# Amplify

* A managed serverless backend that is a layer onto of AppSync(Managed GraphQL API) and Lambda functions
* [17 Query patterns](https://docs.amplify.aws/cli-legacy/graphql-transformer/dataaccess/)

```bash
amplify push --iterative-rollback #to rollback the last-known-good state
amplify push --force #rollback the last-known-good state and try redeploying your changes again using.
```

## Modeling

Primitatives: ID | String | Int | Float | Boolean |

AWS Types: AWSDate | AWSTime | AWSDateTime | AWSTimestamp | AWSEmail | AWSJSON | AWSPhone | AWSURL | AWSIPAddress

```graphql
type Post @model {
  id: ID!
  title: String!
  comments: [Comment] @hasMany
}

type Comment @model {
  id: ID!
  content: String!
}
```

### Advanced Modeling

#### Adding Indexes

* The primary key of an index must use equality, the secondary/sort key can use gt, ge, lt, le, eq, beginsWith, and between
* Can have multiple sort keys and will created composite key, so you can query by more then three values
  * May need to backfill composite key
* `@index` is basically `@key` v2 and is used to define secondary index, while `@primaryKey` is for primary keys

```
type StoryLike @model @auth(rules: [{ allow: public }]) {
  userId: String! @primaryKey(sortKeyFields: ["storyId"])
  user: User @hasOne(fields: ["userId"])
  storyId: String!
  story: Story @hasOne(fields: ["storyId"])

  createdAt: String!
  updatedAt: String!
}
```

Will error out if the index primary or secondary key does not exist

```graphql
type Ranking @model @auth(rules: [{ allow: public }]) {
  id: String! @primaryKey

  type: String!
    @index(name: "ByTypeStatus", sortKeyFields: ["status"], queryField: "rankingByTypeStatus")
  userId: String!
    @index(name: "ByUserStatus", sortKeyFields: ["status"], queryField: "rankingByUserStatus")
  user: User @hasOne(fields: ["userId"])
  rank: Int! @default(value: "0")
  lastRank: Int
  status: String!

  createdAt: String!
  updatedAt: String!
}
```

## Using Javascript

#### [Query](https://docs.amplify.aws/lib/graphqlapi/query-data/q/platform/js/#simple-query)

```ts
import { API } from 'aws-amplify';
import { ThemesByEnabledQuery, Theme } from '../../API';
import { themesByEnabled } from '../../graphql/queries';

async function getEnabledThemes(): Promise<Theme[] | null> {
  console.log('getting enabled themes');

  try {
    const response = (await API.graphql({
      query: themesByEnabled,
      variables: {
        enabled: 1,
      },
    })) as { data: ThemesByEnabledQuery };

    const data = response.data.themesByEnabled;

    if (!data) {
      throw new Error('Data was null');
    }

    return data.items ?? null;
  } catch (err) {
    console.error('Failed to get enabled themes', err);
    return null;
  }
}

export default getEnabledThemes;

```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://openai.gitbook.io/code-cheatsheets/deployment/aws/amplify.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.