MongoDB shell: How to remove specific elements in all the collections inside a DB

Question

I would like to remove, in all collections, all coincidences with a regex expression.

I need this, because a JSON parser failed in my app at a certain point today, and now the database is corrupted.

I could do it by hand, but I have over 100+ collections, and manually entering in mongo shell db["X"].remove({ "DateTime": { $regex : "2015-11-16" } }) for each collection would take quite a few time.

Do you know any way to perform this automatically inside mongo shell? I always access this database via package RMongo in R, and I could do it via dbRemoveQuery(rmongo.object, collection, query) but I was wondering if it could be done inside mongo shell, maybe a little quicker.

Dmytro Shevchenko · Accepted Answer · 2015-11-16T17:18:42.070

use yourDbName

// Get the names of all collections in the database.
var names = db.getCollectionNames();

// Iterate over every collection name.
for(i = 0; i < names.length; i++) {

    // Only issue the query if the collection is not a system collection.
    if(!names[i].startsWith("system.")) {

        // Issue the query against the collection with the name `names[i]`.
        db[names[i]].remove({ "DateTime": { $regex : "2015-11-16" } });
    }
}

Please note that I am excluding system collections from the list.

score 2 · Answer 2 · edited Nov 16 '15 at 11:46

2

In mongo shell:

 db.getCollectionNames().forEach(function(name) {
     db[name].remove({ "DateTime": { $regex : "2015-11-16" } });
 })

edited Nov 16 '15 at 11:46

Dmytro Shevchenko

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answered Nov 16 '15 at 11:18

SalaryNotFound

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Thanks for your effort, but (doesn't know why), didn't perform it well. – Geiser Nov 16 '15 at 11:25
@Sergio I have fixed this answer. Now it will work as well. – Dmytro Shevchenko Nov 16 '15 at 11:47
Thanks, but it was no problem of the missing `)`, I put it after it failed, but after that, I examined the collections and the documents were still there. – Geiser Nov 16 '15 at 12:00
1

@Sergio the closing `)` was not the only thing I have fixed ;-) I also added the `name` argument to the callback function and used it like this: `db[name]`. – Dmytro Shevchenko Nov 16 '15 at 12:05

score 1 · Answer 3 · answered Nov 16 '15 at 15:49

Well .startsWith() is a new technology, part of the ECMAScript 2015 (ES6) standard so it may not work in Mongo Shell.

You will need to use the .filter() method to discard system collections

var collections = db.getCollectionNames().filter(function(collection) {
    return collection.indexOf('system.') !== -1;
};

Then remove the documents that match you criteria here where "DateTime": "2015-11-16"

for(var index=0; index < collections.length; index++) {
    db[collections[index]].remove( { 'DateTime': /2015-11-16/ } )
}

MongoDB shell: How to remove specific elements in all the collections inside a DB

3 Answers3