Customize primary keys

Customize primary keys

By default, DataStore models have an id field that is automatically populated on the client with a UUID v4, allowing DataStore to generate non-colliding globally unique identifiers in a scalable way. While UUIDs have desirable properties (they are large, non-sequential and opaque), there are times when a custom primary key, also known as custom identifier, is needed. For instance, to:

• Have friendly/readable identifiers (surrogate/opaque vs. natural keys)
• Define composite primary keys
• Customize data partitioning to optimize for scale (especially important when planning to handle large amounts of data in short periods of time)
• Selectively synchronize data to clients (e.g. by fields like deviceId, userId or similar)
• Prioritize the sort order in which objects are returned by the sync queries
• Make existing data consumable and syncable by DataStore

A schema with the typical id field looks like this:

1type Book @model {
2  id: ID!
3  title: String!
4  description: String
5}

You can customize the primary key by adding the @primaryKey directive to a field:

1type Book @model {
2  isbn: ID! @primaryKey
3  title: String!
4  description: String
5}

You can also require multiple fields to define your primary key. When your primary key references multiple fields, it's called a composite key. In the example below, the primary key is defined by the isbn and title fields:

1type Book @model {
2  isbn: ID! @primaryKey(sortKeyFields: ["title"])
3  title: String!
4  description: String
5}

Determine when the primary key field is auto-populated upon record creation

When you create a record with DataStore, a UUID is automatically populated for the default id: ID! primary key field. When working with custom primary keys, DataStore will automatically populate the key fields in the following conditions:

1type Customer @model {
2  firstName: String
3  lastName: String
4}

1type Customer @model {
2  id: ID!
3  firstName: String
4  lastName: String
5}

1type Customer @model {
2  customerId: ID! @primaryKey
3  firstName: String
4  lastName: String
5}

1type Customer @model {
2  id: ID! @primaryKey
3  dob: AWSDateTime!
4  firstName: String
5  lastName: String
6}

1type Customer @model {
2  id: ID! @primaryKey(sortKeyFields: ["dob"])
3  dob: AWSDateTime!
4  firstName: String
5  lastName: String
6}

1type Customer @model {
2  country: String! @primaryKey(sortKeyFields: ["id"])
3  id: ID!
4  firstName: String
5  lastName: String
6}

1type Customer @model {
2  zip: String! @primaryKey(sortKeyFields: ["username"])
3  username: String!
4  firstName: String
5  lastName: String
6}

Querying records with custom primary keys

A record with a custom primary key can be queried for in the following ways:

With the value of the primary key:

1Amplify.DataStore.query(Book.self, byIdentifier: .identifier(isbn: "12345")) { result in
2    switch result {
3    case .success(let book):
4        guard let book = book else {
5            print("Query was successful with empty result")
6            return
7        }
8        print("Query was successful, retrieved book: \(book)")
9    case .failure(let error):
10        print("Error on query() for type Book with error: \(error)")
11    }
12}

With the value of QueryPredicate:

1Amplify.DataStore.query(Book.self, where: Book.keys.isbn == "12345") { result in
2    switch result {
3    case .success(let books):
4        print("Query was successful, retrieved books: \(books)")
5    case .failure(let error):
6        print("Error on query() for type Book with error: \(error)")
7    }
8}

Deleting records with custom primary keys

A record with a custom primary key can be deleted in the following ways:

With the value of the primary key:

1Amplify.DataStore.delete(Book.self, withIdentifier: .identifier(isbn: "12345")) { result in
2    switch result{
3    case .success:
4        print("Book deleted!")
5    case .failure(let error):
6        print("Error deleting book: \(error)")
7    }
8}

With the value of QueryPredicate:

1Amplify.DataStore.delete(Book.self, where: Book.keys.isbn == "12345") { result in
2    switch result {
3    case .success:
4        print("Book deleted!")
5    case .failure(let error):
6        print("Error deleting book: \(error)")
7    }
8}