Class: Ferret::Search::FieldCache

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

Overview

Expert: The default cache implementation, storing all values in memory. A WeakKeyHash is used for storage.

Defined Under Namespace

Classes: Entry, StringIndex

Constant Summary collapse

INT_PARSER = 
lambda {|i| i.to_i}
FLOAT_PARSER = 
lambda {|i| i.to_f}
@@cache =

The internal cache. Maps Entry to array of interpreted term values.

Ferret::Utils::WeakKeyHash.new

Class Method Summary collapse

Class Method Details

.get_auto_index(reader, field) ⇒ Object

Checks the internal cache for an appropriate entry, and if none is found reads field to see if it contains integers, floats or strings, and then calls one of the other methods in this class to get the values. For string values, a StringIndex is returned. After calling this method, there is an entry in the cache for both type AUTO and the actual found type.

reader

Used to get field values.

field

Which field contains the values.

return

Integer Array, Float Array or StringIndex.



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# File 'lib/ferret/search/field_cache.rb', line 182

def FieldCache.get_auto_index(reader, field)
  index = lookup(reader, field, SortField::SortType::AUTO)
  if (index == nil) 
    term_enum = reader.terms_from(Term.new(field, ""))
    begin 
      term = term_enum.term
      if (term == nil) 
        raise "no terms in field #{field} to sort by"
      end
      if (term.field == field) 
        termtext = term.text.strip

        if (termtext == termtext.to_i.to_s)
          index = get_index(reader, field, SortField::SortType::INTEGER)
        elsif (termtext == termtext.to_f.to_s or termtext == "%f"%termtext.to_f)
          index = get_index(reader, field, SortField::SortType::FLOAT)
        else
          index = get_string_index(reader, field)
        end

        if (index != nil) 
          store(reader, field, SortField::SortType::AUTO, index)
        end
      else 
        raise "field \"#{field}\" does not appear to be indexed"
      end
    ensure 
      term_enum.close()
    end
  end
  return index
end

.get_index(reader, field, sort_type) ⇒ Object

Checks the internal cache for an appropriate entry, and if none is found, reads the terms in field and parses them with the provided parser and returns an array of size reader.max_doc of the value each document has in the given field.

reader

Used to get field values.

field

Which field contains the values.

sort_type

The type of sort to run on the field. Holds the parser

return

The values in the given field for each document.



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# File 'lib/ferret/search/field_cache.rb', line 72

def FieldCache.get_index(reader, field, sort_type)
  index = lookup(reader, field, sort_type)
  if (index == nil) 
    parser = sort_type.parser
    index = Array.new(reader.max_doc)
    if (index.length > 0) 
      term_docs = reader.term_docs
      term_enum = reader.terms_from(Term.new(field, ""))
      begin 
        if term_enum.term.nil? 
          raise "no terms in field '#{field}' to sort by"
        end
        begin 
          term = term_enum.term
          break if (term.field != field)
          termval = parser.call(term.text)
          term_docs.seek(term)
          while term_docs.next? 
            index[term_docs.doc] = termval
          end
        end while term_enum.next?
      ensure 
        term_docs.close()
        term_enum.close()
      end
    end
    store(reader, field, sort_type, index)
  end
  return index
end

.get_string_index(reader, field) ⇒ Object

Checks the internal cache for an appropriate entry, and if none is found reads the term values in field and returns an array of them in natural order, along with an array telling which element in the term array each document uses.

reader

Used to get field values.

field

Which field contains the strings.

returns

Array of terms and index into the array for each document.



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# File 'lib/ferret/search/field_cache.rb', line 111

def FieldCache.get_string_index(reader, field)
  index = lookup(reader, field, SortField::SortType::STRING)
  if (index == nil) 
    str_index = Array.new(reader.max_doc)
    str_map = Array.new(reader.max_doc+1)
    if (str_index.length > 0) 
      term_docs = reader.term_docs
      term_enum = reader.terms_from(Term.new(field,""))
      t = 0 # current term number


      # an entry for documents that have no terms in this field should a

      # document with no terms be at top or bottom?

      #

      # this puts them at the top - if it is changed, FieldDocSortedHitQueue

      # needs to change as well.

      str_map[t] = nil
      t += 1

      begin 
        if (term_enum.term() == nil) 
          raise "no terms in field #{field} to sort by"
        end
        begin
          term = term_enum.term
          break if (term.field != field)

          # store term text

          # we expect that there is at most one term per document

          if (t >= str_map.length)
            raise "there are more terms than documents in field \"#{field}\", but it's impossible to sort on tokenized fields"
          end
          str_map[t] = term.text

          term_docs.seek(term)
          while term_docs.next?
            str_index[term_docs.doc] = t
          end

          t += 1
        end while term_enum.next?
      ensure 
        term_docs.close()
        term_enum.close()
      end

      if (t == 0) 
        # if there are no terms, make the term array

        # have a single nil entry

        # str_map = [nil] <= already set above

      elsif (t < str_map.length) 
        # if there are less terms than documents,

        # trim off the dead array space

        str_map.compact!
      end
    end
    index = StringIndex.new(str_index, str_map)
    store(reader, field, SortField::SortType::STRING, index)
  end
  return index
end

.lookup(reader, field, sort_type) ⇒ Object

See if an object is in the cache.



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# File 'lib/ferret/search/field_cache.rb', line 41

def FieldCache.lookup(reader, field, sort_type) 
  entry = Entry.new(field, sort_type)
  @@cache.synchronize() do
    reader_cache = @@cache[reader]
    return nil if reader_cache.nil?
    return reader_cache[entry]
  end
end

.store(reader, field, sort_type, value) ⇒ Object

Put an object into the cache.



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# File 'lib/ferret/search/field_cache.rb', line 51

def FieldCache.store(reader, field, sort_type, value) 
  entry = Entry.new(field, sort_type)
  @@cache.synchronize() do
    reader_cache = @@cache[reader]
    if (reader_cache == nil) 
      reader_cache = {}
      @@cache[reader] = reader_cache
    end
    return reader_cache[entry] = value
  end
end