...
mongodb doesn t seem to have the join functionality of sql. Reducing the redundancy of individual tables does not seem to make sense and affects query efficiency. and mongodb also has storage formats such as lists, which can achieve different function...
You can stream query results from MongoDB. You need to call the Query-sharpcursor () function to return an instance of QueryCursor. Please do not translate directly. I want to know what cursor is and what stream is, and why I use it, thank you! ...
there are 200000 data in the data, and each data has a typical list of words of 5000 length [{aVl1}, {bju 2},.], and typical dictionaries of 5000 length {{aRom 1}, {bjr 2},.}, use pyMongo to find100 data, the traversal of cursor is particularly slow, is...
first of all, the models of my mongoose is as follows: var clubsSchema = new mongoose.Schema({ "clubCreatetime": String, "clubCreater": String, "clubName": String, "clubDescription": String, &...
the problem is like a question. I ll describe the details in detail. asked the same question on Zhihu when I was self-taught python crawler, I came into contact with MongoDB, to install according to the URL given by rookie tutorial . Visual obser...
I tried to do this, but could not copy set initialization. ...
there is data like this: I want to use aggregate to group group by p, and then count the sum of ac, cc in each province, which can be done. The question is: I want to count the total number of tc in each province (do not repeat)? For example, Fujia...
data stores a field type (as an enumeration). When querying, it needs to be processed separately by using ifelse or switch, for example, 1 is converted to normal. I ve implemented it with the MongoDB statement, but how do I handle it in the springboot ...
ip and port are OK on the server! bind_ip 0.0.0.0 ip ask the boss to have a look. No, no, no. It s okay to pay for an answer! ...
the computer is a WIN 10 system I follow this tutorial to install mongoDB, http: www.runoob.com mongodb. but as soon as you enter the mongo link. Just report this error has been reinstalled several times, but it has not been solved. also chan...
var animalSchema = new Schema({ name: String, type: String }); animalSchema.methods.findSimilarTypes = function(cb) { return this.model( Animal ).find({ type: this.type }, cb); }; var Animal = mongoose.model( Animal , animalSchema); var dog = new A...
assume a single document type: { "_id" : ObjectId("5a19403b421aa92332bc2b32"), "id" : "95957f4a9eab11e787f1509a4c4be0cd" "incre" :1 "city" "" } data volume, 90 mill...
the company recently has a project, the main function is to manage documents, such as on the web page to view the contents of the document, and can be modified, you can also download the document to export in word format, the most important thing is to r...
Mode 1: mongod Command Mode 2: brew services start mongodb Command start what s the difference between the two ways of starting? why are there two ways? ...
suddenly became interested in mongodb, installed and started with brew according to the rookie tutorial, but showed "waiting for connections on port 27017 " for a long time, then as a front-end younger brother who still has a narrow range of knowle...
first of all, according to the description of the official document, the configuration file is created and the database path is modified. The content of the configuration file mongo.config is as follows: systemLog: destination: file path: I: ...
Virtual properties are document properties that you can get and set but that do not get persisted to MongoDB. I don t quite understand this sentence. Please do not translate. I hope you can explain it in your own words. It is better to have examples. ...
the query data is printed to see that _ id is objectID,. If it is directly converted to json,_id, it will be empty. Can you change objectID to string, and then to json? ...
the previous command is as follows: mongod --logpath C: mydatabase logs.txt --logappend --dbpath C: mydatabase --serviceName MongoDB --install however, there is no prompt on the command line after entering the carriage enter, and the service has ...
6.5 comment a b (). Next () is followed by a 6.5. Why does the second next () cause console.log (6.5) to be executed again? How to understand this problem? ...
so far, only cases with zero timestamp have been found such as 647017200 (00:00:00 on July 4, 1990) normal in other browsers safari timestampToDate: function(timestamp){ time = new Date(timestamp * 1000) var year=...
Notice: Undefined property: stdClass::$payment in Applications xxx xxx xxx xxx.php on line 48 I know I can turn it off , but I want to show the words I want to display first: for example, NameA because the other party has not sent json (or has not don...
I have a front-end project B , which is developed on the basis of project A . After the code management tool uses git, for a period of time, both project An and B move forward, and there is a partial conflict between An and B s modified code. If B wa...
Boss: my program is an instant messaging service of socket.io, and my program does not use cluster module to use cpu, so I think pm2 deployment uses pm2 s multi-input program, but when I use it, I find that the method of pm2 is equivalent to starti...