使用页面大小和页码在Cosmos DB中分页

Question

我正在尝试使用PageSize和返回cosmosDB中的项目PageNumber.我知道我们可以设置页面大小MaxItemCount,但是我们如何将页码放在这个函数中？

这是我到目前为止所得到的:

  public async Task<IEnumerable<T>> RunSQLQueryAsync(string queryString, int pageSize, int pageNumber)
        {
            var feedOptions = new FeedOptions { MaxItemCount = pageSize, EnableCrossPartitionQuery = true };
            IQueryable<T> filter = _client.CreateDocumentQuery<T>(_collectionUri, queryString, feedOptions);
            IDocumentQuery<T> query = filter.AsDocumentQuery();
            var currentPageNumber = 0;
            var documentNumber = 0;
            List<T> results = new List<T>();
            while (query.HasMoreResults)
            {
                foreach (T t in await query.ExecuteNextAsync())
                {
                    results.Add(t);
                    documentNumber++;
                }
                currentPageNumber++;
                return results;

            }
            return null;
        }

Answer 1

目前,分页支持仅基于延续令牌.

在下面找到有关此限制的一些有趣的讨论和功能请求:

• https://github.com/Azure/azure-documentdb-dotnet/issues/377
• https://feedback.azure.com/forums/263030-azure-cosmos-db/suggestions/6350987--documentdb-allow-paging-skip-take

---继续令牌示例---

以下示例说明了一种方法(与您的方法非常相似),该方法根据所需的页码,页面大小和延续令牌查询文档:

    private static async Task<KeyValuePair<string, IEnumerable<CeleryTask>>> QueryDocumentsByPage(int pageNumber, int pageSize, string continuationToken)
    {
        DocumentClient documentClient = new DocumentClient(new Uri("https://{CosmosDB/SQL Account Name}.documents.azure.com:443/"), "{CosmosDB/SQL Account Key}");

        var feedOptions = new FeedOptions {
            MaxItemCount = pageSize,
            EnableCrossPartitionQuery = true,

            // IMPORTANT: Set the continuation token (NULL for the first ever request/page)
            RequestContinuation = continuationToken 
        };

        IQueryable<CeleryTask> filter = documentClient.CreateDocumentQuery<CeleryTask>("dbs/{Database Name}/colls/{Collection Name}", feedOptions);
        IDocumentQuery<CeleryTask> query = filter.AsDocumentQuery();

        FeedResponse<CeleryTask> feedRespose = await query.ExecuteNextAsync<CeleryTask>();

        List<CeleryTask> documents = new List<CeleryTask>();
        foreach (CeleryTask t in feedRespose)
        {
            documents.Add(t);
        }

        // IMPORTANT: Ensure the continuation token is kept for the next requests
        return new KeyValuePair<string, IEnumerable<CeleryTask>>(feedRespose.ResponseContinuation, documents);
    }

现在,以下示例说明了如何通过调用以前的方法来检索给定页面的文档:

    private static async Task QueryPageByPage()
    {
        // Number of documents per page
        const int PAGE_SIZE = 3;

        int currentPageNumber = 1;
        int documentNumber = 1;

        // Continuation token for subsequent queries (NULL for the very first request/page)
        string continuationToken = null;

        do
        {
            Console.WriteLine($"----- PAGE {currentPageNumber} -----");

            // Loads ALL documents for the current page
            KeyValuePair<string, IEnumerable<CeleryTask>> currentPage = await QueryDocumentsByPage(currentPageNumber, PAGE_SIZE, continuationToken);

            foreach (CeleryTask celeryTask in currentPage.Value)
            {
                Console.WriteLine($"[{documentNumber}] {celeryTask.Id}");
                documentNumber++;
            }

            // Ensure the continuation token is kept for the next page query execution
            continuationToken = currentPage.Key;
            currentPageNumber++;
        } while (continuationToken != null);

        Console.WriteLine("\n--- END: Finished Querying ALL Dcuments ---");
    }

Answer 2

现在可以通过新的OFFSET LIMIT子句在Cosmos DB中使用“跳过并获取”：https : //docs.microsoft.com/zh-cn/azure/cosmos-db/sql-query-offset-limit