MongoError: ns not found when try to drop collection

Question

Mongoose throw an error i.e, "MongoError: ns not found" when i try to drop collection.

Here is my mongoose code:

var mongoose = require('bluebird').promisifyAll(require('mongoose'));
......
......
......   
mongoose.connection.db.dropCollection("myCollection",function(err,affect){
   console.log('err',err);

})

Error:

err { [MongoError: ns not found]
name: 'MongoError',
message: 'ns not found',
ok: 0,
errmsg: 'ns not found' }

You're not connecting to the database (using `mongoose.connect()`). — robertklep, May 10 '16 at 10:51
mongoose doesn't have drop collection method. chekout [this](http://stackoverflow.com/a/10088410/2165143) answer for more info. — Rajesh Dhiman, May 10 '16 at 10:52
@RajeshDhiman, mongoose.connection.db.dropCollection method has used, http://stackoverflow.com/questions/11453617/mongoose-js-remove-collection-or-db?answertab=active#tab-top — vineet, May 10 '16 at 11:33

score 113 · Answer 1 · answered Jun 11 '17 at 20:03

113

MongoError: ns not found occurs when performing actions on collections that don't exist.

For example, attempting to drop indexes before an explicit collection creation has occurred or before adding a document to the collection which implicitly creates the collection.

answered Jun 11 '17 at 20:03

Andrew Homeyer

7,577
4
31
26

2

So in this case, you cannot drop a collection which doesn't exist in the first place. ns is probably for namespace? – Nick Sotiros Dec 01 '17 at 06:43
3

https://github.com/mongodb/mongo/blob/acd196d77043d007b07b48b6e2c4fb13cfa5b938/src/mongo/db/catalog/drop_collection.cpp#L71 – Andrew Homeyer Dec 02 '17 at 14:01
75

Who at Mongo, Inc. thought ["ns not found" was a useful error](https://jira.mongodb.org/browse/NODE-1988)?! – Dan Dascalescu May 28 '19 at 22:53
1

Thanks all, did a check before the drop and wrapped in IF, fixed problem. App is running. – Andy Jun 27 '21 at 01:37

score 6 · Answer 2 · answered Jan 19 '20 at 09:02

Status(ErrorCodes::NamespaceNotFound, "ns not found"); is thrown when you try to drop a collection, a view or an index that doesn't exist.

For example: _dropCollection

Other than that, there is no need to explicitly check if a collection already exists before doing any CRUD operations.

score 3 · Answer 3 · answered Dec 03 '19 at 16:07

This is my mongodb connection interface to avoid drop collection error:

'use strict';

module.exports = class {
    static async connect() {
        this.mongoose = require('mongoose');

        await this.mongoose.connect(process.env.MONGODB_DSN, {
            useNewUrlParser: true,
            reconnectTries: Number.MAX_VALUE,
            reconnectInterval: 5000,
            useFindAndModify: false
        }).catch(err => {
            console.error('Database connection error: ' + err.message);
        });

        this.db = this.mongoose.connection.db;

        return this.db;
    }

    static async dropCollection(list) {
        if (list.constructor.name !== 'Array') {
            list = [list];
        }

        const collections = (await this.db.listCollections().toArray()).map(collection => collection.name);

        for (let i = 0; i < list.length; i++) {
            if (collections.indexOf(list[i]) !== -1) {
                await this.db.dropCollection(list[i]);
            }
        }
    }
};

score 0 · Answer 4 · answered May 25 '22 at 08:16

0

This is how I check the collection exists, before attempting to drop.

if (db.listCollections().toArray().includes(collection)) {
   await db.collection(collection).drop();
}

answered May 25 '22 at 08:16

Dan

1
1

MongoError: ns not found when try to drop collection

4 Answers4

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