Public Member Functions | List of all members
Xapian::Database Class Reference

This class is used to access a database, or a group of databases. More...

+ Inheritance diagram for Xapian::Database:

Public Member Functions

void add_database (const Database &database)
 Add an existing database (or group of databases) to those accessed by this object. More...
 
 Database ()
 Create a Database with no databases in.
 
 Database (const std::string &path)
 Open a Database, automatically determining the database backend to use. More...
 
virtual ~Database ()
 Destroy this handle on the database. More...
 
 Database (const Database &other)
 Copying is allowed. More...
 
void operator= (const Database &other)
 Assignment is allowed. More...
 
void reopen ()
 Re-open the database. More...
 
virtual void close ()
 Close the database. More...
 
virtual std::string get_description () const
 Return a string describing this object.
 
PostingIterator postlist_begin (const std::string &tname) const
 An iterator pointing to the start of the postlist for a given term. More...
 
PostingIterator postlist_end (const std::string &) const
 Corresponding end iterator to postlist_begin().
 
TermIterator termlist_begin (Xapian::docid did) const
 An iterator pointing to the start of the termlist for a given document. More...
 
TermIterator termlist_end (Xapian::docid) const
 Corresponding end iterator to termlist_begin().
 
bool has_positions () const
 Does this database have any positional information?
 
PositionIterator positionlist_begin (Xapian::docid did, const std::string &tname) const
 An iterator pointing to the start of the position list for a given term in a given document.
 
PositionIterator positionlist_end (Xapian::docid, const std::string &) const
 Corresponding end iterator to positionlist_begin().
 
TermIterator allterms_begin () const
 An iterator which runs across all terms in the database.
 
TermIterator allterms_end () const
 Corresponding end iterator to allterms_begin().
 
TermIterator allterms_begin (const std::string &prefix) const
 An iterator which runs across all terms with a given prefix. More...
 
TermIterator allterms_end (const std::string &) const
 Corresponding end iterator to allterms_begin(prefix).
 
Xapian::doccount get_doccount () const
 Get the number of documents in the database.
 
Xapian::docid get_lastdocid () const
 Get the highest document id which has been used in the database.
 
Xapian::doclength get_avlength () const
 Get the average length of the documents in the database.
 
Xapian::doccount get_termfreq (const std::string &tname) const
 Get the number of documents in the database indexed by a given term.
 
bool term_exists (const std::string &tname) const
 Check if a given term exists in the database. More...
 
Xapian::termcount get_collection_freq (const std::string &tname) const
 Return the total number of occurrences of the given term. More...
 
Xapian::doccount get_value_freq (Xapian::valueno slot) const
 Return the frequency of a given value slot. More...
 
std::string get_value_lower_bound (Xapian::valueno slot) const
 Get a lower bound on the values stored in the given value slot. More...
 
std::string get_value_upper_bound (Xapian::valueno slot) const
 Get an upper bound on the values stored in the given value slot. More...
 
Xapian::termcount get_doclength_lower_bound () const
 Get a lower bound on the length of a document in this DB. More...
 
Xapian::termcount get_doclength_upper_bound () const
 Get an upper bound on the length of a document in this DB.
 
Xapian::termcount get_wdf_upper_bound (const std::string &term) const
 Get an upper bound on the wdf of term term.
 
ValueIterator valuestream_begin (Xapian::valueno slot) const
 Return an iterator over the value in slot slot for each document.
 
ValueIteratorEnd_ valuestream_end (Xapian::valueno) const
 Return end iterator corresponding to valuestream_begin().
 
Xapian::termcount get_doclength (Xapian::docid did) const
 Get the length of a document.
 
void keep_alive ()
 Send a "keep-alive" to remote databases to stop them timing out. More...
 
Xapian::Document get_document (Xapian::docid did) const
 Get a document from the database, given its document id. More...
 
std::string get_spelling_suggestion (const std::string &word, unsigned max_edit_distance=2) const
 Suggest a spelling correction. More...
 
Xapian::TermIterator spellings_begin () const
 An iterator which returns all the spelling correction targets. More...
 
Xapian::TermIterator spellings_end () const
 Corresponding end iterator to spellings_begin().
 
Xapian::TermIterator synonyms_begin (const std::string &term) const
 An iterator which returns all the synonyms for a given term. More...
 
Xapian::TermIterator synonyms_end (const std::string &) const
 Corresponding end iterator to synonyms_begin(term).
 
Xapian::TermIterator synonym_keys_begin (const std::string &prefix=std::string()) const
 An iterator which returns all terms which have synonyms. More...
 
Xapian::TermIterator synonym_keys_end (const std::string &=std::string()) const
 Corresponding end iterator to synonym_keys_begin(prefix).
 
std::string get_metadata (const std::string &key) const
 Get the user-specified metadata associated with a given key. More...
 
Xapian::TermIterator metadata_keys_begin (const std::string &prefix=std::string()) const
 An iterator which returns all user-specified metadata keys. More...
 
Xapian::TermIterator metadata_keys_end (const std::string &=std::string()) const
 Corresponding end iterator to metadata_keys_begin().
 
std::string get_uuid () const
 Get a UUID for the database. More...
 

Detailed Description

This class is used to access a database, or a group of databases.

For searching, this class is used in conjunction with an Enquire object.

Exceptions
InvalidArgumentErrorwill be thrown if an invalid argument is supplied, for example, an unknown database type.
DatabaseOpeningErrormay be thrown if the database cannot be opened (for example, a required file cannot be found).
DatabaseVersionErrormay be thrown if the database is in an unsupported format (for example, created by a newer version of Xapian which uses an incompatible format).

Constructor & Destructor Documentation

Xapian::Database::Database ( const std::string &  path)
explicit

Open a Database, automatically determining the database backend to use.

Parameters
pathdirectory that the database is stored in.
virtual Xapian::Database::~Database ( )
virtual

Destroy this handle on the database.

If there are no copies of this object remaining, the database(s) will be closed.

Xapian::Database::Database ( const Database other)

Copying is allowed.

The internals are reference counted, so copying is cheap.

Parameters
otherThe object to copy.

Member Function Documentation

void Xapian::Database::add_database ( const Database database)

Add an existing database (or group of databases) to those accessed by this object.

Parameters
databasethe database(s) to add.
TermIterator Xapian::Database::allterms_begin ( const std::string &  prefix) const

An iterator which runs across all terms with a given prefix.

This is functionally similar to getting an iterator with allterms_begin() and then calling skip_to(prefix) on that iterator to move to the start of the prefix, but is more convenient (because it detects the end of the prefixed terms), and may be more efficient than simply calling skip_to() after opening the iterator, particularly for remote databases.

Parameters
prefixThe prefix to restrict the returned terms to.
virtual void Xapian::Database::close ( )
virtual

Close the database.

This closes the database and closes all its file handles.

For a WritableDatabase, if a transaction is active it will be aborted, while if no transaction is active commit() will be implicitly called. Also the write lock is released.

Closing a database cannot be undone - in particular, calling reopen() after close() will not reopen it, but will instead throw a Xapian::DatabaseError exception.

Calling close() again on a database which has already been closed has no effect (and doesn't raise an exception).

After close() has been called, calls to other methods of the database, and to methods of other objects associated with the database, will either:

  • behave exactly as they would have done if the database had not been closed (this can only happen if all the required data is cached)
  • raise a Xapian::DatabaseError exception indicating that the database is closed.

The reason for this behaviour is that otherwise we'd have to check that the database is still open on every method call on every object associated with a Database, when in many cases they are working on data which has already been loaded and so they are able to just behave correctly.

This method was added in Xapian 1.1.0.

Xapian::termcount Xapian::Database::get_collection_freq ( const std::string &  tname) const

Return the total number of occurrences of the given term.

This is the sum of the number of occurrences of the term in each document it indexes: i.e., the sum of the within document frequencies of the term.

Parameters
tnameThe term whose collection frequency is being requested.
Xapian::termcount Xapian::Database::get_doclength_lower_bound ( ) const

Get a lower bound on the length of a document in this DB.

This bound does not include any zero-length documents.

Xapian::Document Xapian::Database::get_document ( Xapian::docid  did) const

Get a document from the database, given its document id.

This method returns a Xapian::Document object which provides the information about a document.

Parameters
didThe document id of the document to retrieve.
Returns
A Xapian::Document object containing the document data
Exceptions
Xapian::DocNotFoundErrorThe document specified could not be found in the database.
Xapian::InvalidArgumentErrordid was 0, which is not a valid document id.
std::string Xapian::Database::get_metadata ( const std::string &  key) const

Get the user-specified metadata associated with a given key.

User-specified metadata allows you to store arbitrary information in the form of (key,tag) pairs. See WritableDatabase::set_metadata() for more information.

When invoked on a Xapian::Database object representing multiple databases, currently only the metadata for the first is considered but this behaviour may change in the future.

If there is no piece of metadata associated with the specified key, an empty string is returned (this applies even for backends which don't support metadata).

Empty keys are not valid, and specifying one will cause an exception.

Parameters
keyThe key of the metadata item to access.
Returns
The retrieved metadata item's value.
Exceptions
Xapian::InvalidArgumentErrorwill be thrown if the key supplied is empty.
std::string Xapian::Database::get_spelling_suggestion ( const std::string &  word,
unsigned  max_edit_distance = 2 
) const

Suggest a spelling correction.

Parameters
wordThe potentially misspelled word.
max_edit_distanceOnly consider words which are at most max_edit_distance edits from word. An edit is a character insertion, deletion, or the transposition of two adjacent characters (default is 2).
std::string Xapian::Database::get_uuid ( ) const

Get a UUID for the database.

The UUID will persist for the lifetime of the database.

Replicas (eg, made with the replication protocol, or by copying all the database files) will have the same UUID. However, copies (made with copydatabase, or xapian-compact) will have different UUIDs.

If the backend does not support UUIDs or this database has no subdatabases, the UUID will be empty.

If this database has multiple sub-databases, the UUID string will contain the UUIDs of all the sub-databases.

Xapian::doccount Xapian::Database::get_value_freq ( Xapian::valueno  slot) const

Return the frequency of a given value slot.

This is the number of documents which have a (non-empty) value stored in the slot.

Parameters
slotThe value slot to examine.
Exceptions
UnimplementedErrorThe frequency of the value isn't available for this database type.
std::string Xapian::Database::get_value_lower_bound ( Xapian::valueno  slot) const

Get a lower bound on the values stored in the given value slot.

If there are no values stored in the given value slot, this will return an empty string.

If the lower bound isn't available for the given database type, this will return the lowest possible bound - the empty string.

Parameters
slotThe value slot to examine.
std::string Xapian::Database::get_value_upper_bound ( Xapian::valueno  slot) const

Get an upper bound on the values stored in the given value slot.

If there are no values stored in the given value slot, this will return an empty string.

Parameters
slotThe value slot to examine.
Exceptions
UnimplementedErrorThe upper bound of the values isn't available for this database type.
void Xapian::Database::keep_alive ( )

Send a "keep-alive" to remote databases to stop them timing out.

Has no effect on non-remote databases.

Xapian::TermIterator Xapian::Database::metadata_keys_begin ( const std::string &  prefix = std::string()) const

An iterator which returns all user-specified metadata keys.

When invoked on a Xapian::Database object representing multiple databases, currently only the metadata for the first is considered but this behaviour may change in the future.

If the backend doesn't support metadata, then this method returns an iterator which compares equal to that returned by metadata_keys_end().

Parameters
prefixIf non-empty, only keys with this prefix are returned.
Exceptions
Xapian::UnimplementedErrorwill be thrown if the backend implements user-specified metadata, but doesn't implement iterating its keys (currently this happens for the InMemory backend).
void Xapian::Database::operator= ( const Database other)

Assignment is allowed.

The internals are reference counted, so assignment is cheap.

Parameters
otherThe object to copy.
PostingIterator Xapian::Database::postlist_begin ( const std::string &  tname) const

An iterator pointing to the start of the postlist for a given term.

Parameters
tnameThe termname to iterate postings for. If the term name is the empty string, the iterator returned will list all the documents in the database. Such an iterator will always return a WDF value of 1, since there is no obvious meaning for this quantity in this case.
void Xapian::Database::reopen ( )

Re-open the database.

This re-opens the database(s) to the latest available version(s). It can be used either to make sure the latest results are returned, or to recover from a Xapian::DatabaseModifiedError.

Calling reopen() on a database which has been closed (with close()) will always raise a Xapian::DatabaseError.

Xapian::TermIterator Xapian::Database::spellings_begin ( ) const

An iterator which returns all the spelling correction targets.

This returns all the words which are considered as targets for the spelling correction algorithm. The frequency of each word is available as the term frequency of each entry in the returned iterator.

Xapian::TermIterator Xapian::Database::synonym_keys_begin ( const std::string &  prefix = std::string()) const

An iterator which returns all terms which have synonyms.

Parameters
prefixIf non-empty, only terms with this prefix are returned.
Xapian::TermIterator Xapian::Database::synonyms_begin ( const std::string &  term) const

An iterator which returns all the synonyms for a given term.

Parameters
termThe term to return synonyms for.
bool Xapian::Database::term_exists ( const std::string &  tname) const

Check if a given term exists in the database.

Parameters
tnameThe term to test the existence of.
Returns
true if and only if the term exists in the database. This is the same as (get_termfreq(tname) != 0), but will often be more efficient.
TermIterator Xapian::Database::termlist_begin ( Xapian::docid  did) const

An iterator pointing to the start of the termlist for a given document.

Parameters
didThe document id of the document to iterate terms for.

The documentation for this class was generated from the following file:

Documentation for Xapian (version 1.2.21).
Generated on Thu May 21 2015 by Doxygen 1.8.5.