[Fixed] Update part of attributes in DynamoDB

Serverless Framework
1

Use below codes, I successfully update an item

Then I add more attributes:

  const params = {
    TableName: process.env.DYNAMODB_TABLE,
    Key: {
      id: event.pathParameters.id,
    },
    ExpressionAttributeNames: {
      '#user_name': 'name',
    },
    ExpressionAttributeValues: {
      ':name': data.name,
      ':email': data.email,
      ':username': data.username,
      ':password': data.password,
      ':checked': data.checked,
      ':updatedAt': timestamp,
    },
    UpdateExpression: 'SET #user_name = :name, email = :email, username = :username, password = :password, checked = :checked, updatedAt = :updatedAt',
    ReturnValues: 'ALL_NEW',
  };

Above codes work fine if I feed all attributes.

$ cat test/user-1.json
{
  "name": "Bob",
  "email": "bob@example.com",
  "username": "bob",
  "password": "adfdsfdsf",
  "checked": false
}

But if I only want to update part of them, since I needn’t update email and password every time, I got error Couldn't fetch the user item.

$ cat test/user-1.json
{
  "name": "Bob",
  "username": "bob-1",
  "checked": false
}

$ curl -X PUT ${url}/${id} --data '@test/user-1.json'
Couldn't fetch the user item.

So how to change the code that I don’t have to update all attributes.

2

You need to look at data.email and data.password to see if they’re defined then dynamically generate the UpdateExpression and ExpressionAttributeValues so they only contain the values being updated.

1 Like
3

Thanks, @buggy. Looks this is the only solution.

I plan to get() from id first and compare with event.body, if email is in body key list, then I use it from event.body, otherwise, replace with exist email from get()

http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB/DocumentClient.html#get-property

4

Hi, I am using nodejs, is there any way to dynamically generate the ExpressionAttributeValues and the UpdateExpression for a nested json object like:
{
“id”: “12345”,
“sub”:{
“firstname”: “John”,
“lastname”: “Doe”,
“type”:{
“tyepid”: “7”,
“typename”: “ch”,
“otherole”: “other role”
},
“email”: “k.d@abc.com”
}}