Update or delete every item a filter matches

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.UpdateMultiple.Basics;

// 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 Basic2_ByAFilter().RunAsync(dbContext);

The sample, as it is in the repository.

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

using static ArxSamples.DynamoDb.SampleOutput;

namespace ArxSamples.DynamoDb.Operations.UpdateMultiple.Basics;

/// <summary>
/// Every item a filter matches, changed or deleted in one call. DynamoDB reads by partition, so the filter gives one (a
/// customer's orders); ARX finds the items with one query, then writes each by its key in one transaction, conditioned on
/// the filter still matching it.
/// </summary>
/// <remarks>
/// <para>A filter that gives no partition key, of the table or an index, is refused (ARX8001): a write never scans. At most 100 items, the most one transaction can write.</para>
/// <para>The entity carries only the values to set: an id or a key attribute is refused (ARX1001).</para>
/// <para>Needs ARX.SDK 0.1.0-preview.5 or later.</para>
/// </remarks>
public sealed class Basic2_ByAFilter : ISample
{
    public string Name => "update-multiple-basics-2-by-a-filter";

    public string Title => "Update or delete every item a filter matches";

    public async Task RunAsync(SampleContext dbContext)
    {
        var orders = new List<ArxEntity>();

        for (var i = 1; i <= 4; i++)
        {
            var order = new ArxEntity("sales_order");
            order["customer_id"] = "C-DF01";
            order["order_number"] = $"SO-DF0{i}";
            order["status"] = "OPEN";
            order["ordered_on"] = "2026-11-11";
            order["total"] = i * 40m;
            orders.Add(order);
        }

        await dbContext.Service.CreateMultipleAsync(orders);

        await Scenario1_UpdateByAFilterAsync(dbContext.Service);

        await Scenario2_DeleteByAFilterAsync(dbContext.Service);
    }

    /// <summary>1. The customer's small orders cancelled: the GSI1 key moves with the status.</summary>
    private static async Task Scenario1_UpdateByAFilterAsync(ArxDynamoDbService service)
    {
        Step("1. Update by a filter");

        var change = new ArxEntity("sales_order");
        change["status"] = "CANCELLED";

        var filter = new ArxFilterExpression();
        filter.AddCondition("customer_id", ArxConditionOperator.Equal, "C-DF01");
        filter.AddCondition("total", ArxConditionOperator.LessThan, 100m);

        int changed = await service.UpdateMultipleAsync(change, filter);

        Show($"{changed} orders cancelled");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT "order_number", "status", "total", "GSI1PK" FROM "crm" WHERE "PK" = 'CUSTOMER#C-DF01' AND begins_with("SK", 'ORDER#')
         * -- Expect: 4 items; SO-DF01 and SO-DF02 (40, 80) CANCELLED with GSI1PK STATUS#CANCELLED, the other two OPEN.
         * ===========================================================
         */
    }

    /// <summary>2. The cancelled orders deleted by the same kind of filter; the call returns how many went.</summary>
    private static async Task Scenario2_DeleteByAFilterAsync(ArxDynamoDbService service)
    {
        Step("2. Delete by a filter");

        var filter = new ArxFilterExpression();
        filter.AddCondition("customer_id", ArxConditionOperator.Equal, "C-DF01");
        filter.AddCondition("status", ArxConditionOperator.Equal, "CANCELLED");

        int deleted = await service.DeleteMultipleAsync("sales_order", filter);

        Show($"{deleted} cancelled orders deleted");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT "order_number", "status" FROM "crm" WHERE "PK" = 'CUSTOMER#C-DF01' AND begins_with("SK", 'ORDER#')
         * -- Expect: 2 items, SO-DF03 and SO-DF04, both OPEN.
         * ===========================================================
         */
    }
}

  > 1. Update by a filter
      2 orders cancelled
  > 2. Delete by a filter
      2 cancelled orders deleted