mongos> var it = db.test.find({'i': 1, "old_id": {$exists: 1}}) 遍历计数1:mongos> var count = 0;while(it.hasNext()){if (it.next()["X"].length==32)++count}print(count) 遍历计数2:mongos> var count = 0;while(it.hasNext()){var item = it.next(); if (item['X']...
We will use count_documents method to do so: >>> races.count_documents({}) 9040 Powered By Notice the empty dictionary passed to count_documents. That dictionary is called a filter in MongoDB. As we go through the tutorial, we will learn how to fill the dictionary to create ...
Learn how to monitor a MongoDB instance and which metrics you should consider to optimize performance.
A QueryCursor is a concurrency primitive for processing query results one document at a time. A QueryCursor fulfills the Node.js streams3API, in addition to several other mechanisms for loading documents from MongoDB one at a time. 总之,QueryCursor 可以每次从 MongoDB 中取一个 document,这样显...
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(3)在返回的数据中,“acknowledged”为“true”表示删除成功,“deletedCount”表示一共删除了1条数据 (4)再次查询example_data_1,发现已经找不到被删除的数据了 提示:慎用删除功能。一般工程上会使用“假删除”,即:在文档里面增加一个字段“deleted”,如果值为0则表示没有删除,如果值为1则表示已经被删除了。默认...
How to use a case-insensitive index in a find() or aggregate() query How to make the most of MongoDB’s aggregation framework to move complexity from the app layer to the database layer As next steps, I suggest you now take a look at the AWS documentation to learn how to deploy ...
DeprecationWarning: Collection.remove() is deprecated. Use deleteOne, deleteMany, findOneAndDelete, or bulkWrite. { acknowledged: true, deletedCount: 1 } 这样我们就把20岁的沙僧给删掉了 这个remove默认就是删除一个对象,看官方文档中: 现在数据库中有两个金角大王,然后,我们需要同时删除这两个 ...
NamePathTypeDescription deletedCount deletedCount integer deletedCount Find DocumentOperation ID: FindDocument Using the findOne endpoint will let you retrieve a single document from a collection. Use the filter property in the request body to specify the search criteria. If more than one document mat...
gte(4.5).toConstructor(); // use it! const n = await greatMovies().count(); console.log('There are %d great movies', n); const docs = await greatMovies().where({ name: /^Life/ }).select('name').find(); console.log(docs);...