Your Hash key (primary of sort) has to be unique (unless you have a range like stated by others).
In your case, to query your table you should have a secondary index.
| ID | DataID | Created | Data |
|------+--------+---------+------|
| hash | xxxxx | 1234567 | blah |
Your Hash Key is ID
Your secondary index is defined as: DataID-Created-index (that's the name that DynamoDB will use)
Then, you can make a query like this:
var params = {
TableName: "Table",
IndexName: "DataID-Created-index",
KeyConditionExpression: "DataID = :v_ID AND Created > :v_created",
ExpressionAttributeValues: {":v_ID": {S: "some_id"},
":v_created": {N: "timestamp"}
},
ProjectionExpression: "ID, DataID, Created, Data"
};
ddb.query(params, function(err, data) {
if (err)
console.log(err);
else {
data.Items.sort(function(a, b) {
return parseFloat(a.Created.N) - parseFloat(b.Created.N);
});
}
});
Essentially your query looks like:
SELECT * FROM TABLE WHERE DataID = "some_id" AND Created > timestamp;
The secondary Index will increase the read/write capacity units required so you need to consider that. It still is a lot better than doing a scan, which will be costly in reads and in time (and is limited to 100 items I believe).
This may not be the best way of doing it but for someone used to RD (I'm also used to SQL) it's the fastest way to get productive. Since there is no constraints in regards to schema, you can whip up something that works and once you have the bandwidth to work on the most efficient way, you can change things around.
