Class: Ferret::Analysis::Analyzer

Inherits:
Object
  • Object
show all
Defined in:
lib/ferret/analysis/analyzers.rb

Overview

An Analyzer builds TokenStreams, which analyze text. It thus represents a policy for extracting index terms from text.

Typical implementations first build a Tokenizer, which breaks the stream of characters from the Reader into raw Tokens. One or more TokenFilter s may then be applied to the output of the Tokenizer.

The default Analyzer just creates a LowerCaseTokenizer which converts all text to lowercase tokens. See LowerCaseTokenizer for more details.

Instance Method Summary collapse

Instance Method Details

#position_increment_gap(field_name) ⇒ Object

Invoked before indexing a Field instance if terms have already been added to that field. This allows custom analyzers to place an automatic position increment gap between Field instances using the same field name. The default value position increment gap is 0. With a 0 position increment gap and the typical default token position increment of 1, all terms in a field, including across Field instances, are in successive positions, allowing exact PhraseQuery matches, for instance, across Field instance boundaries.

field_name

Field name being indexed.

position_increment_gap

added to the next token emitted from #token_stream(String,Reader)



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# File 'lib/ferret/analysis/analyzers.rb', line 34

def position_increment_gap(field_name)
  return 0
end

#token_stream(field, string) ⇒ Object

Creates a TokenStream which tokenizes all the text in the provided Reader. Override to allow Analyzer to choose strategy based on document and/or field.

string

the string representing the text in the field

field

name of the field. Not required.



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# File 'lib/ferret/analysis/analyzers.rb', line 17

def token_stream(field, string)
  return LowerCaseTokenizer.new(string)
end