如果數組屬性包含給定列表中的任何項目，如何查詢 Cosmos DB？

Question

如果你有一個像這樣的實體 class 存儲在你的 cosmos 數據庫中

public class SomeItem
{
    public Guid Id { get; set; }
    public IReadOnlyList<string> AffectedUsers { get; set; }
}

在您的代碼中，您會收到一個用戶列表，並且您必須查詢列出其中任何一個的所有項目：

var cosmosClient = new CosmosClient("https://test.local/", "Tm9LZXk=");
var container = cosmosClient.GetContainer("123", "456");

// A list of users where we like to get all items, where any of them is listed in affected users.
var someUsers = Enumerable.Range(1, 5).Select(i => $"User {i}").ToList();

// The query that should check if any user of the above list is within affectedUsers
var query = container.GetItemLinqQueryable<SomeItem>()
    // How to check for any element in someUsers is within affectedUsers dynamically?
    .Where(item => item.AffectedUsers.Contains(someUsers[0]));

var definition = query.ToQueryDefinition();
var text = definition.QueryText;

Console.WriteLine(text);

Answer 1

要解決這個問題，需要一些基於LinqKit的神奇代碼：

public static class QueryableExtensions
{
    public static IQueryable<T> WhereAny<T, U>(this IQueryable<T> source, IEnumerable<U> items, Expression<Func<T, U, bool>> expression)
    {
        var predicate = PredicateBuilder.New<T>();

        foreach (var item in items)
        {
            Expression<Func<T, bool>> comparison = p => expression.Invoke(p, item);
            predicate = predicate.Or(comparison.Expand());
        }

        return source.Where(predicate);
    }
}

在您的工具帶中使用此方法，您可以按如下方式編寫查詢：

var query = container.GetItemLinqQueryable<SomeItem>()
    .WhereAny(someUsers, (item, user) => item.AffectedUsers.Contains(user));

生成的 cosmos 查詢將是：

SELECT VALUE root FROM root WHERE ((((ARRAY_CONTAINS(root["AffectedUsers"], "User 1")
    OR ARRAY_CONTAINS(root["AffectedUsers"], "User 2"))
    OR ARRAY_CONTAINS(root["AffectedUsers"], "User 3"))
    OR ARRAY_CONTAINS(root["AffectedUsers"], "User 4"))
    OR ARRAY_CONTAINS(root["AffectedUsers"], "User 5"))