azure - DocumentDB - 查询结果顺序

Question

我正在使用 Azure DocumentDB 来存储有关用户的信息。这些文档包含一个名为date_created的属性。我想向 documentDB 发送查询以检索存储在该集合中的所有用户。我还希望结果按从最新到最旧的顺序排列。

我目前在 DocumentDB 中实现了一个存储过程，它遍历集合并根据日期属性对结果进行排序。不过，我有两个问题:

1. 当查询返回多个文档时，DocumentDB 使用的默认顺序是什么？

2. 我了解 DocumentDB 尚不支持排序控制，但如果我使用存储过程对结果进行排序，我是否正在执行完整的集合扫描，或者数据库是否至少利用属性的索引我正在排序？作为引用，我使用的存储过程是这个(根据产品团队提供的 Azure 示例稍作修改):

   function orderBy(filterQuery, orderByFieldName, continuationToken) { 
   // HTTP error codes sent to our callback funciton by DocDB server. 
   var ErrorCode = { 
       REQUEST_ENTITY_TOO_LARGE: 413, 
   }
   var collection = getContext().getCollection(); 
   var collectionLink = collection.getSelfLink(); 
   var result = new Array(); 
   
   tryQuery({}); 
   
   function tryQuery(options) { 
       var isAccepted = (filterQuery && filterQuery.length) ? 
           collection.queryDocuments(collectionLink, filterQuery, options, callback) : 
           collection.readDocuments(collectionLink, options, callback) 
   
       if (!isAccepted) throw new Error("Source dataset is too large to complete the operation."); 
   } 
   
   /** 
   * queryDocuments callback. 
   * @param {Error} err - Error object in case of error/exception. 
   * @param {Array} queryFeed - array containing results of the query. 
   * @param {ResponseOptions} responseOptions. 
   */ 
   function callback(err, queryFeed, responseOptions) { 
       if (err) { 
           throw err; 
       } 
   
       // Iterate over document feed and store documents into the result array. 
       queryFeed.forEach(function (element, index, array) { 
           result[result.length] = element; 
       }); 
   
       if (responseOptions.continuation) { 
           // If there is continuation, call query again providing continuation token. 
           tryQuery({ continuation: responseOptions.continuation }); 
       } else { 
           // We are done with querying/got all results. Sort the results and return from the script. 
           result.sort(compare); 
   
           fillResponse(); 
       } 
   } 
   
   // Compare two objects(documents) using field specified by the orderByFieldName parameter. 
   // Return 0 if equal, -1 if less, 1 if greater. 
   function compare(x, y) { 
       if (x[orderByFieldName] == y[orderByFieldName]) return 0; 
       else if (x[orderByFieldName] < y[orderByFieldName]) return 1; 
       return -1; 
   } 
   
   // This is called in the very end on an already sorted array. 
   // Sort the results and set the response body. 
   function fillResponse() {
       var page_size = 20;
       // Main script is called with continuationToken which is the index of 1st item to start result batch from. 
       // Slice the result array and discard the beginning. From now on use the 'continuationResult' var. 
       var continuationResult = result; 
       if (continuationToken) continuationResult = result.slice(continuationToken); 
       else continuationToken = 0;
   
       if (page_size > continuationResult.length ) {
           page_size = continuationResult.length;
       }
   
       // Get/initialize the response. 
       var response = getContext().getResponse(); 
       response.setBody(null); 
   
       // Take care of response body getting too large: 
       // Set Response iterating by one element. When we fail due to MAX response size, return to the client requesting continuation. 
       var i = 0;
       var final_result = [];
       for (; i < page_size; ++i) { 
           try { 
               // Note: setBody is very expensive vs appendBody, use appendBody with simple approximation JSON.stringify(element).
               final_result.push(continuationResult[i]);                   
           } catch (ex) { 
               if (!ex.number == ErrorCode.REQUEST_ENTITY_TOO_LARGE) throw ex; 
               break; 
           } 
       } 
   
       /* Now next batch to return to client has i elements. 
       // Slice the continuationResult if needed and discard the end. */
       var partialResult = continuationResult; 
       var newContinuation = null; 
       if (i < continuationResult.length) { 
           partialResult = continuationResult.slice(0, i); 
       }
   
       // Finally, set response body.          
       response.setBody({ result: final_result, continuation: i }); 
   } 
   

   }

Answer 1

更新:截至 2015 年 7 月 - DocumentDB 在查询中支持 ORDER BY

目前，您需要在客户端或存储过程上对集合进行排序(尽管我建议在客户端上这样做，因为存储过程的执行是有限的)。

回答您的问题:

1) 我不相信有保证的默认排序

2) 存储过程将导致集合扫描，然后对其进行排序。

您可以通过在 Azure 反馈论坛上发表意见来帮助插入“排序依据”: http://feedback.azure.com/forums/263030-documentdb/suggestions/6334829--order-by-in-queries