Lambda - Querying DynamoDB through Lambda

Question

I have a table called Customers with attributes CustId(partition Key), Fname, Lname, Dob.
I created a secondary index called LastNameIndex on Lname with the following params:

{
    TableName: 'Customers'
    AttributeDefinitions: [
        {
          AttributeName: 'Lname',
          AttributeType: 'S'
        }
    ],
    GlobalSecondaryIndexUpdates: [

        {
            Create: {
                IndexName: "LastNameIndex",
                KeySchema: [
                    {AttributeName: "Lname", KeyType: "HASH"}
                    
                ],
                Projection: {
                    "ProjectionType": "ALL"
                },
                ProvisionedThroughput: {                                
                    "ReadCapacityUnits": 1,"WriteCapacityUnits": 1
                }
            }
        }
    ]
}

Lambda function (snippet) - I want to get all records with Lname=Connors

params = {         
    TableName: "Customers",
    IndexName: "LastNameIndex",
    ExpressionAttributeNames: {
        "#FN": "Fname", 
        "#LN": "Lname",
        "#DB": "Dob",
        
    }, 
    ExpressionAttributeValues: {
        ":a": {
            S: "Connors"
        } 
    }, 
    KeyConditionExpression: "Lname = :a",
    ProjectionExpression: "#FN, #LN, #DB"
};

Running the query

ddb.query(params).promise().then(

    function(data) {
        console.log("Customer:" + data.Item)
        return data.Item;
    },
    function() {
        console.log("No records found...")
    }
);

I have a record with Lname = Connors.
But the query does not return me any records - any idea what's wrong with the params?

Could you try using ` ExpressionAttributeValues: { ":a": "Connors" },` ? — Ghamgui Khaled
– Ghamgui Khaled, Commented Oct 14, 2021 at 18:41
ExpressionAttributeValues: { ":a": "Connors" },` did not return any records — DavidC
– DavidC, Commented Oct 14, 2021 at 19:24
Console logging the returned data would help. Also, consider using the DocumentClient going forward as it has better support for native JS type inference and you can replace constructs such as ":a": {S: "Connors"} with ":a": "Connors". — jarmod
– jarmod, Commented Oct 14, 2021 at 23:41

Ahmad Nabil · Accepted Answer · 2021-10-14 23:28:43Z

1

The query operation returns multiple items not a single item like getItem operation. so I think returning data.Items instead of data.Item should work just fine.

ddb.query(params).promise().then(

    function(data) {
        console.log("Customer:" + data.Items)
        return data.Items;
    },
    function() {
        console.log("No records found...")
    }
);

answered Oct 14, 2021 at 23:28

Ahmad Nabil

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2 Comments

DavidC Over a year ago

I have accepted Ahmad Nabil's answer. I was thinking my params were wrong. However my params were correct, the way I was processing the results was wrong. Because it is a query it returns a array of records. I corrected my code as follows: ddb.query(params).promise().then( function(data) { console.log("Customer:" + data); data.Items.forEach(function(customer) { customer.Fname + ": " + customer.Lname + customer.Dob + "\n"; }); return data.Items; }, function() { console.log("No records found...") } );

Ahmad Nabil Over a year ago

As jarmod mentioned I would also recommend using documentClient instead because it's easier to work with. Also consider using aws sdk v3 for better performance than sdk v2.

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