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:

type Book @model {
  id: ID!
  title: String!
  description: String
}

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

type Book @model {
  isbn: ID! @primaryKey
  title: String!
  description: String
}

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:

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

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:

type Customer @model {
  firstName: String
  lastName: String
}

type Customer @model {
  id: ID!
  firstName: String
  lastName: String
}

type Customer @model {
  customerId: ID! @primaryKey
  firstName: String
  lastName: String
}

type Customer @model {
  id: ID! @primaryKey
  dob: AWSDateTime!
  firstName: String
  lastName: String
}

type Customer @model {
  id: ID! @primaryKey(sortKeyFields: ["dob"])
  dob: AWSDateTime!
  firstName: String
  lastName: String
}

type Customer @model {
  country: String! @primaryKey(sortKeyFields: ["id"])
  id: ID!
  firstName: String
  lastName: String
}

type Customer @model {
  zip: String! @primaryKey(sortKeyFields: ["username"])
  username: String!
  firstName: String
  lastName: String
}

Querying records with custom primary keys

In addition to querying by the model type (or Predicates.ALL), a record with a custom primary key can be queried several ways.

With the value of the primary key:

const book = await DataStore.query(Book, '12345');

With a predicate:

const books = await DataStore.query(Book, b =>
    t.isbn.eq('12345')
);

const books = await DataStore.query(Book, b => b.and(
    b => [
        b.isbn.eq('12345'),
        b.title.eq('My Book')
    ])
);

With an object literal:

const book = await DataStore.query(Book, { 
    isbn: '12345' 
});

// Both keys are required for composite keys
const book = await DataStore.query(Book, {
    isbn: '12345',
    title: 'My Book',
});

Deleting records with custom primary keys

In addition to deleting by the model type (or Predicates.ALL), a record with a custom primary key can be deleted the following ways:

With the value of the primary key:

const book = await DataStore.delete(Book, '12345');

With a predicate:

const book = await DataStore.delete(Book, b =>
    b.isbn.eq('12345')
);

const book = await DataStore.delete(Book, b => b.and([
    b.isbn.eq('12345'),
    b.title.eq('My Book')
]));

With an object literal:

const book = await DataStore.delete(Book, { 
    isbn: '12345' 
});

const book = await DataStore.delete(Book, {
    isbn: '12345',
    title: 'My Book',
});