TICKET-599: Use pluck and remove unnecessary ActiveRecord object instantiations

[Naragod]

Proposed Changes

🐛 Bug fix replace to_json with pluck and prevent unnecessary ActiveRecord object instantiations from being created in memory.

The original code was:

1. SELECT * FROM users -> 14 columns from DB
2. Build 14,565 User objects -> Ruby heap allocations, callbacks
3. to_json(only: 7_fields) -> serialize, discard 7 columns

visible_users.order(:created_at).to_json(only: DEFAULT_FIELDS)

The new code is:

1. SELECT id, user_name, ... FROM users -> 7 columns from DB
2. Returns arrays of raw values -> no objects, no callbacks
3. Zip into hashes, serialize to JSON

rows = visible_users.order(:created_at).pluck(*DEFAULT_FIELDS)
rows.map { |r| DEFAULT_FIELDS.zip(r).to_h }

Screenshots of your changes (if applicable)

Associated documentation repository pull request (if applicable)

Type of Change

(Write an X or a brief description next to the type or types that best describe your changes.)

Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)	X
🎨 User interface change (change to user interface; provide screenshots)
♻️ Refactoring (internal change to codebase, without changing functionality)
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

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Questions and Comments

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[coveralls]

Coverage Report for CI Build 24058740316

Coverage increased (+0.001%) to 91.71%

Details

• Coverage increased (+0.001%) from the base build.
• Patch coverage: 6 of 6 lines across 2 files are fully covered (100%).
• 11 coverage regressions across 1 file.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

11 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
app/controllers/api/users_controller.rb	11	78.33%

---

Coverage Stats

Relevant Lines:	48456
Covered Lines:	45180
Line Coverage:	93.24%
Relevant Branches:	1844
Covered Branches:	950
Branch Coverage:	51.52%
Branches in Coverage %:	Yes
Coverage Strength:	130.71 hits per line

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💛 - Coveralls

[donny-wong]

Very good @Naragod !