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

Example: Batch Operations Using AWS SDK for .NET Low-Level API

This section provides examples of batch operations, batch write and batch get, that DynamoDB supports.

Example: Batch Write Operation Using the AWS SDK for .NET Low-Level API

The following C# code example uses the BatchWriteItem method to perform the following put and delete operations:

  • Put one item in the Forum table

  • Put one item and delete one item from the Thread table.

You can specify any number of put and delete requests against one or more tables when creating your batch write request. However, DynamoDB BatchWriteItem limits the size of a batch write request and the number of put and delete operations in a single batch write operation. For more information, see BatchWriteItem. If your request exceeds these limits, your request is rejected. If your table does not have sufficient provisioned throughput to serve this request, the unprocessed request items are returned in the response.

The following example checks the response to see if it has any unprocessed request items. If it does, it loops back and resends the BatchWriteItem request with unprocessed items in the request. If you followed the steps in Creating Tables and Loading Sample Data, you already have the Forum and Thread tables created. You can also create these sample tables and upload sample data programmatically. For more information, see Creating Example Tables and Uploading Data Using the AWS SDK for .NET.

For step-by-step instructions to test the following sample, see .NET Code Samples.

using System;
using System.Collections.Generic;
using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.Model;
using Amazon.Runtime;

namespace com.amazonaws.codesamples
{
    class LowLevelBatchWrite
    {
        private static string table1Name = "Forum";
        private static string table2Name = "Thread";
        private static AmazonDynamoDBClient client = new AmazonDynamoDBClient();

        static void Main(string[] args)
        {
 
            try
            {
                TestBatchWrite();
            }
            catch (AmazonServiceException e) { Console.WriteLine(e.Message); }
            catch (Exception e) { Console.WriteLine(e.Message); }

            Console.WriteLine("To continue, press Enter");
            Console.ReadLine();
        }

        private static void TestBatchWrite()
        {
            var request = new BatchWriteItemRequest
            {
                ReturnConsumedCapacity = "TOTAL",
                RequestItems = new Dictionary<string, List<WriteRequest>>
         {
           {
             table1Name, new List<WriteRequest>
             {
               new WriteRequest
               {
                 PutRequest = new PutRequest
                 {
                   Item = new Dictionary<string, AttributeValue>
                   {
                     { "Name", new AttributeValue { S = "S3 forum" } },
                     { "Threads", new AttributeValue { N = "0" }}
                   }
                 }
               } 
             }
           },
           {
             table2Name, new List<WriteRequest>
             {
               new WriteRequest
               {
                 PutRequest = new PutRequest
                 {
                   Item = new Dictionary<string, AttributeValue>
                   {
                     { "ForumName", new AttributeValue { S = "S3 forum" } },
                     { "Subject", new AttributeValue { S = "My sample question" } },
                     { "Message", new AttributeValue { S = "Message Text." } },
                     { "KeywordTags", new AttributeValue { SS = new List<string> { "S3", "Bucket" }  } }
                   }
                 }
               },
               new WriteRequest
               {
                 // For the operation to delete an item, if you provide a primary key value 
                 // that does not exist in the table, there is no error, it is just a no-op.
                 DeleteRequest = new DeleteRequest
                 {
                   Key = new Dictionary<string, AttributeValue>()
                   {
                     { "ForumName",  new AttributeValue { S = "Some partition key value" } },
                     { "Subject", new AttributeValue { S = "Some sort key value" } }
                   }
                 }
               }
             }
           } 
         }
            };

            CallBatchWriteTillCompletion(request);
        }

        private static void CallBatchWriteTillCompletion(BatchWriteItemRequest request)
        {
            BatchWriteItemResponse response;

            int callCount = 0;
            do
            {
                Console.WriteLine("Making request");
                response = client.BatchWriteItem(request);
                callCount++;

                // Check the response.
                
                var tableConsumedCapacities = response.ConsumedCapacity;
                var unprocessed = response.UnprocessedItems;

                Console.WriteLine("Per-table consumed capacity");
                foreach (var tableConsumedCapacity in tableConsumedCapacities)
                {
                    Console.WriteLine("{0} - {1}", tableConsumedCapacity.TableName, tableConsumedCapacity.CapacityUnits);
                }

                Console.WriteLine("Unprocessed");
                foreach (var unp in unprocessed)
                {
                    Console.WriteLine("{0} - {1}", unp.Key, unp.Value.Count);
                }
                Console.WriteLine();

                // For the next iteration, the request will have unprocessed items.
                request.RequestItems = unprocessed;

            } while (response.UnprocessedItems.Count > 0);

            Console.WriteLine("Total # of batch write API calls made: {0}", callCount);
        }
    }
}

        

Example: Batch Get Operation Using the AWS SDK for .NET Low-Level API

The following C# code example uses the BatchGetItem method to retrieve multiple items from the Forum and the Thread tables. The BatchGetItemRequest specifies the table names and a list of primary keys for each table. The example processes the response by printing the items retrieved.

If you followed the steps in Creating Tables and Loading Sample Data, you already have these tables created with sample data. You can also create these sample tables and upload sample data programmatically. For more information, see Creating Example Tables and Uploading Data Using the AWS SDK for .NET.

For step-by-step instructions to test the following sample, see .NET Code Samples.

using System;
using System.Collections.Generic;
using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.Model;
using Amazon.Runtime;

namespace com.amazonaws.codesamples
{
    class LowLevelBatchGet
    {
        private static string table1Name = "Forum";
        private static string table2Name = "Thread";
        private static AmazonDynamoDBClient client = new AmazonDynamoDBClient();

        static void Main(string[] args)
        {
            try
            {
                RetrieveMultipleItemsBatchGet();

                Console.WriteLine("To continue, press Enter");
                Console.ReadLine();
            }
            catch (AmazonServiceException e) { Console.WriteLine(e.Message); }
            catch (Exception e) { Console.WriteLine(e.Message); }
        }

        private static void RetrieveMultipleItemsBatchGet()
        {
            var request = new BatchGetItemRequest
            {
                RequestItems = new Dictionary<string, KeysAndAttributes>()
        {
          { table1Name, 
            new KeysAndAttributes
            {
              Keys = new List<Dictionary<string, AttributeValue>>()
              {
                new Dictionary<string, AttributeValue>()
                { 
                  { "Name", new AttributeValue { S = "Amazon DynamoDB" } } 
                },
                new Dictionary<string, AttributeValue>()
                { 
                  { "Name", new AttributeValue { S = "Amazon S3" } } 
                }
              }
            }
          },
          {
            table2Name,
            new KeysAndAttributes
            {
              Keys = new List<Dictionary<string, AttributeValue>>()
              {
                new Dictionary<string, AttributeValue>()
                {
                  { "ForumName", new AttributeValue { S = "Amazon DynamoDB" } },
                  { "Subject", new AttributeValue { S = "DynamoDB Thread 1" } }
                },
                new Dictionary<string, AttributeValue>()
                {
                  { "ForumName", new AttributeValue { S = "Amazon DynamoDB" } },
                  { "Subject", new AttributeValue { S = "DynamoDB Thread 2" } }
                },
                new Dictionary<string, AttributeValue>()
                {
                  { "ForumName", new AttributeValue { S = "Amazon S3" } },
                  { "Subject", new AttributeValue { S = "S3 Thread 1" } }
                }
              }
            }
         }
       }
            };

            BatchGetItemResponse response;
            do
            {
                Console.WriteLine("Making request");
                response = client.BatchGetItem(request);

                // Check the response.
                var responses = response.Responses; // Attribute list in the response.

                foreach (var tableResponse in responses)
                {
                    var tableResults = tableResponse.Value;
                    Console.WriteLine("Items retrieved from table {0}", tableResponse.Key);
                    foreach (var item1 in tableResults)
                    {
                        PrintItem(item1);
                    }
                }

                // Any unprocessed keys? could happen if you exceed ProvisionedThroughput or some other error.
                Dictionary<string, KeysAndAttributes> unprocessedKeys = response.UnprocessedKeys;
                foreach (var unprocessedTableKeys in unprocessedKeys)
                {
                    // Print table name.
                    Console.WriteLine(unprocessedTableKeys.Key);
                    // Print unprocessed primary keys.
                    foreach (var key in unprocessedTableKeys.Value.Keys)
                    {
                        PrintItem(key);
                    }
                }

                request.RequestItems = unprocessedKeys;
            } while (response.UnprocessedKeys.Count > 0);
        }

        private static void PrintItem(Dictionary<string, AttributeValue> attributeList)
        {
            foreach (KeyValuePair<string, AttributeValue> kvp in attributeList)
            {
                string attributeName = kvp.Key;
                AttributeValue value = kvp.Value;

                Console.WriteLine(
                    attributeName + " " +
                    (value.S == null ? "" : "S=[" + value.S + "]") +
                    (value.N == null ? "" : "N=[" + value.N + "]") +
                    (value.SS == null ? "" : "SS=[" + string.Join(",", value.SS.ToArray()) + "]") +
                    (value.NS == null ? "" : "NS=[" + string.Join(",", value.NS.ToArray()) + "]")
                );
            }
            Console.WriteLine("************************************************");
        }
    }
}