Pagination with Filtering in DynamoDB Template

Schema:

type Query {
	getUserTwitterFeed(handle: String!): User
}

type Tweet {
	tweet_id: String!
	tweet: String!
	retweeted: Boolean!
	retweet_count: Int
	favorited: Boolean!
}

type TweetConnection {
	items: [Tweet]
	nextToken: String
}

type User {
	name: String!
	handle: String!
	location: String!
	description: String!
	followers_count: Int!
	friends_count: Int!
	favourites_count: Int!
	followers: [String]
	tweets(limit: Int, nextToken: String): TweetConnection
}

schema {
	query: Query
}

Request Mapping Template:

{
    "version": "2017-02-28",
    "operation": "Query",
    "query": {
        "expression": "handle = :handle",
        "expressionValues": {
            ":handle": {
                "S": "$context.source.handle"
            }
        }
    },    
    "limit": #if($context.arguments.limit) $context.arguments.limit #else 10 #end,
    "nextToken": #if($context.arguments.nextToken) "$context.arguments.nextToken" #else null #end
    #if(${context.arguments.keyword})
    ,"filter": {
        "expression": "contains (#tweet, :keyword)",
        "expressionNames" : {
          	"#tweet" : "tweet"
        },        
        "expressionValues": {
            ":keyword": { "S": "${context.arguments.keyword}" }
        }
      }
    #end   
}

Response Mapping Template:

{
    "items": $util.toJson($context.result.items),
    "nextToken": $util.toJson($context.result.nextToken)
}

Query:

I am trying to write a mapping template to paginate tweets with a given filter. My dynamodb table has simple structure: hash key = handle, sort key = tweet_id

When I don’t pass keyword parameter, everything runs fine. But now I added another condition to the mapping template i.e if the keyword is an input then filter tweets by keyword. But I see weird error in the above screenshot. Took reference to add Query Filters from here

Any idea what is happening? Thanks!

[mattiLeBlanc]

I find this whole dynamodb / appsync / filtering stuff unworkable. If you filter you can’t trust the nextToken for pagination, because you don’t know if the next page has results that might be filtered. The only way around it would be to have something in your sortkey that you can sort on so you group the records you want to keep after the filter and you can do some kind of predictive pagination.

We are really hitting limits with Appsync and Dynamo. Imagine having pagination in the middle of a 5 function pipeline resolver. You would have to run the whole pipeline 5 times 😃

[stock1232]

I am also interested in a solution for this. I would like to be able to filter a pagination result before the limit is taken into consideration