empty array encoding compatibility with Sequel and ActiveRecord

[ermolaev]

Sequel

DB.fetch("SELECT ?", []).sql
=> "SELECT (NULL)"

ActiveRecord

Product.find_by_sql(['select ? ', []])
  Product Load (0.7ms)  select NULL

[ermolaev]

these are commonly used types, for performance, they should be placed on top

var = 2

Benchmark.ips do |r|
  r.report('bottom') do |n|
    while n > 0
      case var
      when String  then 1
      when Array   then 1
      when Symbol  then 1
      when Numeric then 1
      end
      n -= 1
    end
  end
  r.report('top') do |n|
    while n > 0
      case var
      when Numeric then 1
      when String  then 1
      when Array   then 1
      when Symbol  then 1
      end
      n -= 1
    end
  end
  r.compare!
end
# Comparison:
#                  top: 18495320.6 i/s
#               bottom:  5602695.7 i/s - 3.30x  slower

[SamSaffron]

Thanks @ermolaev ! change looks good to me