Query works at the console but not in code

Question

My DynamoDB table alexas has this item with key "abc" as seen in the DynamoDB console below:

However, the following query returns no result:

const params = { TableName: "alexas",
  KeyConditionExpression: "deviceId = :deviceId",
  ExpressionAttributeValues: { ":deviceId": "abc"}
}
const docClient = new AWS.DynamoDB.DocumentClient();
docClient.query(params, (err, data) => {
  if (err) {
    console.error(err);
  } else {
    console.log(data);
  }
});

The above code returns null for err and in data:

{ Items: [], Count: 0, ScannedCount: 0 }

I am new to the DynamoDB style of expressions. Is there anything wrong with my code which I took from here.

If instead of query, I used the scan method and just have TableName in params, I get the items in my table. This confirms that I am performing the operations on the correct table that has data.

score 4 · Accepted Answer · answered Jul 05 '19 at 11:24

The query returned no data because the key value does not match.

The item's deviceId is the string "abc" and not abc. Note the extra quotation marks.

The item was inserted using the DynamoDB console's Create editor and there is no need to include "" if the value is already expected to be of type string.

score 0 · Answer 2 · answered Jul 02 '19 at 13:21

0

DynamoDB's Scan operation doesn't take a KeyConditionExpression - only the Query operation takes this parameter. Scan always scans the entire table, and has a FilterExpression to post-filter these results (however please note that you still pay for scanning the entire table).

For example, here is the official documentation of Scan: https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_Scan.html

answered Jul 02 '19 at 13:21

Nadav Har'El

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You are right. I have changed the GUI to Query, and it's the same, with one row of result for `deviceId="abc"`. – Old Geezer Jul 03 '19 at 03:00

Ankit Deshpande · Answer 3 · 2019-07-05T08:45:40.550

0

Check QueryAPI

const params = { TableName: "alexas",
  KeyConditionExpression: "deviceId = :deviceId",
  ExpressionAttributeValues: {
     ":devideId":{
       S: "abc", // here
     }
  }
}
const docClient = new AWS.DynamoDB.DocumentClient();
docClient.query(params, (err, data) => {
  if (err) {
    console.error(err);
  } else {
    console.log(data);
  }
});

ExpressionAttributeValues needs to be passed in a different manner.

Update: Try using Exp attribute names, (I'm not sure if this will make a difference)

var params = {
     TableName: "alexas",
     KeyConditionExpression: "#d = :dId",
     ExpressionAttributeNames:{
          "#d": "email"
     },
     ExpressionAttributeValues: {
           ":dId": "abc"
     }
};

edited Jul 05 '19 at 08:45

answered Jul 04 '19 at 13:23

Ankit Deshpande

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With your method, I get `One or more parameter values were invalid: Condition parameter type does not match schema type`. My partition key is type string. – Old Geezer Jul 04 '19 at 15:23
Can you check the create table script or check data type of the device field ? – Ankit Deshpande Jul 04 '19 at 17:21
The Table Details say `Primary partition key: deviceId (String)` – Old Geezer Jul 05 '19 at 03:43
ok. try using exp attribute name with the query(updated the ans with it). If you have dynamodb local setup I'd suggest to debug the query on it. – Ankit Deshpande Jul 05 '19 at 08:46

Query works at the console but not in code

3 Answers3