backgroundcompaction.rb

module Daybreak
  class BackgroundCompaction
    def initialize(file, options = {})
      @db = Daybreak::DB.new(file)
      @thread = Thread.new(&method(:run))
      @options = options
    end

    def stop
      @stop = true
      @thread.join
      @db.close
    end

    private

    def run
      until @stop
        @db.compact if compact_needed?
      end
    end

    def compact_needed?
      return true if @options[:force]
      @options[:ratio] ||= 2 # Two log records per table record
      @options[:reduction] ||= 4096 # One filesystem block, otherwise we won't gain
      logsize, bytesize, size = @db.logsize, @db.bytesize, @db.size
      logsize > @options[:ratio] * size || # Log size vs table size ratio
        bytesize - (bytesize * size / logsize) > @options[:reduction] # Estimate log size reduction
    end
  end
end