Filter expression to check empty value is present in array or not in DynamoDB

Question

I have data stored as [ { "S": "" } ] in DynamoDB. I want to check whether the record contain empty value or not so I tried

FilterExpression : `contains (columnName, :data)`
   ExpressionAttributeValues:{
   ":data": ""
}

But i am getting no result from query. What is wrong with this?

Answer 1

I've created 2 items in the DDB table. 1 with empty value, 1 with non-empty value as follows:

Then I ran this query:

{
  "TableName": "xxx",
  "FilterExpression": "#DDB_data5vizmh5osmv = :data5vizmh5osmv",
  "ExpressionAttributeNames": {
    "#DDB_data5vizmh5osmv": "data"
  },
  "ExpressionAttributeValues": {
    ":data5vizmh5osmv": ""
  }
}

And here are the results I got. I filtered 1 item with empty value.