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, int flags=0)
	Open a Database, automatically determining the database backend to use. More...

	Database (int fd, int flags=0)
	Open a single-file Database. 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...

bool	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 std::string &prefix=std::string()) const
	An iterator which runs across all terms with a given prefix. More...

TermIterator	allterms_end (const std::string &=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.

ValueIterator	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.

Xapian::termcount	get_unique_terms (Xapian::docid did) const
	Get the number of unique terms in 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...

void	compact (const std::string &output, unsigned flags=0, int block_size=0)
	Produce a compact version of this database. More...

void	compact (int fd, unsigned flags=0, int block_size=0)
	Produce a compact version of this database. More...

void	compact (const std::string &output, unsigned flags, int block_size, Xapian::Compactor &compactor)
	Produce a compact version of this database. More...

void	compact (int fd, unsigned flags, int block_size, Xapian::Compactor &compactor)
	Produce a compact version of this database. More...

Static Public Member Functions
static size_t	check (const std::string &path, int opts=0, std::ostream *out=NULL)
	Check the integrity of a database or database table. More...

static size_t	check (int fd, int opts=0, std::ostream *out=NULL)
	Check the integrity of a single file 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

InvalidArgumentError	will be thrown if an invalid argument is supplied, for example, an unknown database type.
DatabaseOpeningError	may be thrown if the database cannot be opened (for example, a required file cannot be found).
DatabaseVersionError	may 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,
		int	flags = `0`
	)

explicit

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

Parameters

path	directory that the database is stored in.

Xapian::Database::Database	(	int	fd,
		int	flags = `0`
	)

explicit

Open a single-file Database.

This method opens a single-file Database given a file descriptor open on it. Xapian looks starting at the current file offset, allowing a single file database to be easily embedded within another file.

Parameters

fd	file descriptor for the file. Xapian takes ownership of this and will close it when the database is closed.
flags	Bitwise-or of Xapian::DB_* constants.

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

other The 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

database the database(s) to add.

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

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

Parameters

prefix The prefix to restrict the returned terms to (default: iterate all terms)

static size_t Xapian::Database::check	(	const std::string &	path,
		int	opts = `0`,
		std::ostream *	out = `NULL`
	)

inlinestatic

Check the integrity of a database or database table.

Parameters

path	Path to database or table
opts	Options to use for check
out	std::ostream to write output to (NULL for no output)

static size_t Xapian::Database::check	(	int	fd,
		int	opts = `0`,
		std::ostream *	out = `NULL`
	)

inlinestatic

Check the integrity of a single file database.

Parameters

fd	file descriptor for the database. The current file offset is used, allowing checking a single file database which is embedded within another file. Xapian takes ownership of the file descriptor and will close it before returning.
opts	Options to use for check
out	std::ostream to write output to (NULL for no output)

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.

void Xapian::Database::compact	(	const std::string &	output,
		unsigned	flags = `0`,
		int	block_size = `0`
	)

inline

Produce a compact version of this database.

New 1.3.4. Various methods of the Compactor class were deprecated in 1.3.4.

Parameters

output	Path to write the compact version to. This can be the same as an input if that input is a stub database (in which case the database(s) listed in the stub will be compacted to a new database and then the stub will be atomically updated to point to this new database).
flags	Any of the following combined using bitwise-or (\| in C++): Xapian::DBCOMPACT_NO_RENUMBER By default the document ids will be renumbered the output - currently by applying the same offset to all the document ids in a particular source database. If this flag is specified, then this renumbering doesn't happen, but all the document ids must be unique over all source databases. Currently the ranges of document ids in each source must not overlap either, though this restriction may be removed in the future. Xapian::DBCOMPACT_MULTIPASS If merging more than 3 databases, merge the postlists in multiple passes, which is generally faster but requires more disk space for temporary files. Xapian::DBCOMPACT_SINGLE_FILE Produce a single-file database (only supported for glass currently).
block_size	This specifies the block size (in bytes) for to use for the output. For glass, the block size must be a power of 2 between 2048 and 65536 (inclusive), and the default (also used if an invalid value is passed) is 8192 bytes.

void Xapian::Database::compact	(	int	fd,
		unsigned	flags = `0`,
		int	block_size = `0`
	)

inline

Produce a compact version of this database.

New 1.3.4. Various methods of the Compactor class were deprecated in 1.3.4.

This variant writes a single-file database to the specified file descriptor. Only the glass backend supports such databases, so this form is only supported for this backend.

Parameters

fd	File descriptor to write the compact version to. The descriptor needs to be readable and writable (open with O_RDWR) and seekable. The current file offset is used, allowing compacting to a single file database embedded within another file. Xapian takes ownership of the file descriptor and will close it before returning.
flags	Any of the following combined using bitwise-or (\| in C++): Xapian::DBCOMPACT_NO_RENUMBER By default the document ids will be renumbered the output - currently by applying the same offset to all the document ids in a particular source database. If this flag is specified, then this renumbering doesn't happen, but all the document ids must be unique over all source databases. Currently the ranges of document ids in each source must not overlap either, though this restriction may be removed in the future. Xapian::DBCOMPACT_MULTIPASS If merging more than 3 databases, merge the postlists in multiple passes, which is generally faster but requires more disk space for temporary files. Xapian::DBCOMPACT_SINGLE_FILE Produce a single-file database (only supported for glass currently) - this flag is implied in this form and need not be specified explicitly.
block_size	This specifies the block size (in bytes) for to use for the output. For glass, the block size must be a power of 2 between 2048 and 65536 (inclusive), and the default (also used if an invalid value is passed) is 8192 bytes.

void Xapian::Database::compact	(	const std::string &	output,
		unsigned	flags,
		int	block_size,
		Xapian::Compactor &	compactor
	)

inline

Produce a compact version of this database.

New 1.3.4. Various methods of the Compactor class were deprecated in 1.3.4.

The compactor functor allows handling progress output and specifying how user metadata is merged.

Parameters

output	Path to write the compact version to. This can be the same as an input if that input is a stub database (in which case the database(s) listed in the stub will be compacted to a new database and then the stub will be atomically updated to point to this new database).
flags	Any of the following combined using bitwise-or (\| in C++): Xapian::DBCOMPACT_NO_RENUMBER By default the document ids will be renumbered the output - currently by applying the same offset to all the document ids in a particular source database. If this flag is specified, then this renumbering doesn't happen, but all the document ids must be unique over all source databases. Currently the ranges of document ids in each source must not overlap either, though this restriction may be removed in the future. Xapian::DBCOMPACT_MULTIPASS If merging more than 3 databases, merge the postlists in multiple passes, which is generally faster but requires more disk space for temporary files. Xapian::DBCOMPACT_SINGLE_FILE Produce a single-file database (only supported for glass currently).
block_size	This specifies the block size (in bytes) for to use for the output. For glass, the block size must be a power of 2 between 2048 and 65536 (inclusive), and the default (also used if an invalid value is passed) is 8192 bytes.
compactor	Functor

void Xapian::Database::compact	(	int	fd,
		unsigned	flags,
		int	block_size,
		Xapian::Compactor &	compactor
	)

inline

Produce a compact version of this database.

New 1.3.4. Various methods of the Compactor class were deprecated in 1.3.4.

The compactor functor allows handling progress output and specifying how user metadata is merged.

This variant writes a single-file database to the specified file descriptor. Only the glass backend supports such databases, so this form is only supported for this backend.

Parameters

fd	File descriptor to write the compact version to. The descriptor needs to be readable and writable (open with O_RDWR) and seekable. The current file offset is used, allowing compacting to a single file database embedded within another file. Xapian takes ownership of the file descriptor and will close it before returning.
flags	Any of the following combined using bitwise-or (\| in C++): Xapian::DBCOMPACT_NO_RENUMBER By default the document ids will be renumbered the output - currently by applying the same offset to all the document ids in a particular source database. If this flag is specified, then this renumbering doesn't happen, but all the document ids must be unique over all source databases. Currently the ranges of document ids in each source must not overlap either, though this restriction may be removed in the future. Xapian::DBCOMPACT_MULTIPASS If merging more than 3 databases, merge the postlists in multiple passes, which is generally faster but requires more disk space for temporary files. Xapian::DBCOMPACT_SINGLE_FILE Produce a single-file database (only supported for glass currently) - this flag is implied in this form and need not be specified explicitly.
block_size	This specifies the block size (in bytes) for to use for the output. For glass, the block size must be a power of 2 between 2048 and 65536 (inclusive), and the default (also used if an invalid value is passed) is 8192 bytes.
compactor	Functor

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

tname The 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

did	The document id of the document to retrieve.

Returns: A Xapian::Document object containing the document data

Exceptions

Xapian::DocNotFoundError	The document specified could not be found in the database.
Xapian::InvalidArgumentError	did 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

key	The key of the metadata item to access.

Returns: The retrieved metadata item's value.

Exceptions

Xapian::InvalidArgumentError will 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

word	The potentially misspelled word.
max_edit_distance	Only 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

slot	The value slot to examine.

Exceptions

UnimplementedError The 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

slot	The 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

slot	The value slot to examine.

Exceptions

UnimplementedError The 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

prefix If non-empty, only keys with this prefix are returned.

Exceptions

Xapian::UnimplementedError will 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

other The 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

tname The 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.

bool 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.

Returns: true if the database might have been reopened (if false is returned, the database definitely hasn't been reopened, which applications may find useful when caching results, etc). In Xapian < 1.3.0, this method did not return a value.

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

prefix If 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

term	The 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

tname The 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

did	The document id of the document to iterate terms for.

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

xapian/database.h

Public Member Functions

Static Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation