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NAME
mifluz - C++ library to use and manage inverted indexes
SYNOPSIS
#include <mifluz.h>
main()
{
Configuration* config = WordContext::Initialize();
WordList* words = new WordList(*config);
...
delete words;
WordContext::Finish();
}
DESCRIPTION
The purpose of mifluz is to provide a C++ library to build and query a
full text inverted index. It is dynamically updatable, scalable (up to
1Tb indexes), uses a controlled amount of memory, shares index files
and memory cache among processes or threads and compresses index files
to 50% of the raw data. The structure of the index is configurable at
runtime and allows inclusion of relevance ranking information. The
query functions do not require loading all the occurrences of a
searched term. They consume very few resources and many searches can
be run in parallel.
The file management library used in mifluz is a modified Berkeley DB
(www.sleepycat.com) version 3.1.14.
CLASSES AND COMMANDS
Configuration
reads the configuration file and manages it in memory.
WordContext
read configuration and setup mifluz context.
WordCursor
abstract class to search and retrieve entries in a WordList
object.
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WordCursorOne
search and retrieve entries in a WordListOne object.
WordDBInfo
inverted index usage environment.
WordDict
manage and use an inverted index dictionary.
WordKey
inverted index key.
WordKeyInfo
information on the key structure of the inverted index.
WordList
abstract class to manage and use an inverted index file.
WordListOne
manage and use an inverted index file.
WordMonitor
monitoring classes activity.
WordRecord
inverted index record.
WordRecordInfo
information on the record structure of the inverted index.
WordReference
inverted index occurrence.
WordType
defines a word in term of allowed characters, length etc.
htdb_dump
dump the content of an inverted index in Berkeley DB fashion
htdb_load
displays statistics for Berkeley DB environments.
htdb_stat
displays statistics for Berkeley DB environments.
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mifluzdict
dump the dictionnary of an inverted index.
mifluzdump
dump the content of an inverted index.
mifluzload
load the content of an inverted index.
mifluzsearch
search the content of an inverted index.
CONFIGURATION
The format of the configuration file read by WordContext::Initialize
is:
keyword: value
Comments may be added on lines starting with a #. The default
configuration file is read from from the file pointed by the
MIFLUZ_CONFIG environment variable or ~/.mifluz or /etc/mifluz.conf in
this order. If no configuration file is available, builtin defaults
are used. Here is an example configuration file:
wordlist_extend: true
wordlist_cache_size: 10485760
wordlist_page_size: 32768
wordlist_compress: 1
wordlist_wordrecord_description: NONE
wordlist_wordkey_description: Word/DocID 32/Flags 8/Location 16
wordlist_monitor: true
wordlist_monitor_period: 30
wordlist_monitor_output: monitor.out,rrd
wordlist_allow_numbers {true|false} <number> (default false)
A digit is considered a valid character within a word if this
configuration parameter is set to true otherwise it is an error
to insert a word containing digits. See the Normalize method for
more information.
wordlist_cache_inserts {true|false} (default false)
If true all Insert calls are cached in memory. When the WordList
object is closed or a different access method is called the
cached entries are flushed in the inverted index.
wordlist_cache_max <bytes> (default 0)
Maximum size of the cumulated cache files generated when doing
bulk insertion with the BatchStart() function. When this limit is
reached, the cache files are all merged into the inverted index.
The value 0 means infinite size allowed. See WordList(3) for the
rationale behind cache file handling.
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wordlist_cache_size <bytes> (default 500K)
Berkeley DB cache size (see Berkeley DB documentation) Cache
makes a huge difference in performance. It must be at least 2% of
the expected total data size. Note that if compression is
activated the data size is eight times larger than the actual
file size. In this case the cache must be scaled to 2% of the
data size, not 2% of the file size. See Cache tuning in the
mifluz guide for more hints. See WordList(3) for the rationale
behind cache file handling.
wordlist_compress {true|false} (default false)
Activate compression of the index. The resulting index is eight
times smaller than the uncompressed index.
wordlist_env_dir <directory> (default .)
Only valid if wordlist_env_share set to true. Specify the
directory in which the sharable environment will be created. All
inverted indexes specified with a non-absolute pathname will be
created relative to this directory.
wordlist_env_share {true,false} (default false)
If true a sharable environment is open or created if none exist.
wordlist_env_skip {true,false} (default false)
If true no environment is created at all. This must never be used
if a WordList object is created. It may be useful if only WordKey
objects are used, for instance.
wordlist_extend {true|false} (default false)
If true maintain reference count of unique words. The Noccurrence
method gives access to this count.
wordlist_locale <locale> (default C)
Set the locale of the program to locale for more information.
wordlist_lowercase {true|false} <number> (default true)
If a word contains upper case letters it is converted to
lowercase if this configuration parameter is true, otherwise it
is left untouched.
wordlist_maximum_word_length <number> (default 25)
The maximum length of a word. See the Normalize method for more
information.
wordlist_mimimun_word_length <number> (default 3)
The minimum length of a word. See the Normalize method for more
information.
wordlist_monitor {true|false} (default false)
If true create a WordMonitor instance to gather statistics and
build reports.
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wordlist_monitor_output <file>[,{rrd,readable] (default stderr)
Print reports on file instead of the default stderr If type is
set to rrd the output is fit for the benchmark-report script.
Otherwise it a (hardly :-) readable string.
wordlist_monitor_period <sec> (default 0)
If the value sec is a positive integer, set a timer to print
reports every sec seconds. The timer is set using the ALRM signal
and will fail if the calling application already has a handler on
that signal.
wordlist_page_size <bytes> (default 8192)
Berkeley DB page size (see Berkeley DB documentation)
wordlist_truncate {true|false} <number> (default true)
If a word is too long according to the
wordlist_maximum_word_length it is truncated if this
configuration parameter is true otherwise it is considered an
invalid word.
wordlist_valid_punctuation [characters] (default none)
A list of punctuation characters that may appear in a word. These
characters will be removed from the word before insertion in the
index.
wordlist_verbose <number> (default 0)
Set the verbosity level of the WordList class.
1 walk logic
2 walk logic details
3 walk logic lots of details
wordlist_wordkey_description <desc> (no default)
Describe the structure of the inverted index key. In the
following explanation of the <desc> format, mandatory words are
in bold and values that must be replaced in italic.
Word bits/name bits [/...]
The name is an alphanumerical symbolic name for the key field.
The bits is the number of bits required to store this field.
Note that all values are stored in unsigned integers (unsigned
int). Example:
Word 8/Document 16/Location 8
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wordlist_wordkey_document [field ...] (default none)
A white space separated list of field numbers that define a
document. The field number list must not contain gaps. For
instance 1 2 3 is valid but 1 3 4 is not valid. This
configuration parameter is not used by the mifluz library but may
be used by a query application to define the semantic of a
document. In response to a query, the application will return a
list of results in which only distinct documents will be shown.
wordlist_wordkey_location field (default none)
A single field number that contains the position of a word in a
given document. This configuration parameter is not used by the
mifluz library but may be used by a query application.
wordlist_wordrecord_description {NONE|DATA|STR} (no default)
NONE: the record is empty
DATA: the record contains an integer (unsigned int)
STR: the record contains a string (String)
ENVIRONMENT
MIFLUZ_CONFIG file name of configuration file read by WordContext(3).
Defaults to ~/.mifluz. or /usr/etc/mifluz.conf
AUTHORS
Loic Dachary loic@gnu.org
The Ht://Dig group http://dev.htdig.org/
SEE ALSO
htdb_dump(1), htdb_stat(1), htdb_load(1), mifluzdump(1),
mifluzload(1), mifluzsearch(1), mifluzdict(1), WordContext(3),
WordList(3), WordDict(3), WordListOne(3), WordKey(3), WordKeyInfo(3),
WordType(3), WordDBInfo(3), WordRecordInfo(3), WordRecord(3),
WordReference(3), WordCursor(3), WordCursorOne(3), WordMonitor(3),
Configuration(3)
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