Reproduces https://github.com/rsim/oracle-enhanced/issues/1720 (comparison with MySQL)

oracle_enhanced_1720_mysql.rb

# frozen_string_literal: true

# This file attempts to reproduce issue #1720 of the enhanced adapter
# (https://github.com/rsim/oracle-enhanced). See issue comments for instructions
# on how to use this file.

# CONFIGURATION

DB_CONFIG = {
  adapter: :mysql2,
  host: 'REPLACE_ME' || ENV['DB_HOST'],
  port: REPLACE_ME || ENV['DB_PORT'],
  database: 'REPLACE_ME' || ENV['DB_NAME'],
  username: 'REPLACE_ME' || ENV['DB_USERNAME'],
  password: 'REPLACE_ME' || ENV['DB_PASSWORD']
}.freeze

# END OF CONFIGURATION

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'activerecord', ENV['NEW'] ? '5.2.0' : '5.1.6'
  gem 'activerecord-jdbcmysql-adapter'
  gem 'pry'
end

require 'active_record'
require 'minitest/autorun'
require 'active_record/connection_adapters/jdbcmysql_adapter'
require "logger"

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(DB_CONFIG)
ActiveRecord::Base.logger = Logger.new(STDOUT)

TABLE_COUNT = 20
COLUMN_COUNT_PER_TYPE = 10

ActiveRecord::Schema.define do
  TABLE_COUNT.times do |i|
    create_table :"table_#{i}", force: true do |t|
      COLUMN_COUNT_PER_TYPE.times do |j|
        t.string :"string_column_#{j}"
        t.integer :"integer_column_#{j}"
      end
    end
  end
end

class BugTest < Minitest::Test
  # Tries to reproduce #1070. Works as expected.
  def test_performance
    benchmark = Benchmark.measure {
      TABLE_COUNT.times do |i|
        c = Class.new(ActiveRecord::Base) do
          self.table_name = "table_#{i}"
        end
        c.first
      end
    }

    puts "BENCHMARK:"
    puts benchmark
  end
end