Class: RenderGuardian::NPlusOneDetector

Inherits:
Object
  • Object
show all
Defined in:
lib/render_guardian/n_plus_one_detector.rb

Instance Method Summary collapse

Constructor Details

#initialize(profiler) ⇒ NPlusOneDetector

Returns a new instance of NPlusOneDetector.



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# File 'lib/render_guardian/n_plus_one_detector.rb', line 5

def initialize(profiler)
  @profiler = profiler
end

Instance Method Details

#detect ⇒ Object 



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# File 'lib/render_guardian/n_plus_one_detector.rb', line 9

def detect
  findings = []
  threshold = @profiler.budget.limit_for(:n_plus_one_threshold)

  # Check per-partial query counts
  @profiler.stats_by_partial.each do |partial, stats|
    if stats[:total_queries] / stats[:count] > @profiler.budget.limit_for(:max_db_queries_per_partial)
      findings << {
        type:           :n_plus_one_suspected,
        severity:       :high,
        partial:        partial,
        avg_queries:    (stats[:total_queries].to_f / stats[:count]).round(2),
        threshold:      @profiler.budget.limit_for(:max_db_queries_per_partial),
        render_count:   stats[:count],
        message:        "Partial '#{partial}' averages #{(stats[:total_queries].to_f / stats[:count]).round(2)} DB queries per render (threshold: #{@profiler.budget.limit_for(:max_db_queries_per_partial)})"
      }
    end
  end

  # Detect repeated identical queries across events (classic N+1 pattern)
  query_counts = Hash.new(0)
  @profiler.events.each do |event|
    event.db_queries.each { |q| query_counts[q] += 1 }
  end

  query_counts.select { |_, count| count >= threshold }.each do |query, count|
    findings << {
      type:     :repeated_query,
      severity: :high,
      query:    query,
      count:    count,
      message:  "Query executed #{count} times across renders — possible N+1: '#{query[0..80]}'"
    }
  end

  findings
end