nyastodon/app/models/keyword_mute.rb
David Yip 693c66dfde Use more idiomatic string concatentation. #164.
The intent of the previous concatenation was to minimize object
allocations, which can end up being a slow killer.  However, it turns
out that under MRI 2.4.x, the shove-strings-in-an-array-and-join method
is not only arguably more common but (in this particular case) actually
allocates *fewer* objects than the string concatenation.

Or, at least, that's what I gather by running this:

    words = %w(palmettoes nudged hibernation bullish stockade's tightened Hades
    Dixie's formalize superego's commissaries Zappa's viceroy's apothecaries
    tablespoonful's barons Chennai tollgate ticked expands)

    a = Account.first

    KeywordMute.transaction do
      words.each { |w| KeywordMute.create!(keyword: w, account: a) }

      GC.start

      s1 = GC.stat

      re = String.new.tap do |str|
        scoped = KeywordMute.where(account: a)
        keywords = scoped.select(:id, :keyword)
        count = scoped.count

        keywords.find_each.with_index do |kw, index|
          str << Regexp.escape(kw.keyword.strip)
          str << '|' if index < count - 1
        end
      end

      s2 = GC.stat

      puts s1.inspect, s2.inspect

      raise ActiveRecord::Rollback
    end

vs this:

    words = %w( palmettoes nudged hibernation bullish stockade's tightened Hades Dixie's
    formalize superego's commissaries Zappa's viceroy's apothecaries tablespoonful's
    barons Chennai tollgate ticked expands
    )

    a = Account.first

    KeywordMute.transaction do
      words.each { |w| KeywordMute.create!(keyword: w, account: a) }

      GC.start

      s1 = GC.stat

      re = [].tap do |arr|
        KeywordMute.where(account: a).select(:keyword, :id).find_each do |m|
          arr << Regexp.escape(m.keyword.strip)
        end
      end.join('|')

      s2 = GC.stat

      puts s1.inspect, s2.inspect

      raise ActiveRecord::Rollback
    end

Using rails r, here is a comparison of the total_allocated_objects and
malloc_increase_bytes GC stat data:

                 total_allocated_objects        malloc_increase_bytes
string concat    3200241 -> 3201428 (+1187)     1176 -> 45216 (44040)
array join       3200380 -> 3201299 (+919)      1176 -> 36448 (35272)
2017-10-21 14:54:36 -05:00

39 lines
926 B
Ruby

# frozen_string_literal: true
# == Schema Information
#
# Table name: keyword_mutes
#
# id :integer not null, primary key
# account_id :integer not null
# keyword :string not null
# created_at :datetime not null
# updated_at :datetime not null
#
class KeywordMute < ApplicationRecord
belongs_to :account, required: true
validates_presence_of :keyword
def self.matcher_for(account)
Rails.cache.fetch("keyword_mutes:matcher:#{account}") { Matcher.new(account) }
end
class Matcher
attr_reader :regex
def initialize(account)
re = [].tap do |arr|
KeywordMute.where(account: account).select(:keyword, :id).find_each do |m|
arr << Regexp.escape(m.keyword.strip)
end
end.join('|')
@regex = /\b(?:#{re})\b/i unless re.empty?
end
def =~(str)
regex ? regex =~ str : false
end
end
end