaziarka

    public class ProductAddedEvent : INotification
    {
        public ProductAddedEvent(int id, string name, int categoryId)
        {
            Id = id;
            Name = name;
            CategoryId = categoryId;
        }

        public int Id { get; }

rmaziarka

    public class AddProductCommandHandler : IRequestHandler<AddProductCommand>
    {
        private readonly ProductDatabase _database;
        private readonly IMediator _mediator;

        public AddProductCommandHandler(ProductDatabase database, IMediator mediator)
        {
            _database = database;
            _mediator = mediator;
        }