Module: Dnif::MultiAttribute

Defined in:
lib/dnif/multi_attribute.rb

Overview

Module MultiAttribute implements helpers to translate back and forth between Ruby Strings and an array of integers suitable for Sphinx attributes of type “multi”.

Background: Getting an ID as result for a query is OK, but for example to allow cast safety, we need an aditional attribute. Sphinx supports attributes which are returned together with the ID, but they behave a little different than expected: Instead we can use arrays of integers with ASCII character codes. These values are returned in ascending (!) order of value (yes, sounds funny but is reasonable from an internal view to Sphinx). So we mask each byte with 0x0100++ to keep the order…

Sample:

MongoSphinx::MultiAttribute.encode('Hello')
=> "328,613,876,1132,1391"
MongoSphinx::MultiAttribute.decode('328,613,876,1132,1391')
=> "Hello"

Class Method Summary collapse

Class Method Details

.decode(multi) ⇒ Object

Returns the original MongoDB ID created from a Sphinx ID. Only works if the ID was created from a MongoDB ID before!

Parameters:

multi

Sphinx “multi” attribute to translate back



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# File 'lib/dnif/multi_attribute.rb', line 45

def self.decode(multi)
  multi = multi.split(',') if not multi.is_a?(Array)

  offset = 0
  return multi.collect { |x| (x.to_i - (offset += 0x0100)).chr }.join("")
end

.encode(str) ⇒ Object

Returns an numeric representation of a Ruby String suitable for “multi” attributes of Sphinx.

Parameters:

str

String to translate



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# File 'lib/dnif/multi_attribute.rb', line 33

def self.encode(str)
  offset = 0
  return str.bytes.collect { |c| (offset+= 0x0100) + c }.join(',')
end