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Amazon DynamoDB
Developer Guide (API Version 2012-08-10)

Batch Operations Using AWS SDK for .NET Object Persistence Model

Batch Write: Putting and Deleting Multiple Items

To put or delete multiple objects from a table in a single request, do the following:

  • Execute CreateBatchWrite method of the DynamoDBContext and create an instance of the BatchWrite class.

  • Specify the items you want to put or delete.

    • To put one or more items, use either the AddPutItem or the AddPutItems method.

    • To delete one or more items, you can either specify the primary key of the item or a client-side object that maps to the item you want to delete. Use the AddDeleteItem, AddDeleteItems, and the AddDeleteKey methods to specify the list of items to delete.

  • Call the BatchWrite.Execute method to put and delete all the specified items from the table.

Note

When using object persistence model, you can specify any number of operations in a batch. However, note that DynamoDB limits the number of operations in a batch and the total size of the batch in a batch operation. For more information about the specific limits, see BatchWriteItem. If the API detects your batch write request exceeded the allowed number of write requests or exceeded the maximum allowed HTTP payload size, it breaks the batch in to several smaller batches. Additionally, if a response to a batch write returns unprocessed items, the API will automatically send another batch request with those unprocessed items.

Suppose that you have defined a C# class Book class that maps to the ProductCatalog table in DynamoDB. The following C# code snippet uses the BatchWrite object to upload two items and delete one item from the ProductCatalog table.

DynamoDBContext context = new DynamoDBContext(client);
var bookBatch = context.CreateBatchWrite<Book>();

// 1. Specify two books to add.
Book book1 = new Book
{
  Id = 902,
  ISBN = "902-11-11-1111",
  ProductCategory = "Book",
  Title = "My book3 in batch write"
};
Book book2 = new Book
{
  Id = 903,
  ISBN = "903-11-11-1111",
  ProductCategory = "Book",
  Title = "My book4 in batch write"
};


bookBatch.AddPutItems(new List<Book> { book1, book2 });

// 2. Specify one book to delete.
bookBatch.AddDeleteKey(111);

bookBatch.Execute();

To put or delete objects from multiple tables, do the following:

  • Create one instance of the BatchWrite class for each type and specify the items you want to put or delete as described in the preceding section.

  • Create an instance of MultiTableBatchWrite using one of the following methods:

    • Execute the Combine method on one of the BatchWrite objects that you created in the preceding step.

    • Create an instance of the MultiTableBatchWrite type by providing a list of BatchWrite objects.

    • Execute the CreateMultiTableBatchWrite method of DynamoDBContext and pass in your list of BatchWrite objects.

  • Call the Execute method of MultiTableBatchWrite, which performs the specified put and delete operations on various tables.

Suppose that you have defined Forum and Thread C# classes that map to the Forum and Thread tables in DynamoDB. Also, suppose that the Thread class has versioning enabled. Because versioning is not supported when using batch operations, you must explicitly disable versioning as shown in the following C# code snippet. The code snippet uses the MultiTableBatchWrite object to perform a multi-table update.

DynamoDBContext context = new DynamoDBContext(client);
// Create BatchWrite objects for each of the Forum and Thread classes.
var forumBatch = context.CreateBatchWrite<Forum>();

DynamoDBOperationConfig config = new DynamoDBOperationConfig();
config.SkipVersionCheck = true;
var threadBatch = context.CreateBatchWrite<Thread>(config);

// 1. New Forum item.
Forum newForum = new Forum
{
  Name = "Test BatchWrite Forum",
  Threads = 0
};
forumBatch.AddPutItem(newForum);

// 2. Specify a forum to delete by specifying its primary key.
forumBatch.AddDeleteKey("Some forum");

// 3. New Thread item.
Thread newThread = new Thread
{
  ForumName = "Amazon S3 forum",
  Subject = "My sample question",
  KeywordTags = new List<string> { "Amazon S3", "Bucket" },
   Message = "Message text"
};

threadBatch.AddPutItem(newThread);

// Now execute multi-table batch write.
var superBatch = new MultiTableBatchWrite(forumBatch, threadBatch);
superBatch.Execute();

For a working example, see Example: Batch Write Operation Using the AWS SDK for .NET Object Persistence Model.

Note

DynamoDB batch API limits the number of writes in batch and also limits the size of the batch. For more information, see BatchWriteItem. When using the .NET object persistence model API, you can specify any number of operations. However, if either the number of operations in a batch or size exceed the limit, the .NET API breaks the batch write request into smaller batches and sends multiple batch write requests to DynamoDB.

Batch Get: Getting Multiple Items

To retrieve multiple items from a table in a single request, do the following:

  • Create an instance of the CreateBatchGet class.

  • Specify a list of primary keys to retrieve.

  • Call the Execute method. The response returns the items in the Results property.

The following C# code sample retrieves three items from the ProductCatalog table. The items in the result are not necessarily in the same order in which you specified the primary keys.

DynamoDBContext context = new DynamoDBContext(client);
var bookBatch = context.CreateBatchGet<ProductCatalog>();
bookBatch.AddKey(101);
bookBatch.AddKey(102);
bookBatch.AddKey(103);
bookBatch.Execute();
// Process result.
Console.WriteLine(devBatch.Results.Count);
Book book1 = bookBatch.Results[0];
Book book2 = bookBatch.Results[1];
Book book3 = bookBatch.Results[2];

To retrieve objects from multiple tables, do the following:

  • For each type, create an instance of the CreateBatchGet type and provide the primary key values you want to retrieve from each table.

  • Create an instance of the MultiTableBatchGet class using one of the following methods:

    • Execute the Combine method on one of the BatchGet objects you created in the preceding step.

    • Create an instance of the MultiBatchGet type by providing a list of BatchGet objects.

    • Execute the CreateMultiTableBatchGet method of DynamoDBContext and pass in your list of BatchGet objects.

  • Call the Execute method of MultiTableBatchGet which returns the typed results in the individual BatchGet objects.

The following C# code snippet retrieves multiple items from the Order and OrderDetail tables using the CreateBatchGet method.

var orderBatch = context.CreateBatchGet<Order>();
orderBatch.AddKey(101);
orderBatch.AddKey(102);
 
var orderDetailBatch = context.CreateBatchGet<OrderDetail>();
orderDetailBatch.AddKey(101, "P1");
orderDetailBatch.AddKey(101, "P2");
orderDetailBatch.AddKey(102, "P3");
orderDetailBatch.AddKey(102, "P1");
 
var orderAndDetailSuperBatch = orderBatch.Combine(orderDetailBatch);
orderAndDetailSuperBatch.Execute();
 
Console.WriteLine(orderBatch.Results.Count);
Console.WriteLine(orderDetailBatch.Results.Count);
 
Order order1 = orderBatch.Results[0];
Order order2 = orderDetailBatch.Results[1];
OrderDetail orderDetail1 = orderDetailBatch.Results[0];