为什么在使用 Appsync 和 DynamoDB 时出现无效的 UpdateExpression： 语法错误？

Question

我是新的AppSync和DynamoDB，对不起，如果这个问题是基本的。我有这个模式的AppSync解析器:

type Profile {
name: String!
location: String!
}
input ProfileInput {
name: String!
location: String!
}
type Mutation {
createProfile(profileInput: ProfileInput!): Profile! @aws_cognito_user_pools @aws_api_key
}

解析器为:

{
"version" : "2017-02-28",
"operation" : "UpdateItem",
"key" : {
"name" : $util.dynamodb.toDynamoDBJson($ctx.identity.username),
"attribute": $util.dynamodb.toDynamoDBJson("info")
},
"update" : {
"expression" : "SET #p :da",
"expressionNames" : {
"#p" : "data"
},
"expressionValues" : {
":da" : $util.dynamodb.toDynamoDBJson($ctx.args.profileInput)
}
}
}

<<p>反应/strong>

$util.toJson($ctx.result)

我发送给Appsync的请求:

mutation CreateProfileMutation {
createProfile(profileInput: {location: "Updated Location", name: "Updated Username"}) {
location
name
}
}

但是Dynamodb抛出这个错误:

{
"data": null,
"errors": [
{
"path": [
"createProfile"
],
"data": null,
"errorType": "DynamoDB:DynamoDbException",
"errorInfo": null,
"locations": [
{
"line": 12,
"column": 3,
"sourceName": null
}
],
"message": "Invalid UpdateExpression: Syntax error; token: ":da", near: "#p :da" (Service: DynamoDb, Status Code: 400, Request ID: some id, Extended Request ID: null)"
}
]
}

转换后的模板为:

{
"version" : "2017-02-28",
"operation" : "UpdateItem",
"key" : {
"name" : {"S":"user#1"},
"attribute": {"S":"info"}
},
"update" : {
"expression" : "SET #p :da",
"expressionNames" : {
"#p" : "data"
},
"expressionValues" : {
":da" : {"M":{"name":{"S":"Updated Username"},"location":{"S":"Updated Location"}}}
}
}

}

它看起来像一个语法错误，但我不知道错误是什么。如有任何帮助，不胜感激。

Answer 1

更新表达式中的SET动作缺少=操作数。

应该是"expression" : "SET #p = :da"而不是"expression" : "SET #p :da"。