在适用于 .NET 的 AWS 开发工具包的 AsyncSearch 类中访问 DynamoDB 分页令牌时出现问题

Question

我目前正在深入研究适用于 .NET 的 DynamoDB AWS SDK，特别是修改

AsyncSearch<T>

类来执行表查询。目标是将分页合并到我的应用程序中，根据 AWS 文档，分页令牌驻留在底层搜索对象中。该对象可通过

AsyncSearch<T>

类的 DocumentSearch 属性访问，并通过 GetNextSetAsync() 方法进行设置，如本 documentation 中所示。

您可以在此处找到 AsyncSearch 类文档。

但是，有一个问题 - 我正在努力解决 DocumentSearch 属性是私有的这一事实，这使得直接访问分页标记变得很棘手。

这是我的代码的一瞥：

public interface IAsyncSearch<T>
{
    bool IsDone { get; }
    string PaginationToken { get; }
    Dictionary<string, AttributeValue> NextKey { get; }

    Task<List<T>> GetRemainingAsync(CancellationToken token = default);
    Task<List<T>> GetNextSetAsync(CancellationToken token = default);
}

public class CustomAsyncSearch<T> : IAsyncSearch<T>
{
    private readonly AsyncSearch<T> _search;

    public CustomAsyncSearch(AsyncSearch<T> search)
    {
        _search = search;
    }

    async Task<List<T>> IAsyncSearch<T>.GetRemainingAsync(CancellationToken token)
    {
        return await _search.GetRemainingAsync(token);
    }

    async Task<List<T>> IAsyncSearch<T>.GetNextSetAsync(CancellationToken token)
    {
        return await _search.GetNextSetAsync(token);
    }

    public bool IsDone => _search.IsDone;
    public string PaginationToken => _search.DocumentSearch.PaginationToken?.ToString();
    
    public Dictionary<string, AttributeValue> NextKey => _search.DocumentSearch.NextKey;
}

我想知道是否有一种正确的方法可以从 AsyncSearch 类获取分页标记，而无需调整其内部结构。有关访问分页令牌或确保使用

AsyncSearch

类正确实现分页的任何见解或建议都将非常有帮助。

编辑： 这是适用于 .NET 的 AWS 开发工具包中的 AsyncSearch 类基类

namespace Amazon.DynamoDBv2.DataModel;

// Summary:
//     A strongly-typed object for retrieving search results (Query or Scan) from DynamoDB.
//
//
// Type parameters:
//   T:
public class AsyncSearch<T>
{
    private Search DocumentSearch { get; set; }

    private DynamoDBContext SourceContext { get; set; }

    private DynamoDBFlatConfig Config { get; set; }

    //
    // Summary:
    //     Flag that, if true, indicates that the search is done
    public bool IsDone => DocumentSearch.IsDone;

    internal AsyncSearch(DynamoDBContext source, DynamoDBContext.ContextSearch contextSearch)
    {
        SourceContext = source;
        DocumentSearch = contextSearch.Search;
        Config = contextSearch.FlatConfig;
    }

    //
    // Summary:
    //     Initiates the asynchronous execution to get the next set of results from DynamoDB.
    //     If there are more items in the Scan/Query, PaginationToken will be set and can
    //     be consumed in a new Scan/Query operation to resume retrieving items from this
    //     point.
    //
    // Parameters:
    //   cancellationToken:
    //     Token which can be used to cancel the task.
    //
    // Returns:
    //     A Task that can be used to poll or wait for results, or both. Results will include
    //     the next set of result items from DynamoDB.
    public async Task<List<T>> GetNextSetAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        List<Document> documents = await DocumentSearch.GetNextSetHelperAsync(cancellationToken).ConfigureAwait(continueOnCapturedContext: false);
        return SourceContext.FromDocumentsHelper<T>(documents, Config).ToList();
    }

    //
    // Summary:
    //     Initiates the asynchronous execution to get all the remaining results from DynamoDB.
    //
    //
    // Parameters:
    //   cancellationToken:
    //     Token which can be used to cancel the task.
    //
    // Returns:
    //     A Task that can be used to poll or wait for results, or both. Results will include
    //     the remaining result items from DynamoDB.
    public async Task<List<T>> GetRemainingAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        List<Document> documents = await DocumentSearch.GetRemainingHelperAsync(cancellationToken).ConfigureAwait(continueOnCapturedContext: false);
        return SourceContext.FromDocumentsHelper<T>(documents, Config).ToList();
    }
}

Answer 1

尝试创建一个包装类。它应该继承自AsyncSearch。

public class CustomeAsyncSearch<T> : AsyncSearch<T>, IAsyncSearch<T>
{
   public CustomAsyncSearch(AsyncSearch<T> search) : base(search)
   {
   }
   public string GetPaginationToken()
   {
      return DocumentSearch.PaginationToken?.ToString();
   }
}

现在您可以在代码中使用“CustomAsyncSearch”类并调用“GetPaginationToken”函数来获取分页令牌。此方法提供了一个简洁的解决方案。

希望这有效。