How to use Mongo's findOneAndUpdate.

[majidhassan]

Hello,

I'm trying to update a single object atomically as it could be written to from multiple users at - more or less - the same time. This should be done using collection.findOneAndUpdate. Is there any way I can use this within Parse, without having to use Mongo's NodeJS client?

[flovilmart]

you could use it via cloudCode, and maintain your own connection to mongoDB and run those operations atomically.

Note that many operations are already atomic (like increment, addUnique etc...)

[majidhassan]

Hey @flovilmart,

I already run my own connection from cloud code. My question was, whether there's a "parse" way to do it, or whether I have to implement it using the NodeJS Mongo client.

Also, regarding increment and other functions, I've tried them, and - unlike findOneAndUpdate - they don't force a write lock on the collection / document when I tried them.

[oallouch]

same question here
I guess I'll go the mongo-driver-way.

[yomybaby]

On the mongodb, findOneAndUpdate of adapter uses findAndModify of mongoDB collection. (code)

findAndModify method is also atomically update. (docs)

So I use this way on cloud code :

Parse.Cloud.define('borrowBookFromLibrary', function(request, response) {
  const { amount, bookId } = request.params;
  
  const {
    AppCache
  } = require('parse-server/lib/cache'); // this refrenese only in cloud cloud
  const app = AppCache.get(process.env.APP_ID);
  
  if(!amount || amount <= 0 || ! bookId) { // some validation
    response.error('invalid');
  }
  const schema = { // you don't have to write all specifics here, but have to have fields object.
    fields: {
    }
  };
  
  const query = {
    objectId: bookId,
    available: {
      $gte: amount
    }
  };

  const update = {
    available: {
      "__op": "Increment",
      "amount": amount * -1
    },
    history: {
      "__op": "Add",
      "objects": [{
        by: 'James',
        requestDate: new Date()
      }]
    }
  };
  
  app.databaseController.adapter.findOneAndUpdate(
    'BookLibrary',
    schema,
    query,
    update
  ).then((result) => {
    if (result) {
      response.success({ success: true });
    } else {
      response.error({ error: true })
    }
  });
});