How to access nested elements in DynamoDB with NodeJS and Conditional Expresions?

Question

I'm having issues trying to access elements that are nested within a DynamoDB table using conditional expressions. The code I am trying is as follows:

const params = {
TableName: 'Games',
Key: {
  id: gameID.id,
},
UpdateExpression: 'SET #players = list_append(#answers , :answer)',
ConditionExpression: '#players CONTAINS :playerID',
ExpressionAttributeNames: {
  '#players': 'Players',
  '#answers': 'answers',
},
ExpressionAttributeValues: {
  ':playerID': userID.id,
  ':answer': tempAnswerList,
},
ReturnValues: 'ALL_NEW',

This version for example raises the error:

Invalid ConditionExpression: Syntax error; token: "CONTAINS", near: "#players CONTAINS :playerID"

Example DB Schema

Is there a way to look through an array without knowing it's id? Just as a note I have looked for wildcards to use on #players as it is a list but I cannot see one in the docs.

Thanks, Mark

notionquest · Accepted Answer · 2018-05-15 15:24:13Z

2

Please change the contains as mentioned below and try.

ConditionExpression: 'contains (#players, :playerID)',

edited May 15, 2018 at 15:24

answered May 15, 2018 at 15:19

notionquest

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6 Comments

Mark Addis Over a year ago

Thanks for that suggestion but now I get Invalid ConditionExpression: Invalid function name; function: CONTAINS

notionquest Over a year ago

function name is case sensitive. Please use lowercase. I have updated the answer.

Mark Addis Over a year ago

Thanks again, I think I've made progress. I'm not getting the usual error but this time got The conditional request failed. So hopefully this is to do with my logic now rather than the request. Out of interest do you know of anyway to search through nested items without a [].?

Mark Addis Over a year ago

Also, do you know how far contain searches through the object? As in will it look in any other child objects? I've gone over my CURL command and that should have returned one object so I'm a bit baffled.

notionquest Over a year ago

Contains basically requires the entire object to match the item in the array (i.e. all the attributes of the specific item in the array). It requires answers, player and score (all attributes) to match the item in the array.

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