Ruby on Rails Knowledge Patch Skill

Ruby on Rails Knowledge Patch

Covers Rails 8.0–8.1 changes. Training cutoff: Rails 7.1, Ruby 3.3.

Index

| Topic | Reference | Key features | |---|---|---| | Rails 8.0 architecture | references/rails-8-architecture.md | Solid Queue/Cache/Cable, Kamal 2, Propshaft, auth generator, Turbo morphing | | Active Record queries & schema | references/active-record-queries.md | params.expect, pluck hash, UPDATE with JOIN, first/last deprecation, schema sorting | | Active Record columns & serialization | references/active-record-columns.md | only_columns, update_column touch, serialized comparable, JSON coder, PG 18 virtual columns | | Database configuration | references/database-config.md | Connection pool options, transaction isolation, SQLite extensions, invisible indexes | | Active Job continuations | references/active-job-continuations.md | Resumable multi-step jobs with cursor tracking | | Tooling & framework | references/tooling.md | Local CI, credentials:fetch, structured events, markdown rendering, deprecated associations | | Deprecations & removals | references/deprecations.md | sidekiq adapter, ActiveSupport::Configurable, mb_chars, Active Storage Azure |

Rails 8.0 — No Redis, No Sprockets, No Traefik

Rails 8.0 removes external dependencies:

Solid Queue replaces Sidekiq/Resque as default Active Job backend (database-backed, FOR UPDATE SKIP LOCKED)
Solid Cache replaces Redis/Memcached for fragment caching
Solid Cable replaces Redis for Action Cable pub/sub
Propshaft replaces Sprockets (digest stamping only, no transpilation)
Kamal 2 replaces Capistrano/manual deployment (with kamal-proxy instead of Traefik)
Authentication generator (rails generate authentication) — session-based, password-resettable
Turbo 8 morphing — turbo_refreshes_with method: :morph, scroll: :preserve for DOM morphing
allow_browser guard — allow_browser versions: :modern returns 406 for old browsers
Thruster — HTTP/2 proxy in Dockerfile for asset caching/compression

See references/rails-8-architecture.md for full details, configuration, and code examples.

Quick Reference

params.expect replaces require/permit (8.0)

# New preferred way (safer, more explicit)
params.expect(post: [:title, :body])
# replaces: params.require(:post).permit(:title, :body)

SQLite virtual tables (8.0)

create_virtual_table :posts_search, :fts5, ["content", "title"]

Custom batch columns (8.0)

Product.in_batches(cursor: [:shop_id, :id]) do |relation|
  # batches using composite cursor
end

Pluck with hash for joined tables (8.0)

Post.joins(:comments).pluck(:id, comments: :id)

db:migrate on fresh database (8.0)

db:migrate on a fresh database now loads the schema first, then runs only pending migrations. Use db:migrate:reset for the old behavior.

Active Job Continuations (8.1)

Long-running jobs broken into resumable steps via ActiveJob::Continuable:

class ProcessImportJob < ApplicationJob
  include ActiveJob::Continuable

  def perform(import_id)
    step :validate do
      # runs once
    end

    step :process do |step|
      Record.find_each(start: step.cursor) do |record|
        record.process
        step.advance! from: record.id
      end
    end

    step :finalize  # calls private method
  end
end

Structured Event Reporting (8.1)

Rails.event.notify("user.signup", user_id: 123, email: "user@example.com")
Rails.event.tagged("graphql") { Rails.event.notify("query.executed", duration: 42) }
Rails.event.set_context(request_id: "abc123", shop_id: 456)

Connection pool configuration (8.1)

production:
  adapter: postgresql
  max_connections: 10 # renamed from pool (old name still works)
  min_connections: 2
  keepalive: 300
  max_age: 600

Transaction isolation (8.1)

ActiveRecord.with_transaction_isolation_level(:read_committed) do
  Tag.create!  # uses read_committed isolation
end
# Also: connection.current_transaction.isolation

Deprecated associations (8.1)

has_many :posts, deprecated: true                       # warn mode (default)
has_many :posts, deprecated: { mode: :raise }           # or :notify
has_many :posts, deprecated: { mode: :warn, backtrace: true }

Reports all usage: author.posts, author.preload(:posts), nested attributes, etc.

only_columns — inverse of ignored_columns (8.1)

class User < ApplicationRecord
  self.only_columns = %w[id name email]
end

UPDATE with JOIN — PostgreSQL & SQLite3 (8.1)

Comment.joins(:post).update_all("title = posts.title")

Previously MySQL-only. Now works for PostgreSQL and SQLite3 (without LIMIT/ORDER/GROUP BY).

Local CI (8.1)

# config/ci.rb — run with bin/ci
CI.run do
  step "Setup", "bin/setup --skip-server"
  step "Style: Ruby", "bin/rubocop"
  step "Tests: Rails", "bin/rails test"

  if success?
    step "Signoff", "gh signoff"
  else
    failure "CI failed.", "Fix the issues and try again."
  end
end

credentials:fetch command (8.1)

rails credentials:fetch kamal.registry_password
# Useful in .kamal/secrets:
# KAMAL_REGISTRY_PASSWORD=$(rails credentials:fetch kamal.registry_password)

update_column with touch (8.1)

user.update_column(:nice, true, touch: true)        # also updates updated_at
user.update_columns(last_ip: request.remote_ip, touch: true)

Serialized comparable attributes (8.1)

serialize :config, type: Hash, coder: JSON, comparable: true  # avoids false dirty tracking

SQLite extensions in database.yml (8.1)

development:
  adapter: sqlite3
  extensions:
    - SQLean::UUID # module responding to .to_path
    - .sqlpkg/nalgeon/crypto/crypto.so # filesystem path

PG 18 virtual generated columns (8.1)

create_table :users do |t|
  t.string :name
  t.virtual :lower_name, type: :string, as: "LOWER(name)"          # virtual on PG 18+
  t.virtual :name_length, type: :integer, as: "LENGTH(name)", stored: true
end

first/last without order deprecated (8.1)

# config/application.rb (Rails 8.1 default)
config.active_record.raise_on_missing_required_finder_order_columns = true

Raises ActiveRecord::MissingRequiredOrderError if no order, implicit_order_column, query_constraints, or primary_key.

New exception classes (8.1)

ActiveRecord::CheckViolation — check constraint violations
ActiveRecord::ExclusionViolation — PostgreSQL exclusion constraint violations

Key changes summary

| Feature | Version | Area | |---------|---------|------| | Solid Queue/Cache/Cable defaults | 8.0 | Infrastructure | | Kamal 2 deployment | 8.0 | Deployment | | Propshaft asset pipeline | 8.0 | Assets | | Authentication generator | 8.0 | Security | | Turbo 8 morphing | 8.0 | Hotwire | | allow_browser guard | 8.0 | Security | | params.expect | 8.0 | Controllers | | SQLite virtual tables | 8.0 | Active Record | | Custom batch cursors | 8.0 | Active Record | | Pluck with hash | 8.0 | Active Record | | db:migrate loads schema first | 8.0 | Migrations | | Job continuations | 8.1 | Active Job | | Structured events | 8.1 | Framework | | Local CI (bin/ci) | 8.1 | Tooling | | Markdown rendering | 8.1 | Action View | | credentials:fetch | 8.1 | Tooling | | Deprecated associations | 8.1 | Active Record | | only_columns | 8.1 | Active Record | | update_column touch | 8.1 | Active Record | | Connection pool config | 8.1 | Database | | Transaction isolation | 8.1 | Active Record | | Serialized comparable | 8.1 | Active Record | | JSON coder options | 8.1 | Active Record | | SQLite extensions in YAML | 8.1 | Database | | Invisible indexes | 8.1 | MySQL/MariaDB | | first/last without order deprecated | 8.1 | Active Record | | UPDATE with JOIN (PG/SQLite) | 8.1 | Active Record | | PG 18 virtual generated columns | 8.1 | PostgreSQL | | Schema columns sorted | 8.1 | Migrations | | New exception classes | 8.1 | Active Record |

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