Use MultiJson to improve JSON performance when possible

[ezkl]

This pull-request is a response to #99. It simply replaces OkJson w/ Intridea's MultiJson.

From the README:

MultiJSON tries to have intelligent defaulting. That is, if you have any of the supported engines already loaded, it will utilize them before attempting to load any. When loading, libraries are ordered by speed. First Oj, then Yajl, then the JSON gem, then JSON pure. If no other JSON library is available, MultiJSON falls back to OkJson, a simple, vendorable JSON parser.

As an example, to leverage the awesome Oj, add gem 'oj', '>= 1.3.5' to your app's Gemfile and bundle install. MultiJson will automatically use Oj for QC's JSON processing.

@ryandotsmith I didn't touch the tests. Would you like me to add one to assert that MultiJson is working properly?

[ryandotsmith]

@ezkl if you rebase this, I will merge and cut a new release.

[ryandotsmith]

What do you think of the json parser in ruby's stdlib? Would it be simpler to use it instead?

[arr-ee]

@ryandotsmith no it won't. MultiJson is pretty standard solution now, and the main point is that it can use different backends with no configuration (and degrades to stdlib parser or, in worst case, OkJson).
YAJL is faster than stdlib, OJ is faster than YAJL, some JRuby implementations might be faster than stdlib, so why not to give a choice?

If original author won't show up in foreseeable future and you don't want to rebase/add testcases, let me know, I'd be happy to do that.

Cheers, and thanks for this neat exploitation of Postgres' awesomeness!

[senny]

It's been quite some time since we had activity on this ticket. @arr-ee do you think you could take this one over?

[arr-ee]

Yeah, sure. Will try to push it this evening (i'm in UTC+8)

[senny]

@arr-ee ❤️

[ezkl]

Oof. Sorry for the delay. Must have missed the previous GH notifications.

[senny]

@ezkl thanks, do you think you could add that test-case? Also there are 4 commits attached, could you squash them into a single one so that we have all the changes together?

[senny]

I think we no longer have a dependency on scrolls is it necessary to introduce it again?

[senny]

@ezkl would be great if you could add the test-case. Also can you squash your commits together and push a rebased version?

[ezkl]

@senny I removed the old scrolls dependency, bumped multi_json, and squashed: a995f78

I'll gladly add a test. Do you have a particular concern w/r/t coverage?

[senny]

Thanks for the update!

If I'm not mistaken the current tests already exercise your code path. If that's the case I think we don't need an extra test-case.

[ryandotsmith]

👍

[senny]

@ezkl thanks!

[nashbridges]

Readme still mentions OkJson.

[senny]

@nashbridges thanks for the hint. I updated the README: f251345