Difference between revisions of "Database Module"

From BaseX Documentation
Jump to navigation Jump to search
Line 37: Line 37:
 
|-
 
|-
 
| valign='top' | '''Summary'''
 
| valign='top' | '''Summary'''
|Returns an {{Mono|element}} sequence with the names of all databases together with their database path, the number of stored resources and the date of modification.
+
|Returns an {{Mono|element}} sequence with the names of all databases together with their database path, the number of stored resources and the date of modification.<br/>If {{Mono|$db}} is specified, all documents and raw files of the specified database are returned.<br/>The list of resources can be further restricted by the {{Mono|$path}} argument.
 
|}
 
|}
  

Revision as of 12:09, 7 February 2012

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.

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: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 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()