Use nested hashes instead of string keys

[NickLaMuro]

For both instantiating the values, and retrieving the data, using string based keys requires a bunch of new object allocations for something that is simply used for a faster lookup for data already put into the XML structure (I think...), by using a nested hash structure, we can keep the same "lookup" functionality, but not require the extra allocations to do so.

As far as I can tell, the only place this lookup is used is in one method, so this should be okay to change.

Benchmarks

The benchmark script used here basically runs the following:

ManageIQ::Providers::Vmware::InfraManager::ProvisionWorkflow.new.init_from_dialog

And is targeting a fairly large EMS, with about 600 hosts.

	ms	queries	rows
before	15023	1961	48395
after	13753	1961	48395

Before                                                     After
------                                                     -----

Total allocated: 2069091751 bytes (23226536 objects)   |   Total allocated: 1970420998 bytes (21117758 objects)
                                                       |   
allocated objects by gem                               |   allocated objects by gem
-----------------------------------                    |   -----------------------------------
   9665227  pending                                    |      9665227  pending
   5561668  manageiq/app  <<<<<<<<<<                   |      4155069  manageiq/app  <<<<<<<<<<
   3513258  manageiq/lib                               |      3513258  manageiq/lib
   2512007  activerecord-5.0.7                         |      2512007  activerecord-5.0.7
    861270  activesupport-5.0.7  <<<<<<<<<<            |       418737  ancestry-2.2.2
    418737  ancestry-2.2.2                             |       278793  activemodel-5.0.7
    278793  activemodel-5.0.7                          |       178419  ruby-2.3.3/lib
    178419  ruby-2.3.3/lib                             |       165577  arel-7.1.4
    165577  arel-7.1.4                                 |       159091  activesupport-5.0.7  <<<<<<<<<<
     52875  manageiq-providers-vmware-0be2f13a0dc9     |        52875  manageiq-providers-vmware-0be2f13a0dc9
     14424  fast_gettext-1.2.0                         |        14424  fast_gettext-1.2.0
       ...                                             |          ...

Note: The benchmarks for this change do NOT include the changes from other PRs (#17354 for example). Benchmarks of all changes can be found here.

Links

• Partially addresses https://bugzilla.redhat.com/show_bug.cgi?id=1569626
• Full collection of proposed changes: git compare
• Document keeping track of overall improvements for this effort: gist
• Related PRs:
  • Prevents N+1 SQL queries in miq_request_workflow.rb #17354
    • Extracted PRs: Add MiqPreloader.polymorphic_preload_for_child_classes #17457, Use MiqPreloader.polymorphic_preload_for_child_classes in RelationshipMixin#fulltree_arranged #17460, Use MiqPreloader/Relationship improvements in MiqRequestWorkflow #17461
  • Memoize _log.prefix calls #17355
  • Refactor get_ems_folders to create less strings #17358
  • Use OpenStruct over MiqHashStruct #17359
  • Ancestry Patches #17360
  • Load Lans effeciently in MiqProvisionVirtWorkflow #17381
  • Avoid duplicate host load in allowed_hosts_obj #17402
  • [WIP] Lighter unique Host#domain lookup for in MiqProvisionVirtWorkflow #17403

[miq-bot]

Checked commit NickLaMuro@ef73d6e with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
2 files checked, 0 offenses detected
Everything looks fine. 🍪

[NickLaMuro]

@miq-bot assign @gmcculloug
@miq-bot add_label performance

[syncrou]

@NickLaMuro - This looks good to me.

[NickLaMuro]

@miq-bot add_label fine/yes, gaprindashvili/yes

[simaishi]

Fine backport details:

$ git log -1
commit 831c6435387ec9b5d69355523d3c80df31c0f218
Author: Keenan Brock <[email protected]>
Date:   Fri May 18 12:21:35 2018 -0400

    Merge pull request #17357 from NickLaMuro/nested_hashes_for_miq_request_workflow
    
    Use nested hashes instead of string keys
    (cherry picked from commit 5f22e971f034528138b6be42181ee4ba90461fdb)
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1593798

[simaishi]

Gaprindashvili backport details:

$ git log -1
commit de6d40d4967862e0ea4d673fe8efea255b6d4f19
Author: Keenan Brock <[email protected]>
Date:   Fri May 18 12:21:35 2018 -0400

    Merge pull request #17357 from NickLaMuro/nested_hashes_for_miq_request_workflow
    
    Use nested hashes instead of string keys
    (cherry picked from commit 5f22e971f034528138b6be42181ee4ba90461fdb)
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1593797