javascript - Mongoose - Version Error: No matching document found for id

Question

Context: I have a Post Mongoose model that contains a csv_files array field to store csv strings. I make a fetch API request from a different web app to POST the csv strings for a particular Post.

The code below produces an error

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): VersionError: No matching document found for id "5966932399e969ad8013bedf"

router.js

router.post('/posts/:url/upload-csv/:csv_name', (req, res) => {
  let csv_name = req.params.csv_name;
  let csv_string = csv_name+req.body.csv_string;

  Post.findOne({url: req.params.url})
    .then((post) => {
      if (post.csv_files.length === 0) {
        post.csv_files.push(csv_string);
      } else {
        let foundExistingCSV = false;
        for (var i = 0; i < post.csv_files.length; i++) {
          if (post.csv_files[i].includes(csv_name)) {
            foundExistingCSV = true;
            post.csv_files[i] = csv_string;
            break;
          }
        }
        if (!foundExistingCSV) post.csv_files.push(csv_string);
      }

      post.markModified('csv_files');
      post.save();

      return res.status(200);
    })
    .catch((err) => {
      console.log(err);
      return res.status(400);
    });
});

models/post.js

const mongoose    = require('mongoose');

var stringPreset = {
  type: String,
  uppercase: true
}

var Post = mongoose.model('Post', {
  name                 : stringPreset,
  url                  : String,
  password             : String,
  csv_files            : { type : Array , "default" : [] },
  updatedAt            : { type: Date, default: Date.now }
});

module.exports = { Post };

How can I fix this so that the document saves into the csv_files array without the error?

Answer 1

When saving an object to Mongo DB you have to understand that Mongo DB has a version control system in place. This helps ensure that if you save an object once, when saving it again you don't end up overwriting the previously saved data.

This is the error you're seeing. If you want to force the object to update regardless of version control in this particular instance you may want to use .update() instead. This will force the object to be updated regardless of its currently saved state.

This is because .save() watches and cares about version controls, while .update() will update the object regardless of version control.