Scan Table

In this step, we will scan all the data in the DynamoDB table.

1. Select the Schema tab

• Add the line below to the Query type to add a new query called allPost

    allPost(count: Int, nextToken: String): PaginatedPosts!

• Add the new PaginatedPosts type

type PaginatedPosts {
    posts: [Post!]!
    nextToken: String
}

• Then click Save Schema

2. Next, in the Resolvers pane on the right, find the allPost field of type Query, then select Attach

3. On the Attach resolver configuration page:

• Resolver type: Select Unit resolver
• Resolver runtime: Select Velocity Template Language (VTL)
• Data source name: Select PostDynamoDBTable
• Click the orange Create button.

4. On the code editor page of the newly created Resolver:

• Delete the default code and paste the content below into the Configure the request mapping template section:

{
    "version" : "2017-02-28",
    "operation" : "Scan"
    #if( ${context.arguments.count} )
        ,"limit": $util.toJson($context.arguments.count)
    #end
    #if( ${context.arguments.nextToken} )
        ,"nextToken": $util.toJson($context.arguments.nextToken)
    #end
}

• Scroll down, delete the default code, and paste the content below into the Configure the response mapping template section:

#if($context.error)
  $util.error($context.error.message, $context.error.type)
#end
{
    "posts": $utils.toJson($context.result.items)
    #if( ${context.result.nextToken} )
        ,"nextToken": $util.toJson($context.result.nextToken)
    #end
}

• Then click Save in the corner of the page to save

5. Select the Queries tab on the left menu

• Delete the default code, paste the script below into the Queries section to add some sample posts to the table:

mutation addPost {
  post1: addPost(id:"1" author: "AUTHORNAME" title: "A series of posts, Volume 1" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post2: addPost(id:"2" author: "AUTHORNAME" title: "A series of posts, Volume 2" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post3: addPost(id:"3" author: "AUTHORNAME" title: "A series of posts, Volume 3" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post4: addPost(id:"4" author: "AUTHORNAME" title: "A series of posts, Volume 4" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post5: addPost(id:"5" author: "AUTHORNAME" title: "A series of posts, Volume 5" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post6: addPost(id:"6" author: "AUTHORNAME" title: "A series of posts, Volume 6" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post7: addPost(id:"7" author: "AUTHORNAME" title: "A series of posts, Volume 7" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post8: addPost(id:"8" author: "AUTHORNAME" title: "A series of posts, Volume 8" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
  post9: addPost(id:"9" author: "AUTHORNAME" title: "A series of posts, Volume 9" content: "Some content" url: "https://aws.amazon.com/appsync/" ) { title }
}

query scanTable {
  allPost(count: 3) {
    posts {
      id
      title
      author
    }
    nextToken
  }
}

• Then click the Run button (the orange Play button), select addPost (if given the option) to run.

6. Now we will try to scan the table. Click the Run button (the orange Play button), select scanTable (if given the option). The result will return up to 3 posts along with a nextToken to fetch the next pages.

7. Copy the value of the returned nextToken field (this is a long string code).

8. Add the nextToken field to the allPost query command, then assign the string value you just copied to it:

query scanTable {
  allPost(count: 3, nextToken: "THE_VALUE_YOU_JUST_COPIED") {
    posts {
      id
      title
      author
    }
    nextToken
  }
}

9. Click the Run button (the orange Play button) again to see the next posts.

So you have scanned the entire table, returning your desired amount each time.