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Manual Reference Pages  -  MIFLUZ (3)


mifluz - C++ library to use and manage inverted indexes


Classes And Commands
See Also


#include <mifluz.h>

main() { Configuration* config = WordContext::Initialize();

WordList* words = new WordList(*config);


delete words;

WordContext::Finish(); }


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 ( version 3.1.14.



reads the configuration file and manages it in memory.


read configuration and setup mifluz context.


abstract class to search and retrieve entries in a WordList object.


search and retrieve entries in a WordListOne object.

  inverted index usage environment.

manage and use an inverted index dictionary.

  inverted index key.
  information on the key structure of the inverted index.

abstract class to manage and use an inverted index file.


manage and use an inverted index file.

  monitoring classes activity.
  inverted index record.
  information on the record structure of the inverted index.
  inverted index occurrence.
  defines a word in term of allowed characters, length etc.

dump the content of an inverted index in Berkeley DB fashion


displays statistics for Berkeley DB environments.


displays statistics for Berkeley DB environments.


dump the dictionnary of an inverted index.


dump the content of an inverted index.


load the content of an inverted index.

  search the content of an inverted index.


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.
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
.See setlocale(3) 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.
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

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)


MIFLUZ_CONFIG file name of configuration file read by WordContext(3). Defaults to ~/.mifluz. or /usr/etc/mifluz.conf


Loic Dachary

The Ht://Dig group


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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