Collection (MongoDB) update very poor performance

I’m having issues optimising update performance for a Meteor collection.

I take a document from one collection (CollectionA), modify it, cherry-pick some of the content, and then update a near duplicate of it in another collection (CollectionB). I also upsert in case new documents have been added to CollectionA

Everything happens in a few milliseconds, but the update can take anywhere from 10–30+ seconds depending on the size of the document being updated. The documents are typically around 30kb…

I have tried without Meteor.defer, with writeConcern : 0, and on both local and cloud replica set clusters. Have also tried using insert instead of update. Nothing makes a noticeable difference.

CollectionA.find({isPublished : true, "approval.status" : { $gte : 1 } }).forEach((doc)=>{

    let newDoc = {
        parentId : doc._id,
        slug : doc.slug, // these never change, only the content array changes...
        title : doc.title,
        description: doc.description,
        tags : doc.tags,
        category : doc.category,
        createdAt : new Date(),
        content: [...,...,...] // the content of the new document is cherrypicked from the parents before saving

    while(doc.content.length) {
        // cherry-picking and pushing to newDoc.content
        // super quick, a couple of MS

        CollectionB.update({parentId : doc._id}, {$set : newDoc}, {upsert : true}, (err,res)=>{
            if (!err) {
                console.log(`Saved child for ${doc.title}`);
            } else {
                console.log(`Error saving child for ${doc.title}: ${err}`);


and do u have index on parentId when you want to insert by querying it first ?
how is it with inserting to CollectionB without schema? from mongo shell ?
and is better if you want to just insert more entries and insert operations dont need to be executed in exact order. forEach cares about order, so waits as long as I know

1 Like


Not familiar with MongoDB but here is a possible resource.
All the things is discussed properly.

Hope it will help… :slight_smile: