Customize your data model

Amplify automatically creates Amazon DynamoDB database tables for GraphQL types annotated with the @model directive in your GraphQL schema. You can create relations between the data models via the @hasOne, @hasMany, @belongsTo, and @manyToMany directives.

Setup database tables

The following GraphQL schema automatically creates a database table for "Todo". @model will also automatically add an id field as a primary key to the database table. See Configure a primary key to learn how to customize the primary key.

type Todo @model {
  content: String
}

Upon amplify push or cdk deploy, Amplify deploys the Todo database table and a corresponding GraphQL API to perform create, read, update, delete, and list operations.

In addition, @model also adds the helper fields createdAt and updatedAt to your type. The values for those fields are read-only by clients unless explicitly overwritten. See Customize creation and update timestamps to learn more.

Try listing all the todos by executing the following query:

query QueryAllTodos {
  listTodos() {
    todos {
      items {
        id
        content
        createdAt
        updatedAt
      }
    }
  }
}

Configure a primary key

Every GraphQL type with the @model directive will automatically have an id field set as the primary key. You can override this behavior by marking another required field with the @primaryKey directive.

In the example below, todoId is the database's primary key and an id field will no longer be created automatically anymore by the @model directive.

type Todo @model {
  todoId: ID! @primaryKey
  content: String
}

Without any further configuration, you'll only be able to query for a Todo via an exact equality match of its primary key field. In the example above, this is the todoId field.

Note: After a primary key is configured and deployed, you can't change it without deleting and recreating your database table.

You can also specify "sort keys" to use a combination of different fields as a primary key. This also allows you to apply more advanced sorting and filtering conditions on the specified "sort key fields".

type Inventory @model {
  productID: ID! @primaryKey(sortKeyFields: ["warehouseID"])
  warehouseID: ID!
  InventoryAmount: Int!
}

The schema above will allow you to pass different conditions to query the correct inventory item:

query QueryInventoryByProductAndWarehouse($productID: ID!, $warehouseID: ID!) {
  getInventory(productID: $productID, warehouseID: $warehouseID) {
    productID
    warehouseID
    inventoryAmount
  }
}

Configure a secondary index

Amplify uses Amazon DynamoDB tables as the underlying data source for @model types. For key-value databases, it is critical to model your access patterns with "secondary indexes". Use the @index directive to configure a secondary index.

Amazon DynamoDB is a key-value and document database that delivers single-digit millisecond performance at any scale but making it work for your access patterns requires a bit of forethought. DynamoDB query operations may use at most two attributes to efficiently query data. The first query argument passed to a query (the hash key) must use strict equality and the second attribute (the sort key) may use gt, ge, lt, le, eq, beginsWith, and between. DynamoDB can effectively implement a wide variety of access patterns that are powerful enough for the majority of applications.

A secondary index consists of a "hash key" and, optionally, a "sort key". Use the "hash key" to perform strict equality and the "sort key" for greater than (gt), greater than or equal to (ge), less than (lt), less than or equal to (le), equals (eq), begins with, and between operations.

type Customer @model {
  id: ID!
  name: String!
  phoneNumber: String
  accountRepresentativeID: ID! @index
}

The example client query below allows you to query for "Customer" records based on their accountRepresentativeID:

query QueryCustomersForAccountRepresentative($accountRepresentativeID: ID!) {
  customersByAccountRepresentativeID(
    accountRepresentativeID: $accountRepresentativeID
  ) {
    customers {
      items {
        id
        name
        phoneNumber
      }
    }
  }
}

You can also overwrite the queryField or name to customize the GraphQL query name, or secondary index name respectively:

type Customer @model {
  id: ID!
  name: String!
  phoneNumber: String
  accountRepresentativeID: ID!
    @index(name: "byRepresentative", queryField: "customerByRepresentative")
}

query QueryCustomersForAccountRepresentative($representativeId: ID!) {
  customerByRepresentative(accountRepresentativeID: $representativeId) {
    customers {
      items {
        id
        name
        phoneNumber
      }
    }
  }
}

To optionally configure sort keys, provide the additional fields in the sortKeyFields parameter:

type Customer @model @auth(rules: [{ allow: public }]) {
  id: ID!
  name: String! @index(name: "byNameAndPhoneNumber", sortKeyFields: ["phoneNumber"], queryField: "customerByNameAndPhone")
  phoneNumber: String
  accountRepresentativeID: ID! @index

The example client query below allows you to query for "Customer" based on their name and filter based on phoneNumber:

query MyQuery {
  customerByNameAndPhone(phoneNumber: { beginsWith: "+1" }, name: "Rene") {
    items {
      id
      name
      phoneNumber
    }
  }
}

Advanced

Rename generated queries, mutations, and subscriptions

You can override the names of any @model-generated GraphQL queries, mutations, and subscriptions by supplying the desired name.

type Todo @model(queries: { get: "queryFor" }) {
  name: String!
  description: String
}

In the example above, you will be able to run a queryForTodo query to get a single Todo element.

Disable generated queries, mutations, and subscriptions

You can disable specific operations by assigning their value to null.

type Todo @model(queries: { get: null }, mutations: null, subscriptions: null) {
  name: String!
  description: String
}

The example above disables the getTodo query, all mutations, and all subscriptions while allowing the generation of other queries such as listTodo.

Creating a custom query

You can disable the get query and create a custom query that enables us to retrieve a single Todo model.

type Query {
  getMyTodo(id: ID!): Todo @function(name: "getmytodofunction-${env}")
}

The example above creates a custom query that utilizes the @function directive to call a Lambda function for this query.

For the type definitions of queries, mutations, and subscriptions, see Type Definitions of the @model Directive.

Customize creation and update timestamps

The @model directive automatically adds createdAt and updatedAt timestamps to each entity. The timestamp field names can be changed by passing timestamps attribute to the directive.

type Todo
  @model(timestamps: { createdAt: "createdOn", updatedAt: "updatedOn" }) {
  name: String!
  description: String
}

For example, the schema above will allow you to query for the following contents:

type Todo {
  id: ID!
  name: String!
  description: String
  createdOn: AWSDateTime!
  updatedOn: AWSDateTime!
}

Modify subscriptions (real-time updates) access level

By default, real-time updates are on for all @model types, which means customers receive real-time updates and authorization rules are applied during initial connection time. You can also turn off subscriptions for that model or make the real-time updates public, receivable by all subscribers.

type Todo
  @model(subscriptions: { level: off }) { # or level: public
  name: String!
  description: String
}

Create multiple relationships between two models

You need to explicitly specify the connection field names if relational directives are used to create two connections of the same type between the two models.

type Individual @model {
  id: ID!
  homeAddress: Address @hasOne
  shippingAddress: Address @hasOne
}

type Address @model {
  id: ID!
  homeIndividualID: ID
  shippingIndividualID: ID
  homeIndividual: Individual @belongsTo(fields: ["homeIndividualID"])
  shipIndividual: Individual @belongsTo(fields: ["shippingIndividualID"])
}

Relationships to a model with a composite primary key

When a primary key is defined by a sort key in addition to the hash key, then it's called a composite primary key.

If you explicitly define the fields argument on the @hasOne, @hasMany, or @belongsTo directives and reference a model that has a composite primary key, then you must set the values in the fields argument in a specific order:

• The first value should always be the primary key of the related model.
• Remaining values should match the sortKeyFields specified in the @primaryKey directive of the related model.

type Project @model {
  projectId: ID! @primaryKey(sortKeyFields: ["name"])
  name: String!
  team: Team @hasOne(fields: ["teamId", "teamName"])
  teamId: ID # customized foreign key for child primary key
  teamName: String # customized foreign key for child sort key
}

type Team @model {
  teamId: ID! @primaryKey(sortKeyFields: ["name"])
  name: String!
}

type Project @model {
  projectId: ID! @primaryKey(sortKeyFields: ["name"])
  name: String!
  team: Team @hasOne(fields: ["teamId", "teamName"])
  teamId: ID # customized foreign key for child primary key
  teamName: String # customized foreign key for child sort key
}

type Team @model {
  teamId: ID! @primaryKey(sortKeyFields: ["name"])
  name: String!
  project: Project @belongsTo(fields: ["projectId", "projectName"])
  projectId: ID # customized foreign key for parent primary key
  projectName: String # customized foreign key for parent sort key
}

type Post @model {
  postId: ID! @primaryKey(sortKeyFields: ["title"])
  title: String!
  comments: [Comment] @hasMany(indexName: "byPost", fields: ["postId", "title"])
}

type Comment @model {
  commentId: ID! @primaryKey(sortKeyFields: ["content"])
  content: String!
  postId: ID @index(name: "byPost", sortKeyFields: ["postTitle"]) # customized foreign key for parent primary key
  postTitle: String # customized foreign key for parent sort key
}

type Post @model {
  postId: ID! @primaryKey(sortKeyFields: ["title"])
  title: String!
  comments: [Comment] @hasMany(indexName: "byPost", fields: ["postId", "title"])
}

type Comment @model {
  commentId: ID! @primaryKey(sortKeyFields: ["content"])
  content: String!
  post: Post @belongsTo(fields: ["postId", "postTitle"])
  postId: ID @index(name: "byPost", sortKeyFields: ["postTitle"]) # customized foreign key for parent primary key
  postTitle: String # customized foreign key for parent sort key
}

Generate a secondary index without a GraphQL query

Because query creation against a secondary index is automatic, if you wish to define a secondary index that does not have a corresponding query in your API, set the queryField parameter to null.

type Customer @model {
  id: ID!
  name: String!
  phoneNumber: String
  accountRepresentativeID: ID! @index(queryField: null)
}

Split GraphQL files

AWS Amplify supports splitting your GraphQL schema into separate .graphql files.

You can start by creating a amplify/backend/api/<api-name>/schema/ directory. As an example, you might split up the schema for a blog site by creating Blog.graphql, Post.graphql, and Comment.graphql files.

You can then run amplify api gql-compile and the output build schema will include all the types declared across your schema files.

As your project grows, you may want to organize your custom queries, mutations, and subscriptions depending on the size and maintenance requirements of your project. You can either consolidate all of them into one file or colocate them with their corresponding models.

Using a Single Query.graphql File

This method involves consolidating all queries into a single Query.graphql file. It is useful for smaller projects or when you want to keep all queries in one place.

1. In the amplify/backend/api/<api-name>/schema/ directory, create a file named Query.graphql.

2. Copy all query type definitions from your multiple schema files into the Query.graphql file.

3. Make sure all your queries are properly formatted and enclosed within a single type Query { ... } block.

Using the extend Keyword

Declaring a Query type in separate schema files will result in schema validation errors similar to the following when running amplify api gql-compile:

🛑 Schema validation failed.

There can be only one type named "Query".

Amplify GraphQL schemas support the extend keyword, which allows you to extend types with additional fields. In this case, it also allows you to split your custom queries, mutations, and subscriptions into multiple files. This may be more ideal for larger, more complex projects.

1. Organize your GraphQL schema into multiple files as per your project's architecture.

2. In one of the files (e.g., schema1.graphql), declare your type normally:

type Query {
  # initial custom queries
}

3. In other schema files (e.g., schema2.graphql), use the extend keyword to add to the type:

extend type Query {
  # additional custom queries
}

How it works

Model directive

The @model directive will generate:

• An Amazon DynamoDB table with PAY_PER_REQUEST billing mode enabled by default.
• An AWS AppSync DataSource configured to access the table above.
• An AWS IAM role attached to the DataSource that allows AWS AppSync to call the above table on your behalf.
• Up to 8 resolvers (create, update, delete, get, list, onCreate, onUpdate, onDelete) but this is configurable via the queries, mutations, and subscriptions arguments on the @model directive.
• Input objects for create, update, and delete mutations.
• Filter input objects that allow you to filter objects in list queries and relationship fields.
• For list queries the default number of objects returned is 100. You can override this behavior by setting the limit argument.

Type definition of the @model directive

directive @model(
  queries: ModelQueryMap
  mutations: ModelMutationMap
  subscriptions: ModelSubscriptionMap
  timestamps: TimestampConfiguration
) on OBJECT

input ModelMutationMap {
  create: String
  update: String
  delete: String
}

input ModelQueryMap {
  get: String
  list: String
}

input ModelSubscriptionMap {
  onCreate: [String]
  onUpdate: [String]
  onDelete: [String]
  level: ModelSubscriptionLevel
}

enum ModelSubscriptionLevel {
  off
  public
  on
}

input TimestampConfiguration {
  createdAt: String
  updatedAt: String
}

Relational directives

The relational directives are @hasOne, @hasMany, @belongsTo and @manyToMany.

directive @hasOne(fields: [String!]) on FIELD_DEFINITION

directive @hasMany(
  indexName: String
  fields: [String!]
  limit: Int = 100
) on FIELD_DEFINITION

directive @belongsTo(fields: [String!]) on FIELD_DEFINITION

directive @manyToMany(
  relationName: String!
  limit: Int = 100
) on FIELD_DEFINITION