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Appending to child collection in MongoDB

Torgeir "Tor" Helgevold
- JavaScript Developer and Blogger
Published: Wed Mar 18 2015

In the following post I will show how to append documents to an existing array of sub documents using Mongoose and MongoDB.

Mongoose lets you define mongo documents with sub documents, but it also offers a great shortcut to appending to the child collection.

Assume the following schema consisting of a language schema with belonging translations in a child collection.

var translation = { key:{type: String,required: true }, text:{type: String}, createdDate:{type: Date, default: Date.now} }; var languageSchema = new mongoose.Schema({ code:{type:String, required: true}, name:{type:String, required: true}, isDefault:{type:Boolean, default:false}, translations:[translation] },{ versionKey: false });

It turns out that Mongoose provides a handy short cut for appending to the translations in a single update statement. The statement below will append the same set of translations to the translations collection of all language documents. However, you can also add a filter if you want to limit the set of language documents to update.

var translations = [...] //translations to add languageModel.update({}, { $push: { translations: { $each: translations } } }, { multi: true }).exec();

The key to this are the $push and $each operators.

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