A customer and its orders in one request

Runs the sample. Generated for this page; it reads the connection string from the environment and first remakes the sample database from sample-schema.json.

using ArxSamples.DynamoDb;
using ArxSamples.DynamoDb.Operations.RetrieveMultiple.RealCases;

// The connection string comes from the environment, never from the code (see "Configure the connection").
var connectionString = Environment.GetEnvironmentVariable("ARX_SAMPLES_DYNAMODB")
    ?? throw new InvalidOperationException("Set the ARX_SAMPLES_DYNAMODB environment variable to your Amazon DynamoDB connection string.");

var dbContext = new SampleContext(connectionString);

// Every run starts from the sample data: this deletes and makes again what sample-schema.json lists
// (save the file in the project folder, see Get started).
await dbContext.Direct.ResetAsync();

await new RealCase1_ACustomerAndItsOrders().RunAsync(dbContext);

The sample, as it is in the repository.

using ARX.SDK.DynamoDb.Services;
using ARX.SDK.Query;
using ARX.SDK.Services;

using static ArxSamples.DynamoDb.SampleOutput;

namespace ArxSamples.DynamoDb.Operations.RetrieveMultiple.RealCases;

/// <summary>
/// The single-table design's reason to exist: a customer and its orders in one request, in two scenarios: the whole
/// item collection, and a page of it.
/// </summary>
/// <remarks>
/// <c>QueryPartitionAsync</c> reads every item of the partition a key gives, whatever its entity, and returns each as the
/// entity its <c>entity_type</c> names, in sort key order: here the orders (<c>ORDER#…</c>) and then the profile
/// (<c>PROFILE</c>). A relational database would join two tables; DynamoDB stores them together so it needn't.
/// </remarks>
public sealed class RealCase1_ACustomerAndItsOrders : ISample
{
    public string Name => "retrieve-multiple-real-1-a-customer-and-its-orders";

    public string Title => "A customer and its orders in one request";

    public async Task RunAsync(SampleContext dbContext)
    {
        var customer = new ArxEntity("customer");
        customer["customer_id"] = "C-D431";
        customer["name"] = "Adventure Works Cycles";
        var batch = new List<ArxEntity> { customer };

        for (int i = 1; i <= 4; i++)
        {
            var order = new ArxEntity("sales_order");
            order["customer_id"] = "C-D431";
            order["order_number"] = $"SO-D43{i}";
            order["status"] = "OPEN";
            order["ordered_on"] = $"2026-10-2{i}";
            order["total"] = 100m * i;
            batch.Add(order);
        }

        await dbContext.Service.CreateMultipleAsync(batch);

        await Scenario1_TheWholeCollectionAsync(dbContext.Service);

        await Scenario2_APageOfItAsync(dbContext.Service);
    }

    /// <summary>1. The customer's partition: four orders and the profile, each its own entity.</summary>
    private static async Task Scenario1_TheWholeCollectionAsync(ArxDynamoDbService service)
    {
        Step("1. The whole collection");

        var key = new ArxEntity("customer");
        key["customer_id"] = "C-D431";

        var items = await service.QueryPartitionAsync(key);

        var profile = items.Entities.Single(x => x.EntityName == "customer");
        var orders = items.Entities.Where(x => x.EntityName == "sales_order").ToList();
        Show($"{profile["name"]}: {orders.Count} orders, {orders.Sum(x => (decimal)x["total"]!)} in all");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT "SK", "entity_type" FROM "crm" WHERE "PK" = 'CUSTOMER#C-D431'
         * -- Expect: 5 items: ORDER#SO-D431 to ORDER#SO-D434 (sales_order) and PROFILE (customer).
         * ===========================================================
         */
    }

    /// <summary>2. Two items at a time, with the cookie.</summary>
    private static async Task Scenario2_APageOfItAsync(ArxDynamoDbService service)
    {
        Step("2. A page of it");

        var key = new ArxEntity("customer");
        key["customer_id"] = "C-D431";

        var pages = 0;
        string? cookie = null;

        do
        {
            var page = await service.QueryPartitionAsync(key, new ArxPagingInfo { Count = 2, PagingCookie = cookie });
            pages++;
            cookie = page.PagingCookie;
        }
        while (cookie != null);

        Show($"read in {pages} pages");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT "SK" FROM "crm" WHERE "PK" = 'CUSTOMER#C-D431'
         * -- Expect: 5 items.
         * ===========================================================
         */
    }
}

  > 1. The whole collection
      Adventure Works Cycles: 4 orders, 1000 in all
  > 2. A page of it
      read in 3 pages