在 Cosmos DB 中使用页大小和页码进行分页 [英] Pagination in Cosmos DB using Page Size and Page Number

问题描述

我正在尝试使用 PageSize 和 PageNumber 从 cosmosDB 返回项目.我知道我们可以在MaxItemCount中设置页面大小，但是我们如何在这个函数中放置页码?

I am trying to return items from cosmosDB using PageSize and PageNumber. I know we can set the page size in MaxItemCount, but how do we put the page number in this function?

这是我目前得到的:

  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;
        }

推荐答案

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讨论和功能请求:

Find below some interesting discussion and feature request about this limitation:

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

--- 连续令牌示例---

以下示例说明了一种根据所需页码、页面大小和继续标记查询文档的方法(与您的方法非常相似):

The following example illustrates a method (very similar to yours) that queries documents based on the desired page number, page size and continuation token:

    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，以下示例说明如何通过调用前面的方法来检索给定页面的文档:

Now, the following example illustrates how to retrieve documents for a given page by calling the previous method:

    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("
--- END: Finished Querying ALL Dcuments ---");
    }

这篇关于在 Cosmos DB 中使用页大小和页码进行分页的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！