IReliableDictionary 上的 Linq 查询

Question

我查看和修改了很多代码，但还没有找到针对 IReliableDictionary 执行 Linq 查询的方法。我知道它与标准 IDictionary 不同，但我很好奇是否有人运气好。不幸的是，我开始认为这是不可能的。

Answer 1

如果您需要处理比简单 GetByKey() 更复杂的操作，您需要通过 IReliableDictionary.CreateEnumerable() method, which you would then be able to query similar to the following example from the comments in this discussion 显式创建它的本地集合：

IAsyncEnumerable<KeyValuePair<int, string="">> enumerable = await myDictionary.CreateEnumerableAsync(tx);
using (IAsyncEnumerator<KeyValuePair<int, string="">> e = enumerable.GetAsyncEnumerator())
{
    while (await e.MoveNextAsync(cancellationToken).ConfigureAwait(false))
    {
         doSomething(e.Current);
    }
}

这可能根本不适合您的情况，但它似乎是执行任何类型 "advanced queries" 的唯一方法。

Answer 2

目前，没有在可靠字典上执行 linq 查询的正常方法。话虽如此，您可以做一些事情。如前所述，CreateEnumerableAsync 方法存在的原因是因为服务结构将可靠字典分页到磁盘，但如果您知道底层集合很小并且您可以承受性能损失，那么以下 class 将起作用.

public static class AsyncEnumerableExtensions
{
    /// <summary>
    /// Converts the collection to a list
    /// </summary>
    /// <typeparam name="TValType">value type of the collection</typeparam>
    /// <param name="enumerator">enumerator to convert</param>
    /// <param name="ct">cancellation token for the async operations</param>
    /// <param name="tx">tx to enforce that this is called in a transactional context</param>
    /// <returns>a list containing all elements in the origin collection</returns>
    public static async Task<IList<TValType>> ToListAsync<TValType>(
        this IAsyncEnumerator<TValType> enumerator,CancellationToken ct, ITransaction tx)
    {
        IList<TValType> ret = new List<TValType>();
        while (await enumerator.MoveNextAsync(ct).ConfigureAwait(false))
        {
            ret.Add(enumerator.Current);
        }
        return ret;
    }

    /// <summary>
    /// Converts the collection to a list
    /// </summary>
    /// <typeparam name="TValType">value type of the collection</typeparam>
    /// <param name="enumerator">enumerator to convert</param>
    /// <param name="tx">tx to enforce that this is called in a transactional context</param>
    /// <returns>a list containing all elements in the origin collection</returns>
    public static Task<IList<TValType>> ToListAsync<TValType>(
        this IAsyncEnumerator<TValType> enumerator, ITransaction tx)
    {
        return enumerator.ToListAsync(CancellationToken.None,tx);
    }

    /// <summary>
    /// Converts the collection to a list
    /// </summary>
    /// <typeparam name="TValType">value type of the collection</typeparam>
    /// <param name="enumerable">enumerator to convert</param>
    /// <param name="ct">cancellation token for the async operations</param>
    /// <param name="tx">tx to enforce that this is called in a transactional context</param>
    /// <returns>a list containing all elements in the origin collection</returns>
    public static Task<IList<TValType>> ToListAsync<TValType>(this IAsyncEnumerable<TValType> enumerable,
        CancellationToken ct, ITransaction tx)
    {
        return enumerable.GetAsyncEnumerator().ToListAsync(ct,tx);
    }

    /// <summary>
    /// Converts the collection to a list
    /// </summary>
    /// <typeparam name="TValType">value type of the collection</typeparam>
    /// <param name="enumerable">enumerator to convert</param>
    /// <param name="tx">tx to enforce that this is called in a transactional context</param>
    /// <returns>a list containing all elements in the origin collection</returns>
    public static Task<IList<TValType>> ToListAsync<TValType>(this IAsyncEnumerable<TValType> enumerable, ITransaction tx)
    {
        return enumerable.GetAsyncEnumerator().ToListAsync(tx);
    }
}

您还可以实现自己的自定义枚举器和扩展方法，以高效方式对数据执行类似于 linq 查询的操作。我写了一些我想发布的，但他们首先需要一些润色。我有一种潜移默化的感觉，服务结构团队可能已经在处理它，但如果发生这种情况或何时发生，你的猜测和我的一样好。

Answer 3

正确的 LINQ 不能与 IAsyncEnumerator 一起工作

var wgEnumerable = await voteDictionary.CreateEnumerableAsync(tx);
using(IAsyncEnumerator<KeyValuePair<string, int>> enumerator = wgEnumerable.GetAsyncEnumerator())
{
while(await enumerator.MoveNextAsync(CancellationToken.None))
{
//Do something
}
}

Answer 4

看起来 MS 在最新的 SF 版本中删除了执行 linq 查询的功能。

Answer 5

将 SerivceFabric IAsyncEnumerable 转换为 dotnet 后，可以使用 Async Linq。

请参考这个回答： Convert IReliableDictionary to IList

IReliableDictionary 上的 Linq 查询

Linq query on IReliableDictionary

c#

linq

azure-service-fabric