Using Lambda with Nodejs Count Some queries in Dynamo DB

Question

After using the below to pull data from Dynamo db sucessfully

async function pullone(sessionid) {
  const params = {
    TableName: dynamodbTableName,
    Key: {
      'sessionid': sessionid
    }
  };
  return await dynamodb.get(params).promise().then((response) => {
    return response.Item
  }, (error) => {
    console.error('Do your custom error handling here. I am just gonna log it: ', error);
  });
}

Instead of 'return response.Item' i just want to return the count instead.

I tried doing count(pullone(sessionid)) but not sure if that is even a valid method. Please assist

Does this answer your question? https://stackoverflow.com/questions/27316643/how-to-get-item-count-from-dynamodb — BTL, Nov 24 '22 at 13:23

score 0 · Accepted Answer · answered Nov 24 '22 at 13:43

Not sure if I understood your question, but:

Since you're requesting data associated with a primary key, you'll get either 0 or 1 element in Item.

So, if you aim to know if "you've found something or not", you can use Number(response.Item != null) and you'll get 1 in case of "something" and 0 in case of "nothing".

If, instead, your data contains a "count" attribute, then (await pullone(sessionId)).count should work.

Otherwise, you have to query your DB (but you'll get Items (plural) in your response) and use the length() function of the Items array you'll get in the response.

the idea works. i.e one should just test for null. Thanks – faba Nov 24 '22 at 22:32 — faba, Nov 24 '22 at 22:32

Using Lambda with Nodejs Count Some queries in Dynamo DB

1 Answers1