Ruby Incase Sensitive Sort

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Ruby has a .sort method which sorts basic objects. it is case sensitive though so Zebra is before apple. Using sort_by instead you can specify the sort key.

some_array.sort_by { |x| x.downcase }

There is a good description/discussion of the performance issues of this on ruby-docs

Since the ruby-docs mention performance issues I though it would be worth noting that in my blog app I have the option to pre sort with the ORM. this shouldmake the ruby sory much faster to execute as it is already mostly sorted, but how does this effect the performance of the ORM

def all_tags_sort
   @tags = Tags.find(:all, :order => "tag")
   @tags = @tags.sort_by { |tag| tag.tag.downcase }


def all_tags_sort
   @tags = Tags.find(:all)
   @tags = @tags.sort_by { |tag| tag.tag.downcase }

For the performance test I added this to one of views that displays the tags

#For Benchmarking
require 'benchmark'
include Benchmark

bm(10) do |b|"ORM") { @tags = Tags.find(:all) }"Sort by") { @tags = @tags.sort_by { |tag| tag.tag.downcase }  }"ORM sorted") { @tags = Tags.find(:all, :order => "tag") }"Sort by") { @tags = @tags.sort_by { |tag| tag.tag.downcase }  }

To test I built up a small dictionary using this gist (sorted by default so have to randomise it alittle bit)

                   user     system      total        real
ORM           53.920000   3.650000  57.570000 ( 57.960210)
Sort by        4.750000   0.320000   5.070000 (  5.091083)
ORM sorted    45.080000   3.590000  48.670000 ( 49.554891)
Sort by        2.700000   0.310000   3.010000 (  3.016042)

mmm, data does not look write as retrieving and sorting was quicker than just retrieving will run with the order swapped.

                user     system      total        real
ORM sorted 10.290000   1.740000  12.030000 ( 12.087005)
Sort by     0.930000   0.130000   1.060000 (  1.054450)
ORM        11.740000   1.700000  13.440000 ( 13.453623)
Sort by     0.760000   0.130000   0.890000 (  0.886095)

Sorting in the ORM layer still seems to be quicker than not sorting, and the Ruby sorting takes same length of time. So looks like applying the sort is a worthwhile.