Previous Next

Extensibility

Text Analysis

The Zend_Search_Lucene_Analysis_Analyzer class is used by the indexer to tokenize document text fields.

The Zend_Search_Lucene_Analysis_Analyzer::getDefault() and Zend_Search_Lucene_Analysis_Analyzer::setDefault() methods are used to get and set the default analyzer.

You can assign your own text analyzer or choose it from the set of predefined analyzers: Zend_Search_Lucene_Analysis_Analyzer_Common_Text and Zend_Search_Lucene_Analysis_Analyzer_Common_Text_CaseInsensitive (default). Both of them interpret tokens as sequences of letters. Zend_Search_Lucene_Analysis_Analyzer_Common_Text_CaseInsensitive converts all tokens to lower case.

To switch between analyzers:

Zend_Search_Lucene_Analysis_Analyzer::setDefault(
    new Zend_Search_Lucene_Analysis_Analyzer_Common_Text());
...
$index->addDocument($doc);

The Zend_Search_Lucene_Analysis_Analyzer_Common class is designed to be an ancestor of all user defined analyzers. User should only define the reset() and nextToken() methods, which takes its string from the $_input member and returns tokens one by one (a null value indicates the end of the stream).

The nextToken() method should call the normalize() method on each token. This will allow you to use token filters with your analyzer.

Here is an example of a custom analyzer, which accepts words with digits as terms:

Example #1 Custom text Analyzer.

/**
 * Here is a custom text analyser, which treats words with digits as
 * one term
 */

class My_Analyzer extends Zend_Search_Lucene_Analysis_Analyzer_Common
{
    private $_position;

    /**
     * Reset token stream
     */
    public function reset()
    {
        $this->_position = 0;
    }

    /**
     * Tokenization stream API
     * Get next token
     * Returns null at the end of stream
     *
     * @return Zend_Search_Lucene_Analysis_Token|null
     */
    public function nextToken()
    {
        if ($this->_input === null) {
            return null;
        }

        while ($this->_position < strlen($this->_input)) {
            // skip white space
            while ($this->_position < strlen($this->_input) &&
                   !ctype_alnum( $this->_input[$this->_position] )) {
                $this->_position++;
            }

            $termStartPosition = $this->_position;

            // read token
            while ($this->_position < strlen($this->_input) &&
                   ctype_alnum( $this->_input[$this->_position] )) {
                $this->_position++;
            }

            // Empty token, end of stream.
            if ($this->_position == $termStartPosition) {
                return null;
            }

            $token = new Zend_Search_Lucene_Analysis_Token(
                                      substr($this->_input,
                                             $termStartPosition,
                                             $this->_position -
                                             $termStartPosition),
                                      $termStartPosition,
                                      $this->_position);
            $token = $this->normalize($token);
            if ($token !== null) {
                return $token;
            }
            // Continue if token is skipped
        }

        return null;
    }
}

Zend_Search_Lucene_Analysis_Analyzer::setDefault(
    new My_Analyzer());

Tokens Filtering

The Zend_Search_Lucene_Analysis_Analyzer_Common analyzer also offers a token filtering mechanism.

The Zend_Search_Lucene_Analysis_TokenFilter class provides an abstract interface for such filters. Your own filters should extend this class either directly or indirectly.

Any custom filter must implement the normalize() method which may transform input token or signal that the current token should be skipped.

There are three filters already defined in the analysis subpackage:

  • Zend_Search_Lucene_Analysis_TokenFilter_LowerCase

  • Zend_Search_Lucene_Analysis_TokenFilter_ShortWords

  • Zend_Search_Lucene_Analysis_TokenFilter_StopWords

The LowerCase filter is already used for Zend_Search_Lucene_Analysis_Analyzer_Common_Text_CaseInsensitive analyzer by default.

The ShortWords and StopWords filters may be used with pre-defined or custom analyzers like this:

$stopWords = array('a', 'an', 'at', 'the', 'and', 'or', 'is', 'am');
$stopWordsFilter =
    new Zend_Search_Lucene_Analysis_TokenFilter_StopWords($stopWords);

$analyzer =
    new Zend_Search_Lucene_Analysis_Analyzer_Common_TextNum_CaseInsensitive();
$analyzer->addFilter($stopWordsFilter);

Zend_Search_Lucene_Analysis_Analyzer::setDefault($analyzer);
$shortWordsFilter = new Zend_Search_Lucene_Analysis_TokenFilter_ShortWords();

$analyzer =
    new Zend_Search_Lucene_Analysis_Analyzer_Common_TextNum_CaseInsensitive();
$analyzer->addFilter($shortWordsFilter);

Zend_Search_Lucene_Analysis_Analyzer::setDefault($analyzer);

The Zend_Search_Lucene_Analysis_TokenFilter_StopWords constructor takes an array of stop-words as an input. But stop-words may be also loaded from a file:

$stopWordsFilter = new Zend_Search_Lucene_Analysis_TokenFilter_StopWords();
$stopWordsFilter->loadFromFile($my_stopwords_file);

$analyzer =
   new Zend_Search_Lucene_Analysis_Analyzer_Common_TextNum_CaseInsensitive();
$analyzer->addFilter($stopWordsFilter);

Zend_Search_Lucene_Analysis_Analyzer::setDefault($analyzer);
This file should be a common text file with one word in each line. The '#' character marks a line as a comment.

The Zend_Search_Lucene_Analysis_TokenFilter_ShortWords constructor has one optional argument. This is the word length limit, set by default to 2.

Scoring Algorithms

The score of a document d for a query q is defined as follows:

score(q,d) = sum( tf(t in d) * idf(t) * getBoost(t.field in d) * lengthNorm(t.field in d) ) * coord(q,d) * queryNorm(q)

tf(t in d) - Zend_Search_Lucene_Search_Similarity::tf($freq) - a score factor based on the frequency of a term or phrase in a document.

idf(t) - Zend_Search_Lucene_Search_Similarity::tf($term, $reader) - a score factor for a simple term with the specified index.

getBoost(t.field in d) - the boost factor for the term field.

lengthNorm($term) - the normalization value for a field given the total number of terms contained in a field. This value is stored within the index. These values, together with field boosts, are stored in an index and multiplied into scores for hits on each field by the search code.

Matches in longer fields are less precise, so implementations of this method usually return smaller values when numTokens is large, and larger values when numTokens is small.

coord(q,d) - Zend_Search_Lucene_Search_Similarity::coord($overlap, $maxOverlap) - a score factor based on the fraction of all query terms that a document contains.

The presence of a large portion of the query terms indicates a better match with the query, so implementations of this method usually return larger values when the ratio between these parameters is large and smaller values when the ratio between them is small.

queryNorm(q) - the normalization value for a query given the sum of the squared weights of each of the query terms. This value is then multiplied into the weight of each query term.

This does not affect ranking, but rather just attempts to make scores from different queries comparable.

The scoring algorithm can be customized by defining your own Similarity class. To do this extend the Zend_Search_Lucene_Search_Similarity class as defined below, then use the Zend_Search_Lucene_Search_Similarity::setDefault($similarity); method to set it as default.

class MySimilarity extends Zend_Search_Lucene_Search_Similarity {
    public function lengthNorm($fieldName, $numTerms) {
        return 1.0/sqrt($numTerms);
    }

    public function queryNorm($sumOfSquaredWeights) {
        return 1.0/sqrt($sumOfSquaredWeights);
    }

    public function tf($freq) {
        return sqrt($freq);
    }

    /**
     * It's not used now. Computes the amount of a sloppy phrase match,
     * based on an edit distance.
     */
    public function sloppyFreq($distance) {
        return 1.0;
    }

    public function idfFreq($docFreq, $numDocs) {
        return log($numDocs/(float)($docFreq+1)) + 1.0;
    }

    public function coord($overlap, $maxOverlap) {
        return $overlap/(float)$maxOverlap;
    }
}

$mySimilarity = new MySimilarity();
Zend_Search_Lucene_Search_Similarity::setDefault($mySimilarity);

Storage Containers

The abstract class Zend_Search_Lucene_Storage_Directory defines directory functionality.

The Zend_Search_Lucene constructor uses either a string or a Zend_Search_Lucene_Storage_Directory object as an input.

The Zend_Search_Lucene_Storage_Directory_Filesystem class implements directory functionality for a file system.

If a string is used as an input for the Zend_Search_Lucene constructor, then the index reader (Zend_Search_Lucene object) treats it as a file system path and instantiates the Zend_Search_Lucene_Storage_Directory_Filesystem object.

You can define your own directory implementation by extending the Zend_Search_Lucene_Storage_Directory class.

Zend_Search_Lucene_Storage_Directory methods:

abstract class Zend_Search_Lucene_Storage_Directory {
/**
 * Closes the store.
 *
 * @return void
 */
abstract function close();


/**
 * Creates a new, empty file in the directory with the given $filename.
 *
 * @param string $name
 * @return void
 */
abstract function createFile($filename);


/**
 * Removes an existing $filename in the directory.
 *
 * @param string $filename
 * @return void
 */
abstract function deleteFile($filename);


/**
 * Returns true if a file with the given $filename exists.
 *
 * @param string $filename
 * @return boolean
 */
abstract function fileExists($filename);


/**
 * Returns the length of a $filename in the directory.
 *
 * @param string $filename
 * @return integer
 */
abstract function fileLength($filename);


/**
 * Returns the UNIX timestamp $filename was last modified.
 *
 * @param string $filename
 * @return integer
 */
abstract function fileModified($filename);


/**
 * Renames an existing file in the directory.
 *
 * @param string $from
 * @param string $to
 * @return void
 */
abstract function renameFile($from, $to);


/**
 * Sets the modified time of $filename to now.
 *
 * @param string $filename
 * @return void
 */
abstract function touchFile($filename);


/**
 * Returns a Zend_Search_Lucene_Storage_File object for a given
 * $filename in the directory.
 *
 * @param string $filename
 * @return Zend_Search_Lucene_Storage_File
 */
abstract function getFileObject($filename);

}

The getFileObject($filename) method of a Zend_Search_Lucene_Storage_Directory instance returns a Zend_Search_Lucene_Storage_File object.

The Zend_Search_Lucene_Storage_File abstract class implements file abstraction and index file reading primitives.

You must also extend Zend_Search_Lucene_Storage_File for your directory implementation.

Only two methods of Zend_Search_Lucene_Storage_File must be overridden in your implementation:

class MyFile extends Zend_Search_Lucene_Storage_File {
    /**
     * Sets the file position indicator and advances the file pointer.
     * The new position, measured in bytes from the beginning of the file,
     * is obtained by adding offset to the position specified by whence,
     * whose values are defined as follows:
     * SEEK_SET - Set position equal to offset bytes.
     * SEEK_CUR - Set position to current location plus offset.
     * SEEK_END - Set position to end-of-file plus offset. (To move to
     * a position before the end-of-file, you need to pass a negative value
     * in offset.)
     * Upon success, returns 0; otherwise, returns -1
     *
     * @param integer $offset
     * @param integer $whence
     * @return integer
     */
    public function seek($offset, $whence=SEEK_SET) {
        ...
    }

    /**
     * Read a $length bytes from the file and advance the file pointer.
     *
     * @param integer $length
     * @return string
     */
    protected function _fread($length=1) {
        ...
    }
}
Previous Next
Introduction to Zend Framework
Overview
Installation
Zend_Acl
Introduction
Refining Access Controls
Advanced Usage
Zend_Amf
Introduction
Zend_Amf_Server
Zend_Auth
Introduction
Database Table Authentication
Digest Authentication
HTTP Authentication Adapter
LDAP Authentication
Open ID Authentication
Zend_Cache
Introduction
The theory of caching
Zend_Cache frontends
Zend_Cache backends
Zend_Captcha
Introduction
Captcha Operation
Captcha Adapters
Zend_Config
Introduction
Theory of Operation
Zend_Config_Ini
Zend_Config_Xml
Zend_Config_Writer
Zend_Config_Writer
Zend_Console_Getopt
Introduction to Getopt
Declaring Getopt Rules
Fetching Options and Arguments
Configuring Zend_Console_Getopt
Zend_Controller
Zend_Controller Quick Start
Zend_Controller Basics
The Front Controller
The Request Object
The Standard Router
The Dispatcher
Action Controllers
Action Helpers
The Response Object
Plugins
Using a Conventional Modular Directory Structure
MVC Exceptions
Migrating from Previous Versions
Zend_Currency
Introduction to Zend_Currency
How to work with currencies
Migrating from Previous Versions
Zend_Date
Introduction
Theory of Operation
Basic Methods
Zend_Date API Overview
Creation of dates
Constants for General Date Functions
Working examples
Zend_Db
Zend_Db_Adapter
Zend_Db_Statement
Zend_Db_Profiler
Zend_Db_Select
Zend_Db_Table
Zend_Db_Table_Row
Zend_Db_Table_Rowset
Zend_Db_Table Relationships
Zend_Debug
Dumping Variables
Zend_Dojo
Introduction
Zend_Dojo_Data: dojo.data Envelopes
Dojo View Helpers
Dojo Form Elements and Decorators
Zend_Dom
Introduction
Zend_Dom_Query
Zend_Exception
Using Exceptions
Zend_Feed
Introduction
Importing Feeds
Retrieving Feeds from Web Pages
Consuming an RSS Feed
Consuming an Atom Feed
Consuming a Single Atom Entry
Modifying Feed and Entry structures
Custom Feed and Entry Classes
Zend_File
Zend_File_Transfer
Validators for Zend_File_Transfer
Filters for Zend_File_Transfer
Migrating from previous versions
Zend_Filter
Introduction
Standard Filter Classes
Filter Chains
Writing Filters
Zend_Filter_Input
Zend_Filter_Inflector
Zend_Form
Zend_Form
Zend_Form Quick Start
Creating Form Elements Using Zend_Form_Element
Creating Forms Using Zend_Form
Creating Custom Form Markup Using Zend_Form_Decorator
Standard Form Elements Shipped With Zend Framework
Standard Form Decorators Shipped With Zend Framework
Internationalization of Zend_Form
Advanced Zend_Form Usage
Zend_Gdata
Introduction to Gdata
Authenticating with AuthSub
Using the Book Search Data API
Authenticating with ClientLogin
Using Google Calendar
Using Google Documents List Data API
Using Google Health
Using Google Spreadsheets
Using Google Apps Provisioning
Using Google Base
Using Picasa Web Albums
Using the YouTube Data API
Catching Gdata Exceptions
Zend_Http
Zend_Http_Client - Introduction
Zend_Http_Client - Advanced Usage
Zend_Http_Client - Connection Adapters
Zend_Http_Cookie and Zend_Http_CookieJar
Zend_Http_Response
Zend_InfoCard
Introduction
Zend_Json
Introduction
Basic Usage
JSON Objects
XML to JSON conversion
Zend_Json_Server - JSON-RPC server
Zend_Layout
Introduction
Zend_Layout Quick Start
Zend_Layout Configuration Options
Zend_Layout Advanced Usage
Zend_Ldap
Introduction
Zend_Loader
Loading Files and Classes Dynamically
Loading Plugins
Zend_Locale
Introduction
Using Zend_Locale
Normalization and Localization
Working with Dates and Times
Supported locales
Migrating from previous versions
Zend_Log
Overview
Writers
Formatters
Filters
Zend_Mail
Introduction
Sending via SMTP
Sending Multiple Mails per SMTP Connection
Using Different Transports
HTML E-Mail
Attachments
Adding Recipients
Controlling the MIME Boundary
Additional Headers
Character Sets
Encoding
SMTP Authentication
Securing SMTP Transport
Reading Mail Messages
Zend_Measure
Introduction
Creation of Measurements
Outputting measurements
Manipulating Measurements
Types of measurements
Zend_Memory
Overview
Memory Manager
Memory Objects
Zend_Mime
Zend_Mime
Zend_Mime_Message
Zend_Mime_Part
Zend_OpenId
Introduction
Zend_OpenId_Consumer Basics
Zend_OpenId_Provider
Zend_Paginator
Introduction
Usage
Configuration
Advanced usage
Zend_Pdf
Introduction.
Creating and loading PDF documents.
Save changes to the PDF document.
Document pages.
Drawing
Document Info and Metadata.
Zend_Pdf module usage example
Zend_ProgressBar
Zend_ProgressBar
Zend_Registry
Using the Registry
Zend_Rest
Introduction
Zend_Rest_Client
Zend_Rest_Server
Zend_Search_Lucene
Overview
Building Indexes
Searching an Index
Query Language
Query Construction API
Character Set
Extensibility
Interoperating with Java Lucene
Advanced
Best Practices
Zend_Server
Introduction
Zend_Server_Reflection
Zend_Service
Introduction
Zend_Service_Akismet
Zend_Service_Amazon
Zend_Service_Audioscrobbler
Zend_Service_Delicious
Zend_Service_Flickr
Zend_Service_Nirvanix
Zend_Service_ReCaptcha
Zend_Service_Simpy
Introduction
Zend_Service_StrikeIron
Zend_Service_StrikeIron: Bundled Services
Zend_Service_StrikeIron: Advanced Uses
Zend_Service_Technorati
Zend_Service_Twitter
Zend_Service_Yahoo
Zend_Session
Introduction
Basic Usage
Advanced Usage
Global Session Management
Zend_Session_SaveHandler_DbTable
Zend_Soap
Zend_Soap_Server
Zend_Soap_Client
WSDL Accessor
AutoDiscovery
Zend_Test
Introduction
Zend_Test_PHPUnit
Zend_Text
Zend_Text_Figlet
Zend_Text_Table
Zend_TimeSync
Introduction
Working with Zend_TimeSync
Zend_Translate
Introduction
Adapters for Zend_Translate
Using Translation Adapters
Migrating from previous versions
Zend_Uri
Zend_Uri
Zend_Validate
Introduction
Standard Validation Classes
Validator Chains
Writing Validators
Zend_Version
Reading the Zend Framework Version
Zend_View
Introduction
Controller Scripts
View Scripts
View Helpers
Zend_View_Abstract
Zend_Wildfire
Zend_Wildfire
Zend_XmlRpc
Introduction
Zend_XmlRpc_Client
Zend_XmlRpc_Server
Zend Framework Requirements
PHP Version
PHP Extensions
Zend Framework Components
Zend Framework Dependencies
Zend Framework Coding Standard for PHP
Overview
PHP File Formatting
Naming Conventions
Coding Style
Zend Framework Performance Guide
Introduction
Class Loading
Internationalization (i18n) and Localization (l10n)
View Rendering
Copyright Information