Relationships with AwsCdk, DynamoDB and AppSync - Typescript and lambda functions - graphql

Question

we are currently studying the stack: cdk, appsync and amplify to migrate our applications.
In our initial tests, we were able to upload a graphql api with only appsync wit relationships and it was very smooth, nice and fast.
When testing to build with cdk, we are having difficulties to create the relationships.
Here my code:
Schema
type Person {
id: ID!
name: String!
}
input PersonInput {
id: ID!
name: String!
}
input UpdatePersonInput {
id: ID!
name: String
}
type Client {
id: ID!
type: String!
personId: String
# Person: PersonConnection
Person: Person #connection(fields: ["personId"])
}
input ClientInput {
id: ID!
type: String!
personId: String!
}
input UpdateClientInput {
id: ID!
type: String
personId: String
}
My function
const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient();
async function list() {
const params = {
TableName: process.env.CLIENT_TABLE,
}
try {
const data = await docClient.scan(params).promise()
return data.Items
} catch (err) {
console.log('DynamoDB error: ', err)
return null
}
}
export default list;
My table
const clientTable = new dynamodb.Table(scope, 'ClientTable', {
billingMode: dynamodb.BillingMode.PAY_PER_REQUEST,
partitionKey: {
name: 'id',
type: dynamodb.AttributeType.STRING,
},
});
clientTable.addGlobalSecondaryIndex({
indexName: 'client-by-person-id',
partitionKey: {
name: 'personId',
type: dynamodb.AttributeType.STRING
},
sortKey: {
name: 'createdAt',
type: dynamodb.AttributeType.STRING
}
})
My query
query MyQuery {
listClients {
id
personId
type
Person {
name
}
}
}
However, my return to Person connection is null
"listClients": [
{
"id": "1",
"personId": "1",
"type": "PJ",
"Person": null
}
]
I would appreciate it if could point out our mistake

Answer 1

Solution of the problem based on the response of the Thorsten.
First, add resolver to the Person field in Client
export const clientResolvers = [{ typeName: "Client", fieldName: "Person" },...]
clientResolvers.map(((resolver: clientTypeResolver) => dataSource2.createResolver(resolver)))
Map function to the Person field in its lambda function
type AppSyncEvent = {
...
source: {personId: string,}
...
}
exports.handler = async (event:AppSyncEvent) => {
switch (event.info.fieldName) {
...
case "Person":
return await getPerson(event.source.personId);
}
}```
Function to solve the person field
async function getPerson(personId: string) {
console.log("CONTEXT\n" + JSON.stringify(personId, null, 2))
// console.log(context.source)
const params = {
TableName: process.env.PERSON_TABLE,
Key: { id: personId }
}
try {
const { Item } = await docClient.get(params).promise()
console.log("DATA\n" + JSON.stringify(Item, null, 2))
return Item
} catch (err) {
console.log('DynamoDB error: ', err)
}