Merge pull request #4 from tonybka/feature/tonybka/update-document

Update document

README.md

@@ -6,10 +6,27 @@ Fundamental elements of DDD implementation in Golang microservice
 
 # Components
 ## Domain Layer
-- Entity
-- Value Object
-- Domain Event
+### Entity
+- Mutable, has identity
+### Value Object
+- Immutable, no identity
+### Domain Event
+- Utility for communication between bounded contexts, sub-domains, and between microservices
 
 ## Persistence Layer
 - Data Model
-- Repository
+- Repository
+
+
+# Q&A
+## Why UUIDv1 for entity's identity?
+### Reasons (short)
+- Need to have random, unique identity values for entities
+- To decouple domain layer from persistence layer, we should not use table row's id for entity's identity
+- MySQL support storing UUIDv1 as BINARY(16) in database which saves storage space
+
+### References
+- [Making UUIDs More Performant in MySQL](https://emmer.dev/blog/making-uuids-more-performant-in-mysql/)
+- [Storing UUID Values in MySQL Tables](https://dev.mysql.com/blog-archive/storing-uuid-values-in-mysql-tables/)
+- [GUID/UUID Performance Breakthrough](http://mysql.rjweb.org/doc.php/uuid)
+- [Storing UUID Values in MySQL](https://www.percona.com/blog/2014/12/19/store-uuid-optimized-way/)

samples/persistence/account/account_repository.go

@@ -14,13 +14,15 @@ func NewAccountRepository(db *gorm.DB) *AccountRepository {
 	return &AccountRepository{db}
 }
 
+// Create creates new account
 func (repo *AccountRepository) Create(dataModel AccountModel) error {
 	if result := repo.db.Create(&dataModel); result.Error != nil {
 		return result.Error
 	}
 	return nil
 }
 
+// FindById query account by it's identity
 func (repo *AccountRepository) FindById(id uuid.UUID) (AccountModel, error) {
 	var dataModel AccountModel
 
@@ -31,6 +33,7 @@ func (repo *AccountRepository) FindById(id uuid.UUID) (AccountModel, error) {
 	return dataModel, nil
 }
 
+// GetAll returns all accounts in the table
 func (repo *AccountRepository) GetAll() ([]AccountModel, error) {
 	var dataModels []AccountModel