Database Module

This XQuery Module contains functions for processing databases from within XQuery. Existing databases can be opened and listed, its contents can be directly accessed, documents can be added to and removed, etc. All functions are introduced with the db: prefix, which is linked to the statically declared http://basex.org/modules/db namespace.

Conventions

All functions in this module are assigned to the http://basex.org/modules/db namespace, which is statically bound to the db prefix.
All errors are assigned to the http://basex.org/errors namespace, which is statically bound to the bxerr prefix.

Database Nodes

Many function signatures in this and other modules share $db as argument to reference an existing database. The argument may either be a string, denoting the name of the addressed database, or a single node from an already opened database. The following errors may be raised by these functions:

• BXDB0001 is raised if $db references an XML node that is not stored in a database, or is no database fragment.
• BXDB0002 is raised if the addressed database cannot be opened.

Last not but least, the argument may also reference a BaseX-specific database fragment. All XML fragments can be converted to database fragments by applying the transform expression on an XML fragment:

copy $c := element hello { 'world' }
modify ()
return db:text($c, 'world')

General Functions

db:info

Signatures	db:info($db as item()) as element(Database)
Summary	Returns meta information on the database specified by $db.

db:list

Signatures	db:list() as xs:string* db:list($db as item()) as xs:string* db:list($db as item(), $path as xs:string) as xs:string*
Summary	Returns an xs:string sequence with the names of all databases. If $db is specified, all documents and raw files of the specified database are returned. The list of resources can be further restricted by the $path argument.
Examples	db:list("docs") returns the names of all documents from the database named docs.

db:list-details

Signatures	db:list-details() as element(database)* db:list-details($db as item()) as element(resource)* db:list-details($db as item(), $path as xs:string) as element(resource)*
Summary	Returns an element sequence with the names of all databases together with their database path, the number of stored resources and the date of modification. If $db is specified, all documents and raw files of the specified database together with their content-type, the modification date and the resource type are returned. The list of resources can be further restricted by the $path argument.
Examples	db:list-details("docs") returns the names plus additional data of all documents from the database named docs.

db:open

Signatures	db:open($db as item()) as document-node()* db:open($db as item(), $path as xs:string) as document-node()*
Summary	Returns a sequence with all document nodes contained in the database specified by $db. The document nodes to be returned can be restricted by the $path argument.
Examples	db:open("docs") returns all documents from the database named docs. db:open("docs", "one") returns all documents from the database named docs in the subpath one.

db:open-id

Signatures	db:open-id($db as item(), $id as xs:integer) as node()
Summary	Opens the database specified by $db and returns the node with the specified $id value. Each database node has a persistent id, which remains valid after update operations. If no updates are performed, the pre value can be requested, which provides access to database nodes in constant time.
Errors	BXDB0009 is raised if the specified id value does not exist in the database.

db:open-pre

Signatures	db:open-pre($db as item(), $pre as xs:integer) as node()
Summary	Opens the database specified by $db and returns the node with the specified $pre value. The pre value provides access to a database node in constant time, but it is transient, i.e., it may change when database updates are performed.
Errors	BXDB0009 is raised if the specified pre value does not exist in the database.
Examples	db:open-pre("docs", 0) returns the first database node from the database named docs.

db:system

Signatures	db:system() as element(system)
Summary	Returns information on the database system, such as the database path and current database settings.

Read Operations

db:attribute

Signatures	db:attribute($db as item(), $string as item()) as attribute()* db:attribute($db as item(), $string as item(), $attname as xs:string) as attribute()*
Summary	Returns all attribute nodes of the database specified by $db that have $string as string value. If available, the value index is used to speed up evaluation. If $attname is specified, the resulting attribute nodes are filtered by their attribute name.
Examples	db:attribute("DB", "QUERY", "id")/.. returns the parents of all id attribute nodes of the database DB that have QUERY as string value.

db:attribute-range

Signatures	db:attribute-range($db as item(), $min as xs:string, $max as xs:string) as text()* db:attribute-range($db as item(), $min as xs:string, $max as xs:string, $attname as xs:string) as attribute()*
Summary	Returns all attributes of the database specified by $db, the string values of which are larger than or equal to $min and smaller than or equal to $max. If available, the value index is used to speed up evaluation.
Examples	db:attribute-range("DB", "id456", "id473", 'id') returns all @id attributes of the database DB that have a string value in between id456 and id473.

db:fulltext

Signatures	db:fulltext($db as item(), $terms as xs:string) as text()*
Summary	Returns all text nodes from the full-text index of the database specified by $db that contain the text specified as $terms. The options used for building the full-text will also be applied to the search terms. As an example, if the index terms have been stemmed, the search string will be stemmed as well.
Errors	BXDB0004 is raised if the full-text index is not available.
Examples	db:fulltext("DB", "QUERY") returns all text nodes of the database DB that contain the string QUERY.

db:node-id

Signatures	db:node-id($nodes as node()*) as xs:integer*
Summary	Returns the id values of all $nodes of the database specified by $db. Each database node has a persistent id, which remains valid after update operations. If no updates are performed, the pre value can be requested, which provides access to database nodes in constant time.

db:node-pre

Signatures	db:node-pre($nodes as node()*) as xs:integer*
Summary	Returns the pre values of all $nodes of the database specified by $db. The pre value provides access to a database node in constant time, but it is transient, i.e., it may change when database updates are performed.
Examples	db:node-pre(doc("input")) returns 0 if the database input contains a single document.

db:retrieve

Signatures	db:retrieve($db as item(), $path as xs:string) as xs:base64Binary
Summary	Returns a binary database resource addressed by $db and $path.
Errors	BXDB0003 is raised if the databse is not persistent (stored on disk). FODC0002 is raised if the addressed resource cannot be retrieved. FODC0007 is raised if the specified path is invalid.
Examples	declare option output:method 'raw'; db:retrieve("DB", "music/01.mp3") returns the specified audio file as raw data.

db:text

Signatures	db:text($db as item(), $string as item()) as text()*
Summary	Returns all text nodes of the database specified by $db that have $string as their string value. If available, the value index is used to speed up evaluation.
Examples	db:text("DB", "QUERY")/.. returns the parents of all text nodes of the database DB that match the string QUERY.

db:text-range

Signatures	db:text-range($db as item(), $min as xs:string, $max as xs:string) as text()*
Summary	Returns all text nodes of the database specified by $db that are located in between the $min and $max strings. If available, the value index is used to speed up evaluation.
Examples	db:text-range("DB", "2000", "2001") returns all text nodes of the database DB that are found in between 2000 and 2001.

Updates

All functions in this section are treated as updating: they are not immediately executed, but queued on a pending update list, which is processed after the actual query has been evaluated. The XQuery Update page gives more insight into the relevant concepts.

db:add

Signatures	db:add($db as item(), $input as item()) as empty-sequence() db:add($db as item(), $input as item(), $path as xs:string) as empty-sequence()
Summary	Adds documents specified by $input to the database $db and the specified $path.
Errors	FODC0002 is raised if $input is a string representing a path, which cannot be read. FOUP0001 is raised if $input is neither string nor a document node.
Examples	db:add("DB", "/home/dir/doc.xml") adds the file /home/dir/doc.xml to the database DB. db:add("DB", "<a/>", "doc.xml") adds a document with content <a/> to the database DB under the name doc.xml. db:add("DB", document { <a/> }, "doc.xml") adds the document node to the database DB under the name doc.xml. db:add("DB", "/home/dir", "docs/dir") adds all documents in /home/dir to the database DB under the path docs/dir.

db:delete

Signatures	db:delete($db as item(), $path as xs:string) as empty-sequence()
Summary	Deletes document(s), specified by $path, from the database $db.
Examples	db:delete("DB", "docs/dir/doc.xml") deletes the document docs/dir/doc.xml in the database DB. db:delete("DB", "docs/dir") deletes all documents with paths beginning with docs/dir in the database DB.

db:optimize

Signatures	db:optimize($db as item()) as empty-sequence() db:optimize($db as item(), $all as xs:boolean) as empty-sequence()
Summary	Optimizes the meta data and indexes of the database $db. If $all is set to true(), the complete database will be rebuilt.
Errors	BASX0014 is raised if an error occurs during optimizing the data structures. BASX0015 is raised if the $all flag is set to true(), but the database is an in-memory database. BASX0016 is raised if the database $db is in use by other user(s).
Examples	db:optimize("DB") optimizes the database structures of the database DB. db:optimize("DB", true()) optimizes all database structures of the database DB.

db:rename

Signatures	db:rename($db as item(), $path as xs:string, $newpath as xs:string) as empty-sequence()
Summary	Renames document(s), specified by $path to $newpath in the database $db.
Errors	BXDB0008 is raised if new document names would be empty.
Examples	db:rename("DB", "docs/dir/doc.xml", "docs/dir/newdoc.xml") renames the document docs/dir/doc.xml to docs/dir/newdoc.xml in the database DB. db:rename("DB", "docs/dir", "docs/newdir") renames all documents with paths beginning with docs/dir to paths beginning with docs/newdir in the database DB.

db:replace

Signatures	db:replace($db as item(), $path as xs:string, $input as item()) as empty-sequence()
Summary	Replaces a document, specified by $path, in the database $db with the content of $input.
Errors	BXDB0006 is raised if $path is not a single document path. FODC0002 is raised if $input is a string representing a path, which cannot be read. FOUP0001 is raised if $input is neither a string nor a document node.
Examples	db:replace("DB", "docs/dir/doc.xml", "/home/dir/doc.xml") replaces the content of the document docs/dir/doc.xml in the database DB with the content of the file /home/dir/doc.xml. db:replace("DB", "docs/dir/doc.xml", "<a/>") replaces the content of the document docs/dir/doc.xml in the database DB with <a/>. db:replace("DB", "docs/dir/doc.xml", document { <a/> }) replaces the content of the document docs/dir/doc.xml in the database DB with the specified document node.

db:store

Signatures	db:store($db as item(), $path as xs:string, $data as item()) as empty-sequence()
Summary	Stores a binary resource specified by $data in the database specified by $db and the location specified by $path.
Errors	BXDB0003 is raised if the databse is not persistent (stored on disk). FODC0007 is raised if the specified path is invalid. FOUP0002 is raised if the resource cannot be stored at the specified location.
Examples	db:store("DB", "video/sample.mov", file:read-binary('video.mov')) stores the addressed video file at the specified location.

db:output

Signatures	db:output($data as item()*) as empty-sequence()
Summary	This function can be used to both perform updates and return results in a single query. The argument of the function will be evaluated, and the resulting value will be cached and returned after the updates on the pending update list have been processed. The function can only be used together with updating expressions; if the function is called within a transform expression, its results will be discarded.
Examples	db:output("Prices have been deleted."), delete node //price deletes all price elements in a database and returns an info message.

Helper Functions

db:exists

Signatures	db:exists($db as item()) as xs:boolean db:exists($db as item(), $path as xs:string) as xs:boolean
Summary	Checks if the database specified by $db or the resource specified by {[Mono|$path}} exists. false is returned if a database directory has been addressed.
Examples	db:exists("DB") returns true if the database DB exists. db:exists("DB", "resource") returns true if resource is an XML document or a raw file.

db:is-raw

Signatures	db:is-raw($db as item(), $path as xs:string) as xs:boolean
Summary	Checks if the specified resource in the database $db and the path $path exists, and if it is a raw file.
Examples	db:is-raw("DB", "music/01.mp3") returns true.

db:is-xml

Signatures	db:is-xml($db as item(), $path as xs:string) as xs:boolean
Summary	Checks if the specified resource in the database $db and the path $path exists, and if it is an XML document.
Examples	db:is-xml("DB", "dir/doc.xml") returns true.

db:content-type

Signatures	db:content-type($db as item(), $path as xs:string) as xs:string
Summary	Retrieves the content type of a resource in the database $db and the path $path. The file extension is used to recognize the content-type of a resource stored in the database. Content-type application/xml will be returned for any XML document stored in the database, regardless of its file name extension.
Errors	FODC0002 is raised if the addressed resource is not found or cannot be retrieved.
Examples	db:content-type("DB", "docs/doc01.pdf") returns application/pdf. db:content-type("DB", "docs/doc01.xml") returns application/xml. db:content-type("DB", "docs/doc01") returns application/xml, if db:is-xml("DB", "docs/doc01") returns true.

db:event

Signatures	db:event($name as xs:string, $query as item()) as empty-sequence()
Summary	Executes a $query and sends the resulting value to all clients watching the Event with the specified $name. The query may also perform updates; no event will be sent to the client that fired the event.
Errors	BXDB0010 is raised if the specified event is unknown. SEPM0016 is raised if serialization errors occurred while sending the value.

Errors

Code	Description
BXDB0001	A referenced XML node is no database node, i.e. is neither stored in a database nor a database fragment.
BXDB0002	An I/O error occurred while opening a database.
BXDB0003	The addressed database is not persistent (stored on disk).
BXDB0004	The database lacks an index structure required by the called function.
BXDB0005	A query is expected to exclusively return database nodes of a single database.
BXDB0006	A database path addressed with doc() contains more than one document.
BXDB0007	A database cannot be updated because it is opened by another process.
BXDB0008	Database paths cannot be renamed to empty strings.
BXDB0009	The addressed database id or pre value is out of range.
BXDB0010	The specified event is unknown.

Changelog

Version 7.2.1

• Added: db:text-range, db:attribute-range, db:output

Version 7.1

• Added: db:list-details, db:content-type
• Updated: db:info, db:system, db:retrieve

Version 7.0

• Added: db:retrieve, db:store, db:exists, db:is-raw, db:is-xml
• Updated: db:list, db:open, db:add