I would like to delete all documents in all MongoDB collections. Is there a way to delete all documents in all collections.
I was using db.collection.remove({}) but it only removes all documents in one collection. Is there any command to do? I'm using NodeJS mostly, maybe there is a chance to use NodeJS to delete all documents in all collections?
Sorry if the question is dumb, just started working in MongoDB.
As already suggested - You can either use .dropDatabase() to drop entire database or .collection.drop() to drop a collection or if it's just to delete all documents in all collections then you need to iterate on list of collections and implement either .collection.remove() or .collection.deleteMany() or .findAndModify() without any filter in query condition.
To delete documents in each collection individually :
first list all collection names using .getCollectionNames() and then remove documents.
let colls = db.getCollectionNames() // Mongo shell can accept .Js Func's, if you've more collections you can use parallel as well
colls.forEach(eachColl => db[eachColl].remove({})) // or .deleteMany() or . findAndModify()
Doing this way, you'll still have the database and empty collections existing on MongoDB server. Maybe you can comeback after sometime check list of collections available or maybe rename few etc.
But if you just simply don't want to look at collection names that use to exist in any near future, go ahead with drop commands preferable drop database as you wanted to delete all docs from all collections - why it's preferred ? is because unlike SQL databases MongoDB automatically creates a database and a collection if you write a document for the first time to a collection in a DB. So in MongoDB you might not need to maintain databases with empty collections.
Assume you're querying on collection named girlfriend which is in mylife database - Let's say it's already deleted/missing/never existed then .find() would return [] empty array same like querying on empty collection on a DB - this is the advantage with MongoDB as it doesn't throw an error on mismatched names.
Related
I have a collection in mongoDB that hold 66000 documents on it, Now I want to add new filed to all theses document a uniqueID field which take this form S-1111 and the number increase for the next document
I have tried to make a call to DB and update each one in order but it take to much time because this is a lot of request to mongoDB , so is there is another way to do that fast
I am working with Node and mongoose
I have a basic express app and im getting started with db queries and i want to know how to avoid multiple db queries because i dont think its efficient the way i do it :
app.get('/:word', function(req,res){
db.create({'name': word});
console.log('the word is ' + word);
});
What i want to do is :
get the word from the url
check if it exists in the datbaase (or previously requested because if it was then it was probably added already through this basic code)
if it doesn't exist then add it and then proceed to console.log
I want to add each word to my database once only and not run the db query again and again.
Here's what im thinking :
Not so efficient way
query to check if it exists before inserting one
Good way but i dont know how to start here
Cache the word being queried and maintain cache to prevent db queries
More info edit
I'm using mongodb via mongoose
the 'word' key is already unique so i know its not creating duplicate values
i dont want to run ANY db queries if that value or that url has already been hit once
The only way to check if the word already exists is to query the database before inserting. There are libraries (and also database) that implements the findOrCreate method, but this is always just an abstraction. Behind the scenes, the database will search for an existing value before writing.
If your database is huge and queryng is not suitable, you could use a cashing system (like Redis). But this definitely depends on your logic and your data size.
Probably you can just optimize the process just adding and index to the column you want be unique (I guess it's name?).
You could also define the column name as unique. When inserting, the database will throw you an error if the document already exists. But keep in mind again that, behind the scenes, the database is queryng for an existing same value before inserting. The advantage to have an "unique" column is that the index for this column is automatically created and also from your app logic (node js) you can just call the insert method and add a little bit error handling logic.
MongoDB will create any collections you use in your app if they do not already exist.
Insert Unique Value :
Create Unique Index to your key, So that the value will be added only once. If you try to add again it will throws an error to you.
To create Unique Index,
db.collection.createIndex( { "name": 1 }, { unique: true } )
Caching :
For caching, Store your data on cache system(Like: memory-cache, redis) on first time data will be query from MongoDB and then for subsequent need of data you can use cache system.
In mongo db you can use findOneAndUpdate with optional flag upsert: true documentation
To ensure that every word appears only once you should also set unique index on that field. However rememer that unique index is case sensitive so Cat and cat are different words.
I am working on a node.js app, and I've been searching for a way around using the Model.save() function because I will want to save many documents at the same time, so it would be a waste of network and processing doing it one by one.
I found a way to bulk insert. However, my model has two properties that makes them unique, an ID and a HASH (I am getting this info from an API, so I believe I need these two informations to make a document unique), so, I wanted that if I get an already existing object it would be updated instead of inserted into the schema.
Is there any way to do that? I was reading something about making concurrent calls to save the objects, using Q, however I still think this would generate an unwanted load on the Mongo server, wouldn't it? Does Mongo or Mongoose have a method to bulk insert or update like it does with insert?
Thanks in advance
I think you are looking for the Bulk.find(<query>).upsert().update(<update>) function.
You can use it this way:
bulk = db.yourCollection.initializeUnorderedBulkOp();
for (<your for statement>) {
bulk.find({ID: <your id>, HASH: <your hash>}).upsert().update({<your update fields>});
}
bulk.execute(<your callback>)
For each document, it will look for a document matching the {ID: <your id>, HASH: {your hash}} criteria. Then:
If it finds one, it will update that document using {<your update fields>}
Otherwise, it will create a new document
As you need, it will not make a connection to the mongo server on each iteration of the for loop. Instead a single call will be made on the bulk.execute() line.
I'm pulling data from a RETS(XML) feed and saving it in a local MongoDB using node and mongoose.
Periodically I need to update the documents and delete the inactive ones as well as add new ones. Rather than making multiple queries to Mongo or the RETS server, I was pulling both and looping through the data.
This works fine but is there a way to save the Mongoose results back to the database with updates and inserts? Or do I need to find each document and update it individually?
On MongoDB, to update multiple documents (not just one) using Mongoose you can use the multi option:
Model.updateMany({
size: 'lage'
}, {
$set: { size: 'large' }
});
See more on in the Mongoose documentation for updating documents and here
For completeness, If any one has multiple query conditions and want to add new fields for every matching documents of query condition then we can go with
var bulk = Person.collection.initializeUnorderedBulkOp();
bulk.find(query1).update(update1);
bulk.find(query2).update(update2);
bulk.execute(callback);
In following documentation, it is said that db.collection.initializeUnorderedBulkOp()
Initializes and returns a new Bulk() operations builder for a
collection. The builder constructs an unordered list of write
operations that MongoDB executes in bulk. MongoDB executes in
parallel the write operations in the list.
https://docs.mongodb.org/v3.0/reference/method/db.collection.initializeUnorderedBulkOp/
I have a Tags collection which contains documents of the following structure:
{
word:"movie", //tag word
count:1 //count of times tag word has been used
}
I am given an array of new tags that need to be added/updated in the Tags collection:
["music","movie","book"]
I can update the counts all Tags currently existing in the tags collection by using the following query:
db.Tags.update({word:{$in:["music","movies","books"]}}, {$inc:{count:1}}), true, true);
While this is an effective strategy to update, I am unable to see which tag values were not found in the collection, and setting the upsert flag to true did not create new documents for the unfound tags.
This is where I am stuck, how should I handle the bulk insert of "new" values into the Tags collection?
Is there any other way I could better utilize the update so that it does upsert the new tag values?
(Note: I am using Node.js with mongoose, solutions using mongoose/node-mongo-native would be nice but not necessary)
Thanks ahead
The concept of using upsert and the $in operator simultaneously is incongruous. This simply will not work as there is no way to different between upsert if *any* in and upsert if *none* in.
In this case, MongoDB is doing the version you don't want it to do. But you can't make it change behaviour.
I would suggest simply issuing three consecutive writes by looping through the array of tags. I know that's it's annoying and it has a bad code smell, but that's just how MongoDB works.