Gzip rules the world of optimization, often

So I have a massive chunk of JSON that a Django view is sending to a piece of Angular that displays it nicely on the page. It's big. 674Kb actually. And it's likely going to be bigger in the near future. It's basically a list of dicts. It looks something like this:

>>> pprint(d['events'][0])
{u'archive_time': None,
 u'archive_url': u'/manage/events/archive/1113/',
 u'channels': [u'Main'],
 u'duplicate_url': u'/manage/events/duplicate/1113/',
 u'id': 1113,
 u'is_upcoming': True,
 u'location': u'Cyberspace - Pacific Time',
 u'modified': u'2014-08-06T22:04:11.727733+00:00',
 u'privacy': u'public',
 u'privacy_display': u'Public',
 u'slug': u'bugzilla-development-meeting-20141115',
 u'start_time': u'15 Nov 2014 02:00PM',
 u'start_time_iso': u'2014-11-15T14:00:00-08:00',
 u'status': u'scheduled',
 u'status_display': u'Scheduled',
 u'thumbnail': {u'height': 32,
                u'url': u'/media/cache/e7/1a/e71a58099a0b4cf1621ef3a9fe5ba121.png',
                u'width': 32},
 u'title': u'Bugzilla Development Meeting'}

So I thought one hackish simplification would be to convert each of these dicts into an list with a known sort order. Something like this:

>>> event = d['events'][0]
>>> pprint([event[k] for k in sorted(event)])
[None,
 u'/manage/events/archive/1113/',
 [u'Main'],
 u'/manage/events/duplicate/1113/',
 1113,
 True,
 u'Cyberspace - Pacific Time',
 u'2014-08-06T22:04:11.727733+00:00',
 u'public',
 u'Public',
 u'bugzilla-development-meeting-20141115',
 u'15 Nov 2014 02:00PM',
 u'2014-11-15T14:00:00-08:00',
 u'scheduled',
 u'Scheduled',
 {u'height': 32,
  u'url': u'/media/cache/e7/1a/e71a58099a0b4cf1621ef3a9fe5ba121.png',
  u'width': 32},
 u'Bugzilla Development Meeting']
 

So I converted my sample events.json file like that:

$ l -h events*
-rw-r--r--  1 peterbe  wheel   674K Aug  8 14:08 events.json
-rw-r--r--  1 peterbe  wheel   423K Aug  8 15:06 events.optimized.json

Excitingly the file is now 250Kb smaller because it no longer contains all those keys.

Now, I'd also send the order of the keys so I could do something like this in the AngularJS code:

 .success(function(response) {
   events = []
   response.events.forEach(function(event) {
     var new_event = {}
     response.keys.forEach(function(key, i) {
       new_event[k] = event[i]
     })
   })
 })
 

Yuck! Nested loops! It was just getting more and more complicated.
Also, if there are keys that are not present in every element, it means I'd have to replace them with None.

At this point I stopped and I could smell the hackish stink of sulfur of the hole I was digging myself into.
Then it occurred to me, gzip is really good at compressing repeated things which is something we have plenty of in a document store type data structure that a list of dicts is.

So I packed them manually to see what we could get:

$ apack events.json.gz events.json
$ apack events.optimized.json.gz events.optimized.json

And without further ado...

$ l -h events*
-rw-r--r--  1 peterbe  wheel   674K Aug  8 14:08 events.json
-rw-r--r--  1 peterbe  wheel    90K Aug  8 14:20 events.json.gz
-rw-r--r--  1 peterbe  wheel   423K Aug  8 15:06 events.optimized.json
-rw-r--r--  1 peterbe  wheel    81K Aug  8 15:07 events.optimized.json.gz

Basically, all that complicated and slow hoopla for saving 10Kb. No thank you.

Thank you gzip for existing!