c# - DocumentDb DocumentClient 获取前 25 个文档

Question

Cosmos 入门和文档 db/sql。为什么这不起作用？我可以看到，没有抛出任何错误。有数据应该返回。

    private const string EndpointUri = "some url";
    private const string PrimaryKey = "somekey";
    private const string DbId = "People";
    private const string CollectionId = "Person";
    private DocumentClient client;

    // GET: api/Person
    [HttpGet]
    public IEnumerable<Person> Get()
    {
        this.client = new DocumentClient(new Uri(EndpointUri), PrimaryKey);
        FeedOptions queryOptions = new FeedOptions { MaxItemCount = 25, EnableCrossPartitionQuery = true };



        IQueryable<Person> personQuery = this.client.CreateDocumentQuery<Person>(
            UriFactory.CreateDocumentCollectionUri(DbId, CollectionId), queryOptions)
            .Where(f => f.NameFirst != "Andersen");

        List<Person> retVal = new List<Person>();
        retVal = personQuery.ToList();
        return retVal;
    }

Answer 1

MaxItemCount 是每次枚举操作将获得的最大元素数。它不会返回前 25 个文档，而是返回每个枚举 25 个文档的聚合批处理中与此查询匹配的所有文档。

如果您想要前 25 项，您的代码应如下所示:

[HttpGet]
public async Task<IEnumerable<Person>> Get()
{
    this.client = new DocumentClient(new Uri(EndpointUri), PrimaryKey);
    FeedOptions queryOptions = new FeedOptions { EnableCrossPartitionQuery = true };

    var personQuery = this.client.CreateDocumentQuery<Person>(
        UriFactory.CreateDocumentCollectionUri(DbId, CollectionId), queryOptions)
        .Where(f => f.NameFirst != "Andersen").Take(25).AsDocumentQuery();

    List<Person> retVal = new List<Person>();

    while(personQuery.HasMoreResults)
    {
        var results = await personQuery.ExecuteNextAsync<Person>();
        retVal.AddRange(results);
    }

    return retVal;
}

根据您在集合中索引字符串的方式，您可能还需要将 FeedOptions 对象的 EnableScanInQuery 属性设置为 true。