Class | Ferret::Index::FieldInfo
In: | ext/r_index.c
Parent: | Object

## Summary

The FieldInfo class is the field descriptor for the index. It specifies whether a field is compressed or not or whether it should be indexed and tokenized. Every field has a name which must be a symbol. There are three properties that you can set, +:store+, +:index+ and +:term_vector+. You can also set the default +:boost+ for a field as well.

## Properties

### :store

The +:store+ property allows you to specify how a field is stored. You can leave a field unstored (+:no+), store it in it‘s original format (+:yes+) or store it in compressed format (+:compressed+). By default the document is stored in its original format. If the field is large and it is stored elsewhere where it is easily accessible you might want to leave it unstored. This will keep the index size a lot smaller and make the indexing process a lot faster. For example, you should probably leave the +:content+ field unstored when indexing all the documents in your file-system.

### :index

The +:index+ property allows you to specify how a field is indexed. A field must be indexed to be searchable. However, a field doesn‘t need to be indexed to be store in the Ferret index. You may want to use the index as a simple database and store things like images or MP3s in the index. By default each field is indexed and tokenized (split into tokens) (+:yes+). If you don‘t want to index the field use +:no+. If you want the field indexed but not tokenized, use +:untokenized+. Do this for the fields you wish to sort by. There are two other values for +:index+; +:omit_norms+ and +:untokenized_omit_norms+. These values correspond to +:yes+ and +:untokenized+ respectively and are useful if you are not boosting any fields and you‘d like to speed up the index. The norms file is the file which contains the boost values for each document for a particular field.

### :term_vector

See TermVector for a description of term-vectors. You can specify whether or not you would like to store term-vectors. The available options are +:no+, +:yes+, +:with_positions+, +:with_offsets+ and +:with_positions_offsets+. Note that you need to store the positions to associate offsets with individual terms in the term_vector.

## Property Table

      Property       Value                     Description
      ------------------------------------------------------------------------
       :store       | :no                     | Don't store field
                    |                         |
                    | :yes (default)          | Store field in its original
                    |                         | format. Use this value if you
                    |                         | want to highlight matches.
                    |                         | or print match excerpts a la
                    |                         | Google search.
                    |                         |
                    | :compressed             | Store field in compressed
                    |                         | format.
       -------------|-------------------------|------------------------------
       :index       | :no                     | Do not make this field
                    |                         | searchable.
                    |                         |
                    | :yes (default)          | Make this field searchable and
                    |                         | tokenized its contents.
                    |                         |
                    | :untokenized            | Make this field searchable but
                    |                         | do not tokenize its contents.
                    |                         | use this value for fields you
                    |                         | wish to sort by.
                    |                         |
                    | :omit_norms             | Same as :yes except omit the
                    |                         | norms file. The norms file can
                    |                         | be omitted if you don't boost
                    |                         | any fields and you don't need
                    |                         | scoring based on field length.
                    |                         |
                    | :untokenized_omit_norms | Same as :untokenized except omit
                    |                         | the norms file. Norms files can
                    |                         | be omitted if you don't boost
                    |                         | any fields and you don't need
                    |                         | scoring based on field length.
                    |                         |
       -------------|-------------------------|------------------------------
       :term_vector | :no                     | Don't store term-vectors
                    |                         |
                    | :yes                    | Store term-vectors without
                    |                         | storing positions or offsets.
                    |                         |
                    | :with_positions         | Store term-vectors with
                    |                         | positions.
                    |                         |
                    | :with_offsets           | Store term-vectors with
                    |                         | offsets.
                    |                         |
                    | :with_positions_offsets | Store term-vectors with
                    | (default)               | positions and offsets.
       -------------|-------------------------|------------------------------
       :boost       | Float                   | The boost property is used to
                    |                         | set the default boost for a
                    |                         | field. This boost value will
                    |                         | used for all instances of the
                    |                         | field in the index unless
                    |                         | otherwise specified when you
                    |                         | create the field. All values
                    |                         | should be positive.
                    |                         |

## Examples

      fi = FieldInfo.new(:title, :index => :untokenized, :term_vector => :no,
                         :boost => 10.0)

      fi = FieldInfo.new(:content)

      fi = FieldInfo.new(:created_on, :index => :untokenized_omit_norms,
                         :term_vector => :no)

      fi = FieldInfo.new(:image, :store => :compressed, :index => :no,
                         :term_vector => :no)

### Methods

boost compressed? has_norms? indexed? name new omit_norms? store_offsets? store_positions? store_term_vector? stored? to_s tokenized?

### Public Class methods

FieldInfo.new(name, options = {}) → field_info

Create a new FieldInfo object with the name `name` and the properties specified in `options`. The available options are [:store, :index, :term_vector, :boost]. See the description of FieldInfo for more information on these properties.

### Public Instance methods

fi.boost → boost

Return the default boost for this field

fi.compressed? → bool

Return true if the field is stored in the index in compressed format.

fi.has_norms? → bool

Return true if this field has a norms file. This is the same as calling;

      fi.indexed? and not fi.omit_norms?

fi.indexed? → bool

Return true if the field is indexed, ie searchable in the index.

fi.name → symbol

Return the name of the field

fi.omit_norms? → bool

Return true if the field omits the norm file. The norm file is the file used to store the field boosts for an indexed field. If you do not boost any fields, and you can live without scoring based on field length then you can omit the norms file. This will give the index a slight performance boost and it will use less memory, especially for indexes which have a large number of documents.

fi.store_offsets? → bool

Return true if offsets are stored with the term-vectors for this field.

fi.store_positions? → bool

Return true if positions are stored with the term-vectors for this field.

fi.store_term_vector? → bool

Return true if the term-vectors are stored for this field.

fi.stored? → bool

Return true if the field is stored in the index.

fi.to_s → string

Return a string representation of the FieldInfo object.

fi.tokenized? → bool

Return true if the field is tokenized. Tokenizing is the process of breaking the field up into tokens. That is "the quick brown fox" becomes:

      ["the", "quick", "brown", "fox"]

A field can only be tokenized if it is indexed.

[Validate]