Odeum is the API which handles an inverted index. An inverted index is a data structure to retrieve a
list of some documents that include one of words which were extracted from a population of documents. It
is easy to realize a full-text search system with an inverted index. Odeum provides an abstract data
structure which consists of words and attributes of a document. It is used when an application stores a
document into a database and when an application retrieves some documents from a database.
Odeum does not provide methods to extract the text from the original data of a document. It should be
implemented by applications. Although Odeum provides utilities to extract words from a text, it is
oriented to such languages whose words are separated with space characters as English. If an application
handles such languages which need morphological analysis or N-gram analysis as Japanese, or if an
application perform more such rarefied analysis of natural languages as stemming, its own analyzing
method can be adopted. Result of search is expressed as an array contains elements which are structures
composed of the ID number of documents and its score. In order to search with two or more words, Odeum
provides utilities of set operations.
Odeum is implemented, based on Curia, Cabin, and Villa. Odeum creates a database with a directory name.
Some databases of Curia and Villa are placed in the specified directory. For example, `casket/docs',
`casket/index', and `casket/rdocs' are created in the case that a database directory named as `casket'.
`docs' is a database directory of Curia. The key of each record is the ID number of a document, and the
value is such attributes as URI. `index' is a database directory of Curia. The key of each record is
the normalized form of a word, and the value is an array whose element is a pair of the ID number of a
document including the word and its score. `rdocs' is a database file of Villa. The key of each record
is the URI of a document, and the value is its ID number.
In order to use Odeum, you should include `depot.h', `cabin.h', `odeum.h' and `stdlib.h' in the source
files. Usually, the following description will be near the beginning of a source file.
#include<depot.h>#include<cabin.h>#include<odeum.h>#include<stdlib.h>
A pointer to `ODEUM' is used as a database handle. A database handle is opened with the function
`odopen' and closed with `odclose'. You should not refer directly to any member of the handle. If a
fatal error occurs in a database, any access method via the handle except `odclose' will not work and
return error status. Although a process is allowed to use multiple database handles at the same time,
handles of the same database file should not be used.
A pointer to `ODDOC' is used as a document handle. A document handle is opened with the function
`oddocopen' and closed with `oddocclose'. You should not refer directly to any member of the handle. A
document consists of attributes and words. Each word is expressed as a pair of a normalized form and a
appearance form.
Odeum also assign the external variable `dpecode' with the error code. The function `dperrmsg' is used in
order to get the message of the error code.
Structures of `ODPAIR' type is used in order to handle results of search.
typedefstruct{intid;intscore;}ODPAIR;
`id' specifies the ID number of a document. `score' specifies the score calculated from the
number of searching words in the document.
The function `odopen' is used in order to get a database handle.
ODEUM*odopen(constchar*name,intomode);
`name' specifies the name of a database directory. `omode' specifies the connection mode:
`OD_OWRITER' as a writer, `OD_OREADER' as a reader. If the mode is `OD_OWRITER', the following
may be added by bitwise or: `OD_OCREAT', which means it creates a new database if not exist,
`OD_OTRUNC', which means it creates a new database regardless if one exists. Both of `OD_OREADER'
and `OD_OWRITER' can be added to by bitwise or: `OD_ONOLCK', which means it opens a database
directory without file locking, or `OD_OLCKNB', which means locking is performed without blocking.
The return value is the database handle or `NULL' if it is not successful. While connecting as a
writer, an exclusive lock is invoked to the database directory. While connecting as a reader, a
shared lock is invoked to the database directory. The thread blocks until the lock is achieved.
If `OD_ONOLCK' is used, the application is responsible for exclusion control.
The function `odclose' is used in order to close a database handle.
intodclose(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is true, else, it is false.
Because the region of a closed handle is released, it becomes impossible to use the handle.
Updating a database is assured to be written when the handle is closed. If a writer opens a
database but does not close it appropriately, the database will be broken.
The function `odput' is used in order to store a document.
intodput(ODEUM*odeum,constODDOC*doc,intwmax,intover);
`odeum' specifies a database handle connected as a writer. `doc' specifies a document handle.
`wmax' specifies the max number of words to be stored in the document database. If it is
negative, the number is unlimited. `over' specifies whether the data of the duplicated document
is overwritten or not. If it is false and the URI of the document is duplicated, the function
returns as an error. If successful, the return value is true, else, it is false.
The function `odout' is used in order to delete a document specified by a URI.
intodout(ODEUM*odeum,constchar*uri);
`odeum' specifies a database handle connected as a writer. `uri' specifies the string of the URI
of a document. If successful, the return value is true, else, it is false. False is returned
when no document corresponds to the specified URI.
The function `odoutbyid' is used in order to delete a document specified by an ID number.
intodoutbyid(ODEUM*odeum,intid);
`odeum' specifies a database handle connected as a writer. `id' specifies the ID number of a
document. If successful, the return value is true, else, it is false. False is returned when no
document corresponds to the specified ID number.
The function `odget' is used in order to retrieve a document specified by a URI.
ODDOC*odget(ODEUM*odeum,constchar*uri);
`odeum' specifies a database handle. `uri' specifies the string of the URI of a document. If
successful, the return value is the handle of the corresponding document, else, it is `NULL'.
`NULL' is returned when no document corresponds to the specified URI. Because the handle of the
return value is opened with the function `oddocopen', it should be closed with the function
`oddocclose'.
The function `odgetbyid' is used in order to retrieve a document by an ID number.
ODDOC*odgetbyid(ODEUM*odeum,intid);
`odeum' specifies a database handle. `id' specifies the ID number of a document. If successful,
the return value is the handle of the corresponding document, else, it is `NULL'. `NULL' is
returned when no document corresponds to the specified ID number. Because the handle of the
return value is opened with the function `oddocopen', it should be closed with the function
`oddocclose'.
The function `odgetidbyuri' is used in order to retrieve the ID of the document specified by a URI.
intodgetidbyuri(ODEUM*odeum,constchar*uri);
`odeum' specifies a database handle. `uri' specifies the string the URI of a document. If
successful, the return value is the ID number of the document, else, it is -1. -1 is returned
when no document corresponds to the specified URI.
The function `odcheck' is used in order to check whether the document specified by an ID number exists.
intodcheck(ODEUM*odeum,intid);
`odeum' specifies a database handle. `id' specifies the ID number of a document. The return
value is true if the document exists, else, it is false.
The function `odsearch' is used in order to search the inverted index for documents including a
particular word.
ODPAIR*odsearch(ODEUM*odeum,constchar*word,intmax,int*np);
`odeum' specifies a database handle. `word' specifies a searching word. `max' specifies the max
number of documents to be retrieve. `np' specifies the pointer to a variable to which the number
of the elements of the return value is assigned. If successful, the return value is the pointer
to an array, else, it is `NULL'. Each element of the array is a pair of the ID number and the
score of a document, and sorted in descending order of their scores. Even if no document
corresponds to the specified word, it is not error but returns an dummy array. Because the region
of the return value is allocated with the `malloc' call, it should be released with the `free'
call if it is no longer in use. Note that each element of the array of the return value can be
data of a deleted document.
The function `odsearchnum' is used in order to get the number of documents including a word.
intodsearchdnum(ODEUM*odeum,constchar*word);
`odeum' specifies a database handle. `word' specifies a searching word. If successful, the
return value is the number of documents including the word, else, it is -1. Because this function
does not read the entity of the inverted index, it is faster than `odsearch'.
The function `oditerinit' is used in order to initialize the iterator of a database handle.
intoditerinit(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is true, else, it is false.
The iterator is used in order to access every document stored in a database.
The function `oditernext' is used in order to get the next key of the iterator.
ODDOC*oditernext(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the handle of the next
document, else, it is `NULL'. `NULL' is returned when no document is to be get out of the
iterator. It is possible to access every document by iteration of calling this function.
However, it is not assured if updating the database is occurred while the iteration. Besides, the
order of this traversal access method is arbitrary, so it is not assured that the order of string
matches the one of the traversal access. Because the handle of the return value is opened with
the function `oddocopen', it should be closed with the function `oddocclose'.
The function `odsync' is used in order to synchronize updating contents with the files and the devices.
intodsync(ODEUM*odeum);
`odeum' specifies a database handle connected as a writer. If successful, the return value is
true, else, it is false. This function is useful when another process uses the connected database
directory.
The function `odoptimize' is used in order to optimize a database.
intodoptimize(ODEUM*odeum);
`odeum' specifies a database handle connected as a writer. If successful, the return value is
true, else, it is false. Elements of the deleted documents in the inverted index are purged.
The function `odname' is used in order to get the name of a database.
char*odname(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the pointer to the region
of the name of the database, else, it is `NULL'. Because the region of the return value is
allocated with the `malloc' call, it should be released with the `free' call if it is no longer in
use.
The function `odfsiz' is used in order to get the total size of database files.
doubleodfsiz(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the total size of the
database files, else, it is -1.0.
The function `odbnum' is used in order to get the total number of the elements of the bucket arrays in
the inverted index.
intodbnum(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the total number of the
elements of the bucket arrays, else, it is -1.
The function `odbusenum' is used in order to get the total number of the used elements of the bucket
arrays in the inverted index.
intodbusenum(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the total number of the
used elements of the bucket arrays, else, it is -1.
The function `oddnum' is used in order to get the number of the documents stored in a database.
intoddnum(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the number of the
documents stored in the database, else, it is -1.
The function `odwnum' is used in order to get the number of the words stored in a database.
intodwnum(ODEUM*odeum);
`odeum' specifies a database handle. If successful, the return value is the number of the words
stored in the database, else, it is -1. Because of the I/O buffer, the return value may be less
than the hard number.
The function `odwritable' is used in order to check whether a database handle is a writer or not.
intodwritable(ODEUM*odeum);
`odeum' specifies a database handle. The return value is true if the handle is a writer, false if
not.
The function `odfatalerror' is used in order to check whether a database has a fatal error or not.
intodfatalerror(ODEUM*odeum);
`odeum' specifies a database handle. The return value is true if the database has a fatal error,
false if not.
The function `odinode' is used in order to get the inode number of a database directory.
intodinode(ODEUM*odeum);
`odeum' specifies a database handle. The return value is the inode number of the database
directory.
The function `odmtime' is used in order to get the last modified time of a database.
time_todmtime(ODEUM*odeum);
`odeum' specifies a database handle. The return value is the last modified time of the database.
The function `odmerge' is used in order to merge plural database directories.
intodmerge(constchar*name,constCBLIST*elemnames);
`name' specifies the name of a database directory to create. `elemnames' specifies a list of
names of element databases. If successful, the return value is true, else, it is false. If two
or more documents which have the same URL come in, the first one is adopted and the others are
ignored.
The function `odremove' is used in order to remove a database directory.
intodremove(constchar*name);
`name' specifies the name of a database directory. If successful, the return value is true, else,
it is false. A database directory can contain databases of other APIs of QDBM, they are also
removed by this function.
The function `oddocopen' is used in order to get a document handle.
ODDOC*oddocopen(constchar*uri);
`uri' specifies the URI of a document. The return value is a document handle. The ID number of a
new document is not defined. It is defined when the document is stored in a database.
The function `oddocclose' is used in order to close a document handle.
voidoddocclose(ODDOC*doc);
`doc' specifies a document handle. Because the region of a closed handle is released, it becomes
impossible to use the handle.
The function `oddocaddattr' is used in order to add an attribute to a document.
voidoddocaddattr(ODDOC*doc,constchar*name,constchar*value);
`doc' specifies a document handle. `name' specifies the string of the name of an attribute.
`value' specifies the string of the value of the attribute.
The function `oddocaddword' is used in order to add a word to a document.
voidoddocaddword(ODDOC*doc,constchar*normal,constchar*asis);
`doc' specifies a document handle. `normal' specifies the string of the normalized form of a
word. Normalized forms are treated as keys of the inverted index. If the normalized form of a
word is an empty string, the word is not reflected in the inverted index. `asis' specifies the
string of the appearance form of the word. Appearance forms are used after the document is
retrieved by an application.
The function `oddocid' is used in order to get the ID number of a document.
intoddocid(constODDOC*doc);
`doc' specifies a document handle. The return value is the ID number of a document.
The function `oddocuri' is used in order to get the URI of a document.
constchar*oddocuri(constODDOC*doc);
`doc' specifies a document handle. The return value is the string of the URI of a document.
The function `oddocgetattr' is used in order to get the value of an attribute of a document.
constchar*oddocgetattr(constODDOC*doc,constchar*name);
`doc' specifies a document handle. `name' specifies the string of the name of an attribute. The
return value is the string of the value of the attribute, or `NULL' if no attribute corresponds.
The function `oddocnwords' is used in order to get the list handle contains words in normalized form of a
document.
constCBLIST*oddocnwords(constODDOC*doc);
`doc' specifies a document handle. The return value is the list handle contains words in
normalized form.
The function `oddocawords' is used in order to get the list handle contains words in appearance form of a
document.
constCBLIST*oddocawords(constODDOC*doc);
`doc' specifies a document handle. The return value is the list handle contains words in
appearance form.
The function `oddocscores' is used in order to get the map handle contains keywords in normalized form
and their scores.
CBMAP*oddocscores(constODDOC*doc,intmax,ODEUM*odeum);
`doc' specifies a document handle. `max' specifies the max number of keywords to get. `odeum'
specifies a database handle with which the IDF for weighting is calculate. If it is `NULL', it is
not used. The return value is the map handle contains keywords and their scores. Scores are
expressed as decimal strings. Because the handle of the return value is opened with the function
`cbmapopen', it should be closed with the function `cbmapclose' if it is no longer in use.
The function `odbreaktext' is used in order to break a text into words in appearance form.
CBLIST*odbreaktext(constchar*text);
`text' specifies the string of a text. The return value is the list handle contains words in
appearance form. Words are separated with space characters and such delimiters as period, comma
and so on. Because the handle of the return value is opened with the function `cblistopen', it
should be closed with the function `cblistclose' if it is no longer in use.
The function `odnormalizeword' is used in order to make the normalized form of a word.
char*odnormalizeword(constchar*asis);
`asis' specifies the string of the appearance form of a word. The return value is is the string
of the normalized form of the word. Alphabets of the ASCII code are unified into lower cases.
Words composed of only delimiters are treated as empty strings. Because the region of the return
value is allocated with the `malloc' call, it should be released with the `free' call if it is no
longer in use.
The function `odpairsand' is used in order to get the common elements of two sets of documents.
ODPAIR*odpairsand(ODPAIR*apairs,intanum,ODPAIR*bpairs,intbnum,int*np);
`apairs' specifies the pointer to the former document array. `anum' specifies the number of the
elements of the former document array. `bpairs' specifies the pointer to the latter document
array. `bnum' specifies the number of the elements of the latter document array. `np' specifies
the pointer to a variable to which the number of the elements of the return value is assigned.
The return value is the pointer to a new document array whose elements commonly belong to the
specified two sets. Elements of the array are sorted in descending order of their scores.
Because the region of the return value is allocated with the `malloc' call, it should be released
with the `free' call if it is no longer in use.
The function `odpairsor' is used in order to get the sum of elements of two sets of documents.
ODPAIR*odpairsor(ODPAIR*apairs,intanum,ODPAIR*bpairs,intbnum,int*np);
`apairs' specifies the pointer to the former document array. `anum' specifies the number of the
elements of the former document array. `bpairs' specifies the pointer to the latter document
array. `bnum' specifies the number of the elements of the latter document array. `np' specifies
the pointer to a variable to which the number of the elements of the return value is assigned.
The return value is the pointer to a new document array whose elements belong to both or either of
the specified two sets. Elements of the array are sorted in descending order of their scores.
Because the region of the return value is allocated with the `malloc' call, it should be released
with the `free' call if it is no longer in use.
The function `odpairsnotand' is used in order to get the difference set of documents.
ODPAIR*odpairsnotand(ODPAIR*apairs,intanum,ODPAIR*bpairs,intbnum,int*np);
`apairs' specifies the pointer to the former document array. `anum' specifies the number of the
elements of the former document array. `bpairs' specifies the pointer to the latter document
array of the sum of elements. `bnum' specifies the number of the elements of the latter document
array. `np' specifies the pointer to a variable to which the number of the elements of the return
value is assigned. The return value is the pointer to a new document array whose elements belong
to the former set but not to the latter set. Elements of the array are sorted in descending order
of their scores. Because the region of the return value is allocated with the `malloc' call, it
should be released with the `free' call if it is no longer in use.
The function `odpairssort' is used in order to sort a set of documents in descending order of scores.
voidodpairssort(ODPAIR*pairs,intpnum);
`pairs' specifies the pointer to a document array. `pnum' specifies the number of the elements of
the document array.
The function `odlogarithm' is used in order to get the natural logarithm of a number.
doubleodlogarithm(doublex);
`x' specifies a number. The return value is the natural logarithm of the number. If the number
is equal to or less than 1.0, the return value is 0.0. This function is useful when an
application calculates the IDF of search results.
The function `odvectorcosine' is used in order to get the cosine of the angle of two vectors.
doubleodvectorcosine(constint*avec,constint*bvec,intvnum);
`avec' specifies the pointer to one array of numbers. `bvec' specifies the pointer to the other
array of numbers. `vnum' specifies the number of elements of each array. The return value is the
cosine of the angle of two vectors. This function is useful when an application calculates
similarity of documents.
The function `odsettuning' is used in order to set the global tuning parameters.
voidodsettuning(intibnum,intidnum,intcbnum,intcsiz);
`ibnum' specifies the number of buckets for inverted indexes. `idnum' specifies the division
number of inverted index. `cbnum' specifies the number of buckets for dirty buffers. `csiz'
specifies the maximum bytes to use memory for dirty buffers. The default setting is equivalent to
`odsettuning(32749, 7, 262139, 8388608)'. This function should be called before opening a handle.
The function `odanalyzetext' is used in order to break a text into words and store appearance forms and
normalized form into lists.
voidodanalyzetext(ODEUM*odeum,constchar*text,CBLIST*awords,CBLIST*nwords);
`odeum' specifies a database handle. `text' specifies the string of a text. `awords' specifies a
list handle into which appearance form is store. `nwords' specifies a list handle into which
normalized form is store. If it is `NULL', it is ignored. Words are separated with space
characters and such delimiters as period, comma and so on.
The function `odsetcharclass' is used in order to set the classes of characters used by `odanalyzetext'.
voidodsetcharclass(ODEUM*odeum,constchar*spacechars,constchar*delimchars,constchar*gluechars);
`odeum' specifies a database handle. `spacechars' spacifies a string contains space characters.
`delimchars' spacifies a string contains delimiter characters. `gluechars' spacifies a string
contains glue characters.
The function `odquery' is used in order to query a database using a small boolean query language.
ODPAIR*odquery(ODEUM*odeum,constchar*query,int*np,CBLIST*errors);
`odeum' specifies a database handle. 'query' specifies the text of the query. `np' specifies the
pointer to a variable to which the number of the elements of the return value is assigned.
`errors' specifies a list handle into which error messages are stored. If it is `NULL', it is
ignored. If successful, the return value is the pointer to an array, else, it is `NULL'. Each
element of the array is a pair of the ID number and the score of a document, and sorted in
descending order of their scores. Even if no document corresponds to the specified condition, it
is not error but returns an dummy array. Because the region of the return value is allocated with
the `malloc' call, it should be released with the `free' call if it is no longer in use. Note
that each element of the array of the return value can be data of a deleted document.
If QDBM was built with POSIX thread enabled, the global variable `dpecode' is treated as thread specific
data, and functions of Odeum are reentrant. In that case, they are thread-safe as long as a handle is
not accessed by threads at the same time, on the assumption that `errno', `malloc', and so on are
thread-safe.
If QDBM was built with ZLIB enabled, records in the database for document attributes are compressed. In
that case, the size of the database is reduced to 30% or less. Thus, you should enable ZLIB if you use
Odeum. A database of Odeum created without ZLIB enabled is not available on environment with ZLIB
enabled, and vice versa. If ZLIB was not enabled but LZO, LZO is used instead.
The query language of the function `odquery' is a basic language following this grammar:
expr ::= subexpr ( op subexpr )*
subexpr ::= WORD
subexpr ::= LPAREN expr RPAREN
Operators are "&" (AND), "|" (OR), and "!" (NOTAND). You can use parenthesis to group sub-expressions
together in order to change order of operations. The given query is broken up using the function
`odanalyzetext', so if you want to specify different text breaking rules, then make sure that you at
least set "&", "|", "!", "(", and ")" to be delimiter characters. Consecutive words are treated as
having an implicit "&" operator between them, so "zed shaw" is actually "zed & shaw".
The encoding of the query text should be the same with the encoding of target documents. Moreover, each
of space characters, delimiter characters, and glue characters should be single byte.
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