AppSync batch insert to DynamoDB fails and returns null - amazon-dynamodb

Question

I have the following resolver settings:
#set($questions = [])
#foreach($item in ${ctx.args.questions})
#set($item.id = $util.dynamodb.toDynamoDBJson($util.autoId()))
$util.qr($questions.add($util.dynamodb.toMapValues($item)))
#end
{
"version" : "2018-05-29",
"operation" : "BatchPutItem",
"tables" : {
"QuestionTable": $utils.toJson($questions)
}
}
And the following GraphQL schema:
input CreateQuestionInput {
text: String
sectionId: ID!
}
input CreateScoreInput {
score: Int!
questionId: ID!
userId: ID!
}
input CreateSectionInput {
title: String
subSection: String
}
input DeleteQuestionInput {
id: ID!
}
input DeleteScoreInput {
id: ID!
}
input DeleteSectionInput {
id: ID!
}
type Mutation {
...
createQuestion(input: CreateQuestionInput!): Question
batchCreateQuestion(questions: [CreateQuestionInput]!): [Question]
}
type Query {
getSection(id: ID!): Section
listSections(filter: TableSectionFilterInput, limit: Int, nextToken: String): SectionConnection
getScore(id: ID!): Score
listScores(filter: TableScoreFilterInput, limit: Int, nextToken: String): ScoreConnection
getQuestion(id: ID!): Question
listQuestions(filter: TableQuestionFilterInput, limit: Int, nextToken: String): QuestionConnection
}
type Question {
id: ID!
text: String
sectionId: ID!
}
type QuestionConnection {
items: [Question]
nextToken: String
}
type Schema {
query: Query
}
type Score {
id: ID!
score: Int!
questionId: ID!
userId: ID!
}
type ScoreConnection {
items: [Score]
nextToken: String
}
type Section {
id: ID!
title: String
subSection: String
questions: [Question]
}
type SectionConnection {
items: [Section]
nextToken: String
}
input TableQuestionFilterInput {
id: TableIDFilterInput
text: TableStringFilterInput
sectionId: TableIDFilterInput
}
input UpdateQuestionInput {
id: ID!
text: String
sectionId: ID
}
(I've redacted some of the schema as it was fairly large).
When I attempt to run the query:
mutation BatchCreateQuestions($sec: ID!) {
batchCreateQuestion(questions: [
{
text: "Tester 1"
sectionId: $sec
},
{
text: "Tester 2",
sectionId: $sec
}
]) {
id
text
sectionId
}
}
With the variables:
{ "sec": "abc123" }
I get the response:
{
"data": {
"batchCreateQuestion": [
null,
null
]
}
}
And when I check the DynamoDB table, it hasn't saved the values. I've granted full dynamodb permissions for this datasource, but still no joy.

Answer 1

Turns out I'd given batch write permissions to a similarly named role instead of the role affecting this data source. If you see a similar issue, check your IAM roles/permissions. Silly me.

Answer 2

What does your response template look like in the resolver? It should be $util.toJson($ctx.result.data.QuestionTable) based on the above table name being QuestionTable as that gets automatically translated into the response context.