computed.sort slows down and hangs when sortProperties change

[RandomEtc]

It seems that computed.sort can slow to a crawl and hang browsers if the sortProperty is changed too often.

Here's a minimal demo using computed.sort: http://jsbin.com/bagalowo/3/edit Click the table headers to re-order. After 10-15 times things get noticeably slow.

The TableController is pasted below for reference. The sort action on the table headers modifies the sortProperty which in turn is used be computed.sort to update the sortedRows. It works, but each time sortProperty changes, the internals of computed.sort take up more and more time.

Theory: it appears that the multiple calls to setupSortProperties.call(this); and the sortPropertyDefinitions.addObserver('@each', this, updateSortPropertiesOnce); line are interacting badly and updateSortPropertiesOnce is filling up the run-loop with redundant work? Here's the relevant part of 1.5 - https://github.com/emberjs/ember.js/blob/v1.5.0/packages/ember-runtime/lib/computed/reduce_computed_macros.js#L685 - I've confirmed this is also an issue in the latest canary, used in the above jsbin.

SortApp.TableController = Ember.Controller.extend({
  rows: [
    { name: 'Ian', age: 14 },
    { name: 'John', age: 12 },
    { name: 'Karen', age: 13},
    { name: 'Lisa', age: 10 },
    { name: 'Mike', age: 19 }
  ],
  sortedRows: Ember.computed.sort('rows','sortProperty'),
  sortProperty: Ember.A(['age:asc']),
  actions: {
    sort: function(property) {
      var sortProperty = this.get('sortProperty');
      var currentSort = sortProperty[0].split(':');
      if (currentSort[0] == property) {
        var dir = currentSort[1] == 'asc' ? 'desc' : 'asc';
        sortProperty[0] = property+':'+dir;
      } else {
        sortProperty[0] = property+':asc';
      }
      this.set('sortProperty', sortProperty);
    }
  }
});

cc @hjdivad @ebryn as follow-up from https://twitter.com/RandomEtc/status/455030469138997248

PS some workarounds: use a computed property to create an ArrayProxy with SortableMixin instead, or refactor to use an ArrayController with arrangedContent if possible.

[krisselden]

closing as duplicate of #4740