data11GB,:
the amount of db.collection.stats () data is the same. What is the reason for this? Are there any relevant resources available?
beside the point, there has been master/slave replication in the history of MongoDB (in fact, it still exists). Strictly speaking, the master and backup usually refers to that thing. What we are using now is basically the replication set (replica set).
besides, your situation is actually normal. The principle is the same as the fact that your disk will be fragmented if you use it for a long time. Especially if you have deleted data on a large scale. To explain simply, suppose you have four doc1/doc2/doc3/doc4 documents in your table, and the order in which they are stored on disk is:
doc1 | doc2 | doc3 | doc4
now that you have deleted the doc2, disk, the space usage becomes
doc1 | (blank) | doc3 | doc4
the system has no way to release this blank space unless you clean up the disk and move the blank space to the end:
doc1 | doc3 | doc4 | (blank)
then the system can truncate the white space at the end of the file. Free up this space. As you can see, moving white space to the end of the file is a time-consuming and laborious operation, and the easiest way is to move all the subsequent documents forward to fill the gaps left by doc2 (as shown above, doc3/doc4 has been moved forward). However, this involves a large number of disk Imando, which can have a serious impact on performance. Of course, there are other ways to defragment the disk, but no matter which one, it will cause a serious impact on Icano, so we don't usually do this kind of defragmentation. The way to defragment is compact command . As mentioned earlier, because it has a serious impact on performance, this is generally done only during maintenance time. And even if you don't do this, the system knows where it is blank, and when new documents come in, it will try to reuse these blank parts to maximize space utilization. However, no matter how good the algorithm, space reuse must not be 100%, because the new document can never be exactly as big as the previously deleted document, so you can only find a larger space than the new document to use. This leaves a smaller fragment that is more difficult to reuse.
another workaround is to delete the node content and do Synchronize again. Because Synchronize is equivalent to grabbing all the documents and rewriting them to disk one by one, the documents are compactly arranged on disk after Synchronize is completed, which is equivalent to defragmentation. And in this process, the slave node is affected, which does not provide services in the Synchronize process, so the impact on the online is the least. Note, however, that it will also have an impact on the primary node, because it has to read all the data on the primary node, and the increase of the Ibino of the primary node is inevitable.
finally, back to your question, why the slave node is smaller than the master node should have been explained above.
Previous: If the calculation property of VUE2.0 cannot be passed, how can my requirements be realized?
Next: Bug caused by different sources of npm cnpm installation packages
Project.updateOne(r, { $pull: { thunder2: { files: { _id: "5ab362d446f15936bcea7dd3" } } } }, function(err, data) { if (err) { res.send("") } else { ...
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 ...
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? ...
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. ...
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: ...
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...
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? ...
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...
assume a single document type: { "_id" : ObjectId("5a19403b421aa92332bc2b32"), "id" : "95957f4a9eab11e787f1509a4c4be0cd" "incre" :1 "city" "" } data volume, 90 mill...
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...
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...
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! ...
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 ...
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...
I tried to do this, but could not copy set initialization. ...
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...
first of all, the models of my mongoose is as follows: var clubsSchema = new mongoose.Schema({ "clubCreatetime": String, "clubCreater": String, "clubName": String, "clubDescription": String, &...
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...
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! ...
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...