Provided by: swish-e_2.4.7-5ubuntu1_amd64 
NAME
SWISH::API - Perl interface to the Swish-e C Library
SYNOPSIS
use SWISH::API;
my $swish = SWISH::API->new( 'index.swish-e' );
$swish->abort_last_error
if $swish->Error;
# A short-cut way to search
my $results = $swish->query( "foo OR bar" );
# Or more typically
my $search = $swish->new_search_object;
# then in a loop
my $results = $search->execute( $query );
# always check for errors (but aborting is not always necessary)
$swish->abort_last_error
if $swish->Error;
# Display a list of results
my $hits = $results->hits;
if ( !$hits ) {
print "No Results\n";
return; /* for example *.
}
print "Found ", $results->hits, " hits\n";
# Seek to a given page - should check for errors
$results->seek_result( ($page-1) * $page_size );
while ( my $result = $results->next_result ) {
printf("Path: %s\n Rank: %lu\n Size: %lu\n Title: %s\n Index: %s\n Modified: %s\n Record #: %lu\n File #: %lu\n\n",
$result->property( "swishdocpath" ),
$result->property( "swishrank" ),
$result->property( "swishdocsize" ),
$result->property( "swishtitle" ),
$result->property( "swishdbfile" ),
$result->result_property_str( "swishlastmodified" ),
$result->property( "swishreccount" ),
$result->property( "swishfilenum" )
);
}
# display properties and metanames
for my $index_name ( $swish->index_names ) {
my @metas = $swish->meta_list( $index_name );
my @props = $swish->property_list( $index_name );
for my $m ( @metas ) {
my $name = $m->name;
my $id = $m->id;
my $type = $m->type;
}
# (repeat above for @props)
}
DESCRIPTION
This module provides a Perl interface to the Swish-e search engine. This module allows
embedding the swish-e search code into your application avoiding the need to fork to run
the swish-e binary and to keep an index file open when running multiple queries. This
results in increased search performance.
DEPENDENCIES
You must have installed Swish-e version 2.4 before building this module. Download from:
http://swish-e.org
OVERVIEW
This module includes a number of classes.
Searching consists of connecting to a swish-e index (or indexes), and then running queries
against the open index. Connecting to the index creates a swish object blessed into the
SWISH::API class.
A SWISH::API::Search object is created from the SWISH::API object. The SWISH::API::Search
object can have associated parameters (e.g. result sort order).
The SWISH::API::Search object is used to query the associated index file or files. A
query on a search object returns a results object of the class SWISH::API::Results. Then
individual results of the SWISH::API::Result class can be fetched by calling a method of
the results object.
Finally, a result's properties can be accessed by calling methods on the result object.
METHODS
SWISH::API - Swish Handle Object
To begin using Swish you must first create a Swish Handle object. This object makes the
connection to one or more index files and is used to create objects used for searching the
associated index files.
$swish = SWISH::API->new( $index_files );
This method returns a swish handle object blessed into the SWISH::API class.
$index_files is a space separated list of index files to open. This always returns an
object, even on errors. Caller must check for errors (see below).
@indexes = $swish->index_names;
Returns a list of index names associated with the swish handle. These were the
indexes specified as a parameter on the SWISH::API->new call. This can be used in
calls below that require specifying the index file name.
@header_names = $swish->header_names;
Returns a list of possible header names. These can be used to lookup header values.
See "Swishheader_value" method below.
@values = $swish->header_value( $index_file, $header_name );
A swish-e index has data associated with it stored in the index header. This method
provides access to that data.
Returns the header value for the header and index file specified. Most headers are a
single item, but some headers (e.g. "Stopwords") return a list.
The list of possible header names can be obtained from the Swishheader_names method.
$swish->rank_scheme( 0|1 );
Like the -R option with the swish-e command line tool. The default ranking scheme is
0. Set it to 1 to experiment with other ranking features. See the SWISH-CONFIG
documentation for more on ranking schemes.
$swish->return_raw_rank( 0|1 );
Like the -a option with the swish-e command line tool. The default, 0, return ranks
normalized to the range 0-1000. When enabled by setting to 1, ranks are returned 'raw'
(as computed by Swish-e internally during the search) and are only guaranteed to be
non-negative.
Error Handling
All errors are stored in and accessed via the SWISH::API object (the Swish Handle). That
is, even an error that occurs when calling a method on a result (SWISH::API::Result)
object will store the error in the parent SWISH:API object.
Check for errors after every method call. Some errors are critical errors and will
require destruction of the SWISH::API object. Critical errors will typically only happen
when attaching to the database and are errors such as an invalid index file name,
permissions errors, or passing invalid objects to calls.
Typically, if you receive an error when attaching to an index file or files you should
assume that the error is critical and let the swish object fall out of scope (and
destroyed). Otherwise, if an error is detected you should check if it is a critical
error. If the error is not critical you may continue using the objects that have been
created (for example, an invalid meta name will generate a non-critical error, so you may
continue searching using the same search object).
Error state is cleared upon a new query.
Again, all error methods need to be called on the parent swish object
$swish->error
Returns true if an error occurred on the last operation. On errors the value returned
is the internal Swish-e error number (which is less than zero).
$swish->critical_error
Returns true if the last error was a critical error
$swish->abort_last_error
Aborts the running program and prints an error message to STDERR.
$str = $swish->error_string
Returns the string description of the current error (based on the value returned by
$swish->error). This is a generic error string.
$msg = $swish->last_error_msg
Returns a string with specific information about the last error, if any. For example,
if a query of:
badmeta=foo
and "badmeta" is an invalid metaname $swish->error_string might return "Unknown
metaname", but $swish->last_error_msg might return "badmeta".
Generating Search and Result Objects
$search = $swish->new_search_object( $query );
This creates a new search object blessed into the SWISH::API::Search class. The
optional $query parameter is a query string to store in the search object.
See the section on "SWISH::API::Search" for methods available on the returned object.
The advantage of this method is that a search object can be used for multiple queries:
$search = $swish->New_Search_Objet;
while ( $query = next_query() ) {
$results = $search->execute( $query );
...
}
$results = $swish->query( $query );
This is a short-cut which avoids the step of creating a separate search object. It
returns a results object blessed into the SWISH::API::Results class described below.
This method basically is the equivalent of
$results = $swish->new_search_object->execute( $query );
SWISH::API::Search - Search Objects
A search object holds the parameters used to generate a list of results. These methods
are used to adjust these parameters and to create the list of results for the current set
of search parameters.
$search->set_query( $query );
This will set (or replace) the query string associated with a search object. This
method is typically not used as the query can be set when executing the actual query
or when creating a search object.
$search->set_structure( $structure_bits );
This method may change in the future.
A "structure" is a bit-mapped flag used to limit search results to specific parts of
an HTML document, such as the title or in H tags. The possible bits are:
IN_FILE = 1 This is the default
IN_TITLE = 2 In <title> tag
IN_HEAD = 4 In <head> tag
IN_BODY = 8 In <body>
IN_COMMENTS = 16 In html comments
IN_HEADER = 32 In <h*>
IN_EMPHASIZED = 64 In <em>, <b>, <strong>, <i>
IN_META = 128 In a meta tag (e.g. not swishdefault)
So if you wish to limit your searches to words in heading tags (e.g. <H1>) or in the
<title> tag use:
$search->set_structure( IN_HEAD | IN_TITLE );
$search->phrase_delimiter( $char );
Sets the character used as the phrase delimiter in searches. The default is double-
quotes (").
$search->set_search_limit( $property, $low, $high );
Sets a range from $low to $high inclusive that the given $property must be in to be
selected as a result. Call multiple times to set more than one limit on different
properties. Limits are ANDed, that is, a result must be within the range of all
limits specified to be included in a list of results.
For example to limit searches to documents modified in the last 48 hours:
my $start = time - 48 * 60 * 60;
$search->set_search_limit( 'swishlastmodified', $start, time() );
An error will be set if the property has already been specified or if $high < $low.
Other errors may not be reported until running the query, such as the property name is
invalid or if $low or $high are not numeric and the property specified is a numeric
property.
Once a query is run you cannot change the limit settings for the search object without
calling the reset_search_limit method first.
$search->reset_search_limit;
Clears the limit parameters for the given object. This must be called if the limit
parameters need to be changed.
$search->set_sort( $sort_string );
Sets the sort order of search results. The string is a space separated list of valid
document properties. Each property may contain a qualifier that sets the direction of
the sort.
For example, to sort the results by path name in ascending order and by rank in
descending order:
$search->set_sort( 'swishdocpath asc swishrank desc' );
The "asc" and "desc" qualifiers are optional, and if omitted ascending is assumed.
Currently, errors (e.g invalid property name) are not detected on this call, but
rather when executing a query. This may change in the future.
SWISH::API::Results - Generating and accessing results
Searching generates a results object blessed into the SWISH::API::Results class.
$results = $search->execute( $query );
Executes a query based on the parameters in the search object. $query is an optional
query string to use for the search ($query replaces the set query string in the search
object).
A typical use would be to create a search object once and then call this method for
each query using the same search object changing only the passed in $query.
The caller should check for errors after making this all.
Results Methods
A query creates a results object that contains information about the query (e.g. number of
hits) and access to the individual results.
$hits = $results->hits;
Returns the number of results for the query. If zero and no errors were reported
after calling $search->execute then the query returned zero results.
@parsed_words = $results->parsed_words( $index_name );
Returns an array of tokenized words and operators with stopwords removed. This is the
array of tokens used by swish for the query.
$index_name must match one of the index files specified on the creation of the swish
object (via the SWISH::API->new call).
The parsed words are useful for highlighting search terms in associated documents.
@removed_stopwords = $results->removed_stopwords( $index_name) ;
Returns an array of stopwords removed from a query, if any, for the index specified.
$index_name must match one of the index files specified on the creation of the swish
object (via the SWISH::API->new call).
$results->seek_result( $position );
Seeks to the position specified in the result list. Zero is the first position and
$results->hits-1 is the last position. Seeking past the end of results sets a non-
critical error condition.
Useful for seeking to a specific "page" of results.
$result = $results->next_result;
Fetches the next result from the list of results. Returns undef if no more results
are available. $result is an object blessed into the SWISH::API::Result class.
SWISH::API::Result - Result Methods
The follow methods provide access to data related to an individual result.
$prop = $result->property( $prop_name );
Fetches the property specified for the current result. An invalid property name will
cause an exception (which can be caught by wrapping the call in an eval block).
Can return undefined.
Date properties are returned as a timestamp. Use something like Date::Format to
format the strings (or just call scalar localtime( $prop ) ).
$prop = $result->result_property_str( $prop_name );
Fetches and formats the property. Unlike above, invalid property names return the
string "(null)" -- this will likely change to match the above (i.e. throw an
exception).
Undefined values are returned at the null string ("").
$value = $result->result_index_value( $header_name );
Returns the header value specified. This is similar to $swish->header_value(), but
the index file is not specified (it is determined by the result).
Utility Methods
@metas = $swish->meta_list( $index_name );
Swish-e has "MetaNames" which allow searching by fields in the index. This method
returns information about the Metanames.
Pass in the name of an open index file name and returns a list of SWISH::API::MetaName
objects. Three methods are currently defined on these objects:
$meta->name;
$meta->id;
$meta->type;
Name returns the name of the meta as defined in the MetaNames config option when the
index was created.
The id is the internal ID number used to represent the meta name.
type is the type of metaname. Currently only one type exists and its value is zero.
@props = $swish->property_list( $index_name );
Swish-e can store content or "properties" in the index and return this data when
running a query. A document's path, URL, title, size, date or summary are examples of
properites. Each property is accessed via its PropertyName. This method returns
information about the PropertNames stored in the index.
Pass in the name of an open index file name and returns a list of SWISH::API::MetaName
objects. Three methods are currently defined on these objects:
$prop->name;
$prop->id;
$prop->type;
name returns the name of the meta as defined in the MetaNames config option when the
index was created.
The id is the internal ID number used to represent the meta name.
type is the type of metaname. Currently only one type exists and its value is zero.
@propes = $result->property_list;
@meta = $result->meta_list;
These also return a list of Property or Metaname description objects, but are accessed
via a result record. Since the result comes from a specific index file there's no
need to specify the index file name.
$stemmed_word = $swish->stem_word( $word );
*Deprecated*
Returns the stemmed version of the passed in word.
Deprecated because only stems using the original Porter Stemmer and uses a shared
memory location in the SW_HANDLE object to store the stemmed word. See below for
other stemming options.
$fuzzy_word = $swish->Fuzzify( $indexname, $word );
Like stem_word() used to work, only it uses whatever stemmer is named in $indexname.
Returns the same kind of fuzzy_word object as the fuzzy_word() method.
$mode_string = $result->fuzzy_mode;
Returns the string (e.g. "Stemming_en", "Soundex", "None" ) indicating the stemming
method used while indexing the given document.
$fuzzy_word = $result->fuzzy_word( $word );
Converts $word using the same fuzzy mode used to index the $result. Returns a
SWISH::API::fuzzy_word object. Methods on the object are used to access the converted
words and other data as shown below.
$count = $fuzzy_word->word_count;
Returns the number of output words. Normally this is the value one, but may be more
depending on the stemmer used. DoubleMetaphone can return two strings for a single
input string.
$status = $fuzzy_word->word_error;
Returns any error code that the stemmer might set. Normally, this return value is
zero, indicating that the stemming/fuzzy operation succedded. The values returned are
defined in the swish-e source file /src/stemmer.h.
@words = $fuzzy_word->word_list;
Returns the converted words from the stemming/fuzzy operation. Normally, the array
will contain a single element, although may contain more (i.e. if DoubleMetaphone is
used and the input word returns two strings).
In the event that a word does not stem (e.g. trying to stem a number), this method
will return the original input word specified when $result->fuzzy_word( $word ) was
called.
@parsed_words = $swish->swish_words( $string, $index_file );
* Not implemented *
Splits up the input string into tokens of swish words and operators.
NOTES
Perl's garbage collection makes it easy to write code for searching with Swish-e, but care
must be taken not to keep objects around too long which can use up memory.
Here's an example of a potential problem. Say you have a very large number of documents
indexed and you want to find the first hit for a number of popular keywords (error
checking omitted in this bad example):
sub first_hit {
my $query = shift;
my $handle = SWISH::API->new( 'index.swish-e');
my $results = $handle->query( $query );
my $first_hit = $results->next_result;
return $first_hit;
}
my @first_hit_list;
for ( @keywords )
push @first_hit_list, $first_hit($_);
}
The first_hit() subroutine is returning a SWISH::Result object. That makes it easy to
access properties:
# print file names
for my $result ( @first_hit_list ) {
print $result->property('swishdocpath'),"\n";
}
But as long as a SWISH::API::Result object is around, so is the entire list of results
generated by the $handle->query() call, and the index file is still open (because a
SWISH::API::Result depends on a SWISH::API::Results object, which depends on a SWISH::API
object).
In this case it would be better to return from first_hit() just the properties you need:
...
my $first_hit = $results->next_result;
return $first_hit->property('swishdocpath');
}
Then when first_hit() sub ends the result list will be freed, and the index file closed,
thanks to Perl's reference count tracking.
Note: the other problem with the above code is that the same index file is opened for each
call to the function. Don't do that, instead open the index file once.
COPYRIGHT
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
AUTHOR
Bill Moseley moseley@hank.org. 2002/2003/2004
SUPPORT
Please contact the Swish-e discussion email list for support with this module or with
Swish-e. Please do not contact the developers directly.