Class: Ferret::Search::MultiPhraseQuery

Inherits:
Query
  • Object
show all
Includes:
Index
Defined in:
lib/ferret/search/multi_phrase_query.rb

Overview

MultiPhraseQuery is a generalized version of PhraseQuery, with an added method #add(Term[]).

To use this class, to search for the phrase “Microsoft app*” first use add(Term) on the term “Microsoft”, then find all terms that have “app” as prefix using IndexReader.terms(Term), and use MultiPhraseQuery.add(Term[] terms) to add them to the query.

Author Anders Nielsen

Defined Under Namespace

Classes: MultiPhraseWeight

Instance Attribute Summary collapse

Attributes inherited from Query

#boost

Instance Method Summary collapse

Methods inherited from Query

#combine, #extract_terms, #merge_boolean_queries, #similarity, #weight

Constructor Details

#initialize ⇒ MultiPhraseQuery

Returns a new instance of MultiPhraseQuery.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 17

def initialize()
  super()
  @slop = 0
  @term_arrays = []
  @positions = []
  @field = nil
end

Instance Attribute Details

#field ⇒ Object (readonly)

Returns the value of attribute field.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 15

def field
  @field
end

#positions ⇒ Object (readonly)

Returns the value of attribute positions.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 15

def positions
  @positions
end

#slop ⇒ Object

Returns the value of attribute slop.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 14

def slop
  @slop
end

#term_arrays ⇒ Object (readonly)

Returns the value of attribute term_arrays.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 15

def term_arrays
  @term_arrays
end

Instance Method Details

#add(terms, position = nil, pos_inc = 1) ⇒ Object Also known as: <<

Allows to specify the relative position of terms within the phrase.

See PhraseQuery#add(Term, int)

terms

the array of terms to search for or a single term

position

the position to search for these terms



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# File 'lib/ferret/search/multi_phrase_query.rb', line 30

def add(terms, position = nil, pos_inc = 1) 
  if position.nil?
    position = (@positions.size > 0) ? (@positions[-1] + pos_inc) : 0
  end

  if terms.instance_of?(Term)
    terms = [terms]
  end

  if (@term_arrays.size == 0)
    @field = terms[0].field
  end

  terms.each do |term|
    if (term.field != @field) 
      raise ArgumentError,
        "All phrase terms must be in the same field (#{@field}): #{term}"
    end
  end

  @term_arrays << terms
  @positions << position
end

#create_weight(searcher) ⇒ Object 



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# File 'lib/ferret/search/multi_phrase_query.rb', line 179

def create_weight(searcher)
  return MultiPhraseWeight.new(self, searcher)
end

#rewrite(reader) ⇒ Object 



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# File 'lib/ferret/search/multi_phrase_query.rb', line 165

def rewrite(reader) 
  if (@term_arrays.size() == 1) # optimize one-term case
    terms = @term_arrays[0]
    bq = BooleanQuery.new(true)
    terms.each do |term|
      bq.add(TermQuery.new(term), BooleanClause::Occur::SHOULD)
    end
    bq.boost = boost()
    return boq
  else 
    return self
  end
end

#to_s(f = nil) ⇒ Object

Prints a user-readable version of this query.



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# File 'lib/ferret/search/multi_phrase_query.rb', line 184

def to_s(f = nil) 
  buffer = ""
  buffer << "#{@field}:" if @field != f 
  buffer << '"'
  last_pos = -1
  @term_arrays.each_index do |i|
    terms = @term_arrays[i]
    pos = @positions[i]
    last_pos.upto(pos-2) {buffer << "<> "}
    last_pos = pos
    buffer << "#{terms.map {|term| term.text}.join("|")} "
  end
  buffer.rstrip!
  buffer << '"'

  buffer << "~#{@slop}" if (@slop != 0) 
  buffer << "^#{boost()}" if boost() != 1.0
  return buffer
end