使用 Azure Http 触发器函数应用将 Cosmos DB 与 OData 集成

Question

目标：实现 oData Azure Http 触发器功能以减少延迟。

我在 cosmosdb 中缺少 3.5 记录并使用 azure Http Trigger 函数应用程序查询数据。

我正在通过 azure Http Trigger Function 中的 azure DocumentDB 客户端查询 CosmosDB 数据。

        public static async Task<IActionResult> MachinesByRegion_Get(
        [HttpTrigger(AuthorizationLevel.Function, "get", Route = "Region/Machines")]HttpRequest req,
        ILogger log)
    {

        log.LogInformation("GetMachinesByRegion function Started to process a request.");

        // check parameters
        if (string.IsNullOrEmpty(req.Query["PageSize"]) || string.IsNullOrEmpty(req.Query["PageNumber"]))
            return new BadRequestObjectResult(new PostActionResponse(400, "Please provide valid PageSize and PageNumber"));

        // Number of documents per page
        int pageSize = int.Parse(req.Query["PageSize"]);
        Dictionary<string,string> field = new Dictionary<string, string>();
        string columns = "*";
        if (!string.IsNullOrEmpty(req.Query["Fields"]))
        {
            string columnstring = req.Query["Fields"].ToString();
            field.Add("Fields", columnstring);
            string[] columnarr = columnstring.Split(',');
            int arraylength = columnarr.Length;

            // Build Selection columns
            if (arraylength != 0)
            {
                StringBuilder strinbuilder = new StringBuilder("c.id, ");
                int i = 1;
                foreach (string value in columnarr)
                {
                    strinbuilder.Append($"c.{value.Replace(" ", String.Empty)}");
                    if (arraylength > i)
                        strinbuilder.Append(", ");
                    i++;
                }
                columns = strinbuilder.ToString();
            }
        }

        // Parse Query Parameter
        int pagenumber = int.Parse(req.Query["PageNumber"]);

        int offset = pagenumber == 1 ? 0 : (pagenumber - 1) * pageSize;

        // Bulid query string based on request
        string sqlstr = string.Format($"SELECT {columns} FROM c ORDER BY c.id ASC OFFSET {offset} LIMIT {pageSize}");


        Helper.TraceLogWriter(log, "Summary:");
        Helper.TraceLogWriter(log, "--------------------------------------------------------------------- ");
        Helper.TraceLogWriter(log, $"Collection : {DBConstants.DataBaseName.Telemetry}.{DBConstants.ContainerName.KomatsuMachine}");
        Helper.TraceLogWriter(log, $"The Query String : {sqlstr}");
        Helper.TraceLogWriter(log, "--------------------------------------------------------------------- ");
        Helper.TraceLogWriter(log, "");

        try
        {
            // Feed Options 
            var options = new FeedOptions
            {
                MaxItemCount = pageSize,
                MaxDegreeOfParallelism = -1,
                EnableCrossPartitionQuery = true,
            };

            // Create CosmosDB Connection URI
            Uri collectionUri = UriFactory.CreateDocumentCollectionUri(databaseId: DBConstants.DataBaseName.Telemetry, collectionId: DBConstants.ContainerName.KomatsuMachine);

            ConnectionPolicy connPolicy = new ConnectionPolicy
            {
                ConnectionMode = ConnectionMode.Direct,
                ConnectionProtocol = Protocol.Tcp
            };

            using var client = new DocumentClient(new Uri(BaseRepository.EndpointUri), BaseRepository.PrimaryKey, connPolicy);
            // Get the List of Items against the Query string
            var results = client.CreateDocumentQuery(collectionUri, sqlstr, options).ToList();
            int records = results.Count;
            Helper.TraceLogWriter(log, $"Retrieved Documents: {records}");

            Helper.TraceLogWriter(log, $"Sample Document: {JsonConvert.DeserializeObject(JsonConvert.SerializeObject(results[0]))}");

            await Task.Yield();

            // Build base url                    
            var pages = new PageLinkBuilder($"{BaseRepository.BaseUrl}/api/Region/Machines", pagenumber, pageSize, records, field);

            return (ActionResult)new OkObjectResult(new PagedResult
            {
                PageNumber = pagenumber,
                PageSize = records,
                Pages = pages,
                Results = results
            });
        }
        catch (Exception ex)
        {
            Helper.TraceErrorWriter(log, $"Exception caught in GetMachinesByProduct: {ex.Message}");
            return new UnprocessableEntityObjectResult(new PostActionResponse(422, "Exception in CosmosDB, Please check logs"));
        }
    }

我只想在选择、过滤和排序等情况下启用 oData 以提高性能。

在 cosmosDB 中，文档有很多字段，如果启用，它会减少数据的大小。

我对此进行了演练。
请点击这里

这是用于 Web API。 但我需要 azure Http 触发功能应用程序

Answer 1

您提供的链接仅适用于“Where”谓词，它根本不会减少选择，因为它是 IEnumerable 而不是 IQueryable ：

public async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, bool>> predicate)
    {
        IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
            UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
            new FeedOptions { MaxItemCount = -1 })
            .Where(predicate)
            .AsDocumentQuery();

        List<T> results = new List<T>();
        while (query.HasMoreResults)
        {
            results.AddRange(await query.ExecuteNextAsync<T>());
        }

        return results;
    }

我能想象你能做到的唯一方法是使用EF Core For Cosmos DB

那么您可以将Azure Functions OData 扩展与 IQueryable 结合使用。

有了它，您应该让 EF Core 直接在 CosmosDB 中为您提供特定的选择。

但这只有在您从一开始就将 EF Core 与 Cosmos DB 一起使用时才有效，因为 EF Core 对 Cosmos DB 中的 PK、Id 和鉴别器具有特定的格式。