Bulk operations

[michielbdejong]

• When data comes in from the server, instead of doing one IDB transaction per change (see https://github.com/Kinto/kinto.js/blob/master/src/adapters/IDB.js#L110), do only one IDB transaction, containing all the updates (e.g. importing 1000 records into an empty database)
• For Collection#create, Collection#update and Collection#delete, if an Array is passed instead of an object, apply the operation to each element of this array, but in one single IDB transaction.

Background:
This code:

var kinto = new Kinto();
var coll = kinto.collection('foo');
var requests = [];
for (var i=0; i<1000; i++) {
  requests.push(coll.create({ num: i }));
}
var startTime = new Date().getTime();
console.log("Starting");
Promise.all(requests).then(results => {
  console.log("Finished, ms:", new Date().getTime() - startTime)
}, err => console.error(err));

Outputs:

Object { Symbol(record)_3.999wfjax45: Object }
Starting
Finished, ms: 2144

It takes more than 2000 milliseconds on B2G-Desktop on my Macbook to store 1000 items in Kinto.js, so that's a lot, especially if we translate that to low-end devices on which our FxOs Sync app will have to run.