Why would a database named 'blog' not allow a record insert and also give no return error and why would a database named 'blogs' allow a record inserts and return errors?
I just spent several hours going through all my code thinking I did something wrong. I have written many mongoose connected apps but when using the following it would return success but not insert the record and return no error as to why:
mongooose.connect('mongodb://localhost:27017/blog');
After banging my head against a wall for a bit I decided to change the database name:
mongooose.connect('mongodb://localhost:27017/blogs');
It works! But why would this name convention matter? I can't find anything in the documentation for MongoDB or Mongoosejs.
So I'm fairly certain mongodb doesn't care about database name "blog" vs "blogs". However, do note that mongoose has the questionably-helpful feature of silently queueing up operations while the database connection is still not established and then firing them off if/when the database connection is ready. That could be causing your confusion. To test that theory, pass a callback to mongoose.connect and put a console.log in the callback so you know exactly when the connection is ready.
Related
I receive 3 post calls from client, let say in a second, and with nodejs-mongodb immediately(without any pause, sleep, etc) I try to insert the data that is posted in database using updateOne. All data is new, so in every call, insert would happen.
Here is the code (js):
const myCollection = mydb.collection("mydata")
myCollection.updateOne({name:req.data.name},{$set:{name:req.data.name, data:req.data.data}}, {upsert:true}, function(err, result) {console.log("UPDATEONE err: "+err)})
When I call just 1 time this updateOne, it works; 2 times successively, it works. But if I call 2+ times in succession, only the first two ones correctly inserted into database, and the rest, no.
The error that I get after updateOne is, MongoWriteConcernError: No write concern mode named 'majority;' found in replica set configuration. However, I always get this error, also even when the insertion is done correctly. So I don't think this is related to my problem.
Probably you will suggest to me to use updateMany, bulkWrite, etc. and you will be right, but I want to know the reason why after 2+ the insertion is not done.
Have in mind .updateOne() returns a Promise so it should be handled properly in order to avoid concurrency issues. More info about it here.
The error MongoWriteConcernError might be related to the connection string you are using. Check if there is any &w=majority and remove it as recommended here.
I'm working on a node.js app that uses MongoDB and I read this from the docs:
db.collection
Fetch a specific collection (containing the actual collection information). If the application does not use strict mode you can can use it without a callback in the following way.
var collection = db.collection('mycollection');
First of all, what 'strict mode' is the doc referring to?
Also, is it a bad practice to grab the collection in this fashion? Without the callback, wouldn't I lose the ability to capture a potential connection error when trying to select the right collection?
db.collection('some_collection', function(err, collection) {
// query goes here
});
http://mongodb.github.io/node-mongodb-native/api-generated/db.html#collection
strict, (Boolean, default:false) returns an error if the collection
does not exist
Right there in the documentation.
That is there so your application may not create new collections itself and can only reference what has been created before. Hence the need for the callback, in order to trap the error.
It might be referring to Javascript's strict mode instead of a Mongo specific feature. strict mode enables some optional but backwards incompatible changes in the Javascript language that help catch some bugs:
What does "use strict" do in JavaScript, and what is the reasoning behind it?
I am new to CouchDB / PouchDB and until now I somehow could manage the start of it all. I am using the couchdb-python library to send initial values to my CouchDB before I start the development of the actual application. Here I have one database with templates of the data I want to include and the actual database of all the data I will use in the application.
couch = couchdb.Server()
templates = couch['templates']
couch.delete('data')
data = couch.create('data')
In Python I have a loop in which I send one value after another to CouchDB:
value = templates['Template01']
value.update({ '_id' : 'Some ID' })
value.update({'Other Attribute': 'Some Value'})
...
data.save(value)
It was working fine the whole time, I needed to run this several times as my data had to be adjusted. After I was satisfied with the results I started to create my application in Javascript. Now I synced PouchDB with the data database and it was also working. However, I found out that I needed to change something in the Python code, so I ran the first python script again, but now I get this error:
couchdb.http.ResourceConflict: (u'conflict', u'Document update conflict.')
I tried to destroy() the pouchDB database data and delete the CouchDB database as well. But I still get this error at this part of the code:
data.save(value)
What I also don't understand is, that a few values are actually passed to the database before this error comes. So some values are saved() into the db.
I read it has something to do with the _rev values of the documents, but I cannot get an answer. Hope someone can help here.
I am facing a problem with mongoose Model.create method.
When i call
Model.create(arrayOfThousandDocs, function(err){});
After 15 min (sufficient for all the docs to get saved) when i switch to mongo shell and query upon total no of docs saved
then i find only something around 700-800 (no of docs saved varies every time Model.create is called).
And mongoose or mongo returns no any error.
Have anyone faced the same bug?
Please tell me how to resolve it.
it may be because, Model.create uses forEach method, and that is not suitable in nodejs asynchronous mode programming.. Please correct me if if i am wrong..
and suggest your views..
here is the source : http://mongoosejs.com/docs/api.html#model_Model.create
I just want to know if when I set a mongoose connection and I define some models, (previously adding their appropriate requires on app.js, or wathever), the model, if not exist, will be created automatically the first time when I run node app.js?
Is this kind of logic correct?
If not, do I have to create before my mongoDB collections, models and so on?
I was thinking to an automatic creation of the mongo db collection when I first run the app.js
Thanks!
Michele Prandina
Schemas (and models) are a client-side (node.js) manifestation of your data model. A few things, like the indexes you've defined, are created upon first use (like saving a document for example). Nearly everything else is delay created, including collections.
If you want consistent behavior regarding your models (and their associated schemas), you'll need to make sure they're loaded prior to any access of the associated database. It doesn't really matter where you put them, as long as they are created/executed prior to usage. You might for example:
app.js
models\Cheese.js
\Cracker.js
Then, in app.js:
var Cheese = require('Cheese.js');
var Cracker = require('Cracker.js');
Assuming, of course, you've exported the models:
model.exports = mongoose.model('Cheese',
new mongoose.Schema({
name: String,
color: String
})
);