AWS.DynamoDB: KeyConditionExpression is missing - amazon-web-services

Question

I wanted to make a search in DynamoDB equivalent to the following SQL query:
SELECT *
from db
where attr="abc"
Therefore, I wrote the following code:
function searchFile(carModel, busMapping, from_date, until_date, location, attackTraffic, isTagged) {
AWS.config = new AWS.Config({accessKeyId: '***', secretAccessKey: '***', region: 'us-west-2'});
var dynamodb = new AWS.DynamoDB({apiVersion: '2012-08-10'});
var params = {
"TableName" : 'db',
QueryFilter: {
"attr": {
ComparisonOperator: 'EQ',
AttributeValueList: [
{S: 'abc'}
]
}
}
}
dynamodb.query(params, function(err,data) {
if (err) {
alert(err);
}
})
}
I got the error message:
"Expected params.KeyConditionExpression to be a string"
I looked at the AWS documentation (http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/DynamoDB.html#query-property) and saw that params.KeyConditionExpression must be defined. However, I still didn't understand what is expected to be inside this key. Can you propose something that can make my query work?

Answer 1

To perform a query against DynamoDB you must provide it with the primary/hash/partition key for the table.
KeyConditionExpression: The condition must perform an equality test on a single partition key value. The partition key equality test is required, and must be specified in the following format: partitionKeyName = :partitionkeyval
What you probably want is to use the scan method and provide it with a ScanFilter instead of a QueryFilter:
function searchFile(carModel, busMapping, from_date, until_date, location, attackTraffic, isTagged) {
AWS.config = new AWS.Config({accessKeyId: '***', secretAccessKey: '***', region: 'us-west-2'});
var dynamodb = new AWS.DynamoDB({apiVersion: '2012-08-10'});
var params = {
TableName : 'db',
ScanFilter: {
attr: {
ComparisonOperator: 'EQ',
AttributeValueList: [
{S: 'abc'}
]
}
}
}
dynamodb.scan(params, function(err,data) {
if (err) {
alert(err);
}
})
}