class PgSearch::Features::TSearch

The integer option controls several behaviors, so it is a bit mask: you can specify one or more behaviors
32 divides the rank by itself + 1
16 divides the rank by 1 + the logarithm of the number of unique words in document
8 divides the rank by the number of unique words in document
4 divides the rank by the mean harmonic distance between extents (this is implemented only by ts_rank_cd)
2 divides the rank by the document length
1 divides the rank by 1 + the logarithm of the document length
0 (the default) ignores the document length
From http://www.postgresql.org/docs/8.3/static/textsearch-controls.html

def normalization
  @options[:normalization] || 0
end