Database Module

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

This preview page contains all commands offered by the latest stable snapshot. There is also another page, which lists the functions of the current release.

Commonalities

Many functions share $db as argument, which may either reference a string, denoting the name of the addressed database, or a node from an already opened database. The following errors may be raised by these functions:

• BASX0002 is raised if $db references a node that is not stored in a database (i.e., references a main-memory XML fragment).
• BASX0003 is raised if the addressed database cannot be opened.

General Functions

db:info

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

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.

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.

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	BASX0004 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 that have $string as their string value. 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:fulltext

Signatures	db:fulltext($db as item(), $text as item()) as text()*
Summary	Returns all text nodes from the full-text index that contain the string $text. The index full-text options will be applied here: if the index terms have been stemmed, the search string will be stemmed as well.
Errors	BASX0001 is raised if the 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 database nodes specified by $nodes. 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 database nodes specified by $nodes. 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	FODC0002 is raised if the addressed resource is not found or cannot be retrieved.
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 that have $string as their string value.
Examples	db:text("DB", "QUERY")/.. returns the parents of all text nodes of the database DB that match the string QUERY.

Updates

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 not a string and not 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", "<a/>") 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	BASX0013 is raised if new document name(s) will 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	BASX0012 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 not a string and not 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 at the location specified by $path.
Errors	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.

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 specified database or resource exists. false is returned if a database directory is specified.
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 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 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 the resource specified by $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	BASX0009 is raised if the specified event is unknown. SEPM0016 is raised if serialization errors occurred while sending the value.

Recent Changes

Version 7.1

• Added: db:list-details(), db:content-type()
• Modified: db:info(), db:system(), db:retrieve()

Version 7.0

• Added: db:retrieve(), db:store(), db:exists(), db:is-raw(), db:is-xml()
• Modified: db:list(), db:open(), db:add()