Performance

[lgebhardt]

A set of tweaks to reduce memory allocation in the worst spots. In general I've been trying to avoid premature optimizations, but I think in this case they are clear enough, and have enough benefit, to make it worth the minor added complexity.

Results from using the Peeps app with rack-mini-profiler:

gem 'rack-mini-profiler'
gem 'memory_profiler'

http://localhost:3000/contacts?include=phone-numbers&pp=profile-memory

Without:

Total allocated: 7562865 bytes (83291 objects)
Total retained:  543442 bytes (3826 objects)

allocated memory by gem
-----------------------------------
   2889655  jsonapi-resources/lib
   2001415  activesupport-5.2.3
    647682  activerecord-5.2.3
    561114  activemodel-5.2.3
    551528  set
    526434  json
    112432  bootsnap-1.4.4
     74306  sqlite3-1.4.1
     48232  tzinfo-1.2.5
     33544  arel-9.0.0
     29805  actionpack-5.2.3
     29399  digest
     23319  csv
      8973  rack-2.0.7
      6932  actionview-5.2.3
      4136  logger
      4104  concurrent-ruby-1.1.5
      3720  ipaddr
      2872  web-console-3.7.0
      1754  railties-5.2.3
       677  securerandom
       360  uri
       320  monitor
        72  mutex_m
        40  i18n-1.6.0
        40  rack-mini-profiler-1.0.2

And with this PR:

Total allocated: 6481135 bytes (71271 objects)
Total retained:  545970 bytes (3837 objects)

allocated memory by gem
-----------------------------------
   2001077  activesupport-5.2.3
   1808263  jsonapi-resources/lib
    647682  activerecord-5.2.3
    561114  activemodel-5.2.3
    551528  set
    526434  json
    112432  bootsnap-1.4.4
     74306  sqlite3-1.4.1
     48232  tzinfo-1.2.5
     33544  arel-9.0.0
     29805  actionpack-5.2.3
     29399  digest
     23319  csv
      8973  rack-2.0.7
      6932  actionview-5.2.3
      4136  logger
      4104  concurrent-ruby-1.1.5
      3720  ipaddr
      2872  web-console-3.7.0
      1754  railties-5.2.3
       677  securerandom
       360  uri
       320  monitor
        72  mutex_m
        40  i18n-1.6.0
        40  rack-mini-profiler-1.0.2

Timings run against a fresh development instance with no warm up show about a 6-7% improvement as well. The request is returning 50 primary and 100 related resources.

All Submissions:

• I've checked to ensure there aren't other open Pull Requests for the same update/change.
• I've submitted a ticket for my issue if one did not already exist.
• My submission passes all tests. (Please run the full test suite locally to cut down on noise from travis failures.)
• I've used Github auto-closing keywords in the commit message or the description.
• I've added/updated tests for this change.

New Feature Submissions:

• I've submitted an issue that describes this feature, and received the go ahead from the maintainers.
• My submission includes new tests.
• My submission maintains compliance with JSON:API.

Bug fixes and Changes to Core Features:

• I've included an explanation of what the changes do and why I'd like you to include them.
• I've provided test(s) that fails without the change.

Test Plan:

Reviewer Checklist:

• Maintains compliance with JSON:API
• Adequate test coverage exists to prevent regressions