Class | Ferret::Index::Index
In: | lib/ferret/index.rb
Parent: | Object

This is a simplified interface to the index. See the TUTORIAL for more information on how to use this class.

### Methods

<< [] add_document add_indexes close commit delete deleted? doc ensure_reader_open ensure_searcher_open ensure_writer_open explain field_infos flush has_deletions? highlight new optimize persist process_query query_delete query_update reader search search_each searcher size to_s update writer

### Included Modules

MonitorMixin Ferret::Store Ferret::Search

### Attributes

options | [R] |

### Public Class methods

new(options = {}) {|self| ...}

If you create an Index without any options, it‘ll simply create an index in memory. But this class is highly configurable and every option that you can supply to IndexWriter and QueryParser, you can also set here. Please look at the options for the constructors to these classes.

### Options

See;

- QueryParser
- IndexWriter

default_input_field: | Default: "id". This specifies the default field that will be used when you add a simple string to the index using add_document or <<.

id_field: Default: "id". This field is as the field to

                            search when doing searches on a term. For
                            example, if you do a lookup by term "cat", ie
                            index["cat"], this will be the field that is
                            searched.

key:

Default: nil. Expert: This should only be used if you really know what you are doing. Basically you can set a field or an array of fields to be the key for the index. So if you add a document with a same key as an existing document, the existing document will be replaced by the new object. Using a multiple field key will slow down indexing so it should not be done if performance is a concern. A single field key (or id) should be find however. Also, you must make sure that your key/keys are either untokenized or that they are not broken up by the analyzer.

auto_flush:

Default: false. Set this option to true if you want the index automatically flushed every time you do a write (includes delete) to the index. This is useful if you have multiple processes accessing the index and you don‘t want lock errors. Setting :auto_flush to true has a huge performance impact so don‘t use it if you are concerned about performance. In that case you should think about setting up a DRb indexing service.

lock_retry_time: | Default: 2 seconds. This parameter specifies how long to wait before retrying to obtain the commit lock when detecting if the IndexReader is at the latest version.
close_dir: | Default: false. If you explicitly pass a Directory object to this class and you want Index to close it when it is closed itself then set this to true.

Some examples;

      index = Index::Index.new(:analyzer => WhiteSpaceAnalyzer.new())

      index = Index::Index.new(:path => '/path/to/index',
                               :create_if_missing => false,
                               :auto_flush => true)

      index = Index::Index.new(:dir => directory,
                               :default_slop => 2,
                               :handle_parse_errors => false)

You can also pass a block if you like. The index will be yielded and closed at the index of the box. For example;

      Ferret::I.new() do |index|
        # do stuff with index. Most of your actions will be cached.
      end

### Public Instance methods

<<(doc, analyzer = nil)

Alias for add_document

[](*arg)

Alias for doc

add_document(doc, analyzer = nil)

Adds a document to this index, using the provided analyzer instead of the local analyzer if provided. If the document contains more than IndexWriter::MAX_FIELD_LENGTH terms for a given field, the remainder are discarded.

There are three ways to add a document to the index. To add a document you can simply add a string or an array of strings. This will store all the strings in the "" (ie empty string) field (unless you specify the default_field when you create the index).

      index << "This is a new document to be indexed"
      index << ["And here", "is another", "new document", "to be indexed"]

But these are pretty simple documents. If this is all you want to index you could probably just use SimpleSearch. So let‘s give our documents some fields;

      index << {:title => "Programming Ruby", :content => "blah blah blah"}
      index << {:title => "Programming Ruby", :content => "yada yada yada"}

Or if you are indexing data stored in a database, you‘ll probably want to store the id;

      index << {:id => row.id, :title => row.title, :date => row.date}

See FieldInfos for more information on how to set field properties.

add_indexes(indexes)

Merges all segments from an index or an array of indexes into this index. You can pass a single Index::Index, Index::Reader, Store::Directory or an array of any single one of these.

This may be used to parallelize batch indexing. A large document collection can be broken into sub-collections. Each sub-collection can be indexed in parallel, on a different thread, process or machine and perhaps all in memory. The complete index can then be created by merging sub-collection indexes with this method.

After this completes, the index is optimized.

close()

Closes this index by closing its associated reader and writer objects.

commit()

Alias for flush

delete(arg)

Deletes a document/documents from the index. The method for determining the document to delete depends on the type of the argument passed.

If `arg` is an Integer then delete the document based on the internal document number. Will raise an error if the document does not exist.

If `arg` is a String then search for the documents with `arg` in the `id` field. The `id` field is either :id or whatever you set :id_field parameter to when you create the Index object. Will fail quietly if the no document exists.

deleted?(n)

Returns true if document `n` has been deleted

doc(*arg)

Retrieves a document/documents from the index. The method for retrieval depends on the type of the argument passed.

If `arg` is an Integer then return the document based on the internal document number.

If `arg` is a Range, then return the documents within the range based on internal document number.

If `arg` is a String then search for the first document with `arg` in the `id` field. The `id` field is either :id or whatever you set :id_field parameter to when you create the Index object.

explain(query, doc)

Returns an Explanation that describes how `doc` scored against `query`.

This is intended to be used in developing Similarity implementations, and, for good performance, should not be displayed with every hit. Computing an explanation is as expensive as executing the query over the entire index.

field_infos()

Returns the field_infos object so that you can add new fields to the index.

flush()

Flushes all writes to the index. This will not optimize the index but it will make sure that all writes are written to it.

NOTE: this is not necessary if you are only using this class. All writes will automatically flush when you perform an operation that reads the index.

has_deletions?()

Returns true if any documents have been deleted since the index was last flushed.

highlight(query, doc_id, options = {})

Returns an array of strings with the matches highlighted. The `query` can either a query String or a Ferret::Search::Query object. The doc_id is the id of the document you want to highlight (usually returned by the search methods). There are also a number of options you can pass;

### Options

field: | Default: @options[:default_field]. The default_field is the field that is usually highlighted but you can specify which field you want to highlight here. If you want to highlight multiple fields then you will need to call this method multiple times.
excerpt_length: | Default: 150. Length of excerpt to show. Highlighted terms will be in the centre of the excerpt. Set to :all to highlight the entire field.
num_excerpts: | Default: 2. Number of excerpts to return.
pre_tag: | Default: "<b>". Tag to place to the left of the match. You‘ll probably want to change this to a "<span>" tag with a class. Try "\033[36m" for use in a terminal.
post_tag: | Default: "</b>". This tag should close the +:pre_tag+. Try tag "\033[m" in the terminal.
ellipsis: | Default: "…". This is the string that is appended at the beginning and end of excerpts (unless the excerpt hits the start or end of the field. Alternatively you may want to use the HTML entity &8230; or the UTF-8 string "\342\200\246".

optimize()

optimizes the index. This should only be called when the index will no longer be updated very often, but will be read a lot.

persist(directory, create = true)

This is a simple utility method for saving an in memory or RAM index to the file system. The same thing can be achieved by using the Index::Index#add_indexes method and you will have more options when creating the new index, however this is a simple way to turn a RAM index into a file system index.

directory: | This can either be a Store::Directory object or a String representing the path to the directory where you would like to store the index.
create: | True if you‘d like to create the directory if it doesn‘t exist or copy over an existing directory. False if you‘d like to merge with the existing directory. This defaults to false.

process_query(query)

Turn a query string into a Query object with the Index‘s QueryParser

query_delete(query)

Delete all documents returned by the query.

query: | The query to find documents you wish to delete. Can either be a string (in which case it is parsed by the standard query parser) or an actual query object.

query_update(query, new_val)

Update all the documents returned by the query.

query: | The query to find documents you wish to update. Can either be a string (in which case it is parsed by the standard query parser) or an actual query object.
new_val: | The values we are updating. This can be a string in which case the default field is updated, or it can be a hash, in which case, all fields in the hash are merged into the old hash. That is, the old fields are replaced by values in the new hash if they exist.

### Example

      index << {:id => "26", :title => "Babylon", :artist => "David Grey"}
      index << {:id => "29", :title => "My Oh My", :artist => "David Grey"}

      # correct
      index.query_update('artist:"David Grey"', {:artist => "David Gray"})

      index["26"]
        #=> {:id => "26", :title => "Babylon", :artist => "David Gray"}
      index["28"]
        #=> {:id => "28", :title => "My Oh My", :artist => "David Gray"}

reader()

Get the reader for this index.

NOTE: | This will close the writer from this index.

search(query, options = {})

Run a query through the Searcher on the index. A TopDocs object is returned with the relevant results. The `query` is a built in Query object or a query string that can be parsed by the Ferret::QueryParser. Here are the options;

### Options

offset: | Default: 0. The offset of the start of the section of the result-set to return. This is used for paging through results. Let‘s say you have a page size of 10. If you don‘t find the result you want among the first 10 results then set +:offset+ to 10 and look at the next 10 results, then 20 and so on.
limit: | Default: 10. This is the number of results you want returned, also called the page size. Set +:limit+ to +:all+ to return all results

sort:

A Sort object or sort string describing how the field should be sorted. A sort string is made up of field names which cannot contain spaces and the word "DESC" if you want the field reversed, all separated by commas. For example; "rating DESC, author, title". Note that Ferret will try to determine a field‘s type by looking at the first term in the index and seeing if it can be parsed as an integer or a float. Keep this in mind as you may need to specify a fields type to sort it correctly. For more on this, see the documentation for SortField

filter: | a Filter object to filter the search results with
filter_proc: | a filter Proc is a Proc which takes the doc_id, the score and the Searcher object as its parameters and returns a Boolean value specifying whether the result should be included in the result set.

search_each(query, options = {}) {|doc, score| ...}

Run a query through the Searcher on the index. A TopDocs object is returned with the relevant results. The `query` is a Query object or a query string that can be validly parsed by the Ferret::QueryParser. The Searcher#search_each method yields the internal document id (used to reference documents in the Searcher object like this; +searcher[doc_id]+) and the search score for that document. It is possible for the score to be greater than 1.0 for some queries and taking boosts into account. This method will also normalize scores to the range 0.0..1.0 when the max-score is greater than 1.0. Here are the options;

### Options

offset: | Default: 0. The offset of the start of the section of the result-set to return. This is used for paging through results. Let‘s say you have a page size of 10. If you don‘t find the result you want among the first 10 results then set +:offset+ to 10 and look at the next 10 results, then 20 and so on.
limit: | Default: 10. This is the number of results you want returned, also called the page size. Set +:limit+ to +:all+ to return all results

sort:

A Sort object or sort string describing how the field should be sorted. A sort string is made up of field names which cannot contain spaces and the word "DESC" if you want the field reversed, all separated by commas. For example; "rating DESC, author, title". Note that Ferret will try to determine a field‘s type by looking at the first term in the index and seeing if it can be parsed as an integer or a float. Keep this in mind as you may need to specify a fields type to sort it correctly. For more on this, see the documentation for SortField

filter: | a Filter object to filter the search results with
filter_proc: | a filter Proc is a Proc which takes the doc_id, the score and the Searcher object as its parameters and returns a Boolean value specifying whether the result should be included in the result set.
returns: | The total number of hits.

### Example

eg.

      index.search_each(query, options = {}) do |doc, score|
        puts "hit document number #{doc} with a score of #{score}"
      end

searcher()

Get the searcher for this index.

NOTE: | This will close the writer from this index.

size()

returns the number of documents in the index

to_s()
update(id, new_doc)

Update the document referenced by the document number `id` if `id` is an integer or all of the documents which have the term `id` if `id` is a term..

id: | The number of the document to update. Can also be a string representing the value in the `id` field. Also consider using the :key attribute.
new_doc: | The document to replace the old document with

writer()

Get the writer for this index.

NOTE: | This will close the reader from this index.

### Protected Instance methods

ensure_reader_open(get_latest = true)

returns the new reader if one is opened

ensure_searcher_open()
ensure_writer_open()

[Validate]