How to delete an item in DynamoDB using Java?

Question

I know this sounds like a simple question, but for some reason I can't find a clear answer online or through StackOverflow.

I have a DynamoDB with a Table named "ABC". The primary key is "ID" as a String and one of the other attributes is "Name" as a String. How can I delete an item from this table using Java?

    AmazonDynamoDBClient dynamoDB;
    .
    .
    .
    DeleteItemRequest dir = new DeleteItemRequest();
    dir.withConditionExpression("ID = 214141").withTableName("ABC");
    DeleteItemResult deleteResult = dynamoDB.deleteItem(dir);

I have a validation exception:

Exception in thread "main" com.amazonaws.AmazonServiceException: 1 validation error detected: Value null at 'key' failed to satisfy constraint: Member must not be null (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException; Request ID: RQ70OIGOQAJ9MRGSUA0UIJLRUNVV4KQNSO5AEMVJF66Q9ASUAAJG)
    at com.amazonaws.http.AmazonHttpClient.handleErrorResponse(AmazonHttpClient.java:1160)
    at com.amazonaws.http.AmazonHttpClient.executeOneRequest(AmazonHttpClient.java:748)
    at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:467)
    at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:302)
    at com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient.invoke(AmazonDynamoDBClient.java:3240)
    at com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient.deleteItem(AmazonDynamoDBClient.java:972)
    at DynamoDBUploader.deleteItems(DynamoDBUploader.java:168)
    at Main.main(Main.java:56)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

---

If I need to know the Hash Key in order to delete an item in a DynamoDB Table, I think I may need to redesign my database in order to delete items efficiently.

My table looks like this: If that is the case, ahh... I think I need to re-design my database table.

ID | Name | Date | Value
-----------------------------------
1  | TransactionA | 2015-06-21 | 30
2  | TransactionB | 2015-06-21 | 40
3  | TransactionC | 2015-06-21 | 50

Basically, I would like to easily delete all transactions with Date "2015-06-21". How can I do this simply and quickly without having to deal with the Hash Key ID?

Answer 1

AWS DynamoDB knows the column that is hash key of your table. You just need to specify the value to be deleted. DeleteItemRequest has a fluent API for that :

Key keyToDelete = new Key().withHashKeyElement(new AttributeValue("214141"));
DeleteItemRequest dir = new DeleteItemRequest()
    .withTableName("ABC")
    .withKey(keyToDelete);

Answer 2

For Kotlin:

I have table with: Partition key: account_id (String) Sort key: message_id (String)

To delete an item fron DynamoDb I do the following:

    fun deleteMessageById(messageId: String, accountId: String){
        val item = HashMap<String, AttributeValue>()
        item["account_id"] = AttributeValue(accountId)
        item["message_id"] = AttributeValue(messageId)
        val deleteRequest = DeleteItemRequest().withTableName(tableName).withKey(item)
        dynamoConfiguration.amazonDynamoDB().deleteItem(deleteRequest)
    }