Difference between revisions of "Database Module"

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* Updated: [[#db:add|db:add]]: input nodes will be automatically converted to document nodes
 
* Updated: [[#db:add|db:add]]: input nodes will be automatically converted to document nodes
 
* Added: [[#db:backups|db:backups]]
 
* Added: [[#db:backups|db:backups]]
 +
* Added: [[#db:backups|db:create]]
  
 
;Version 7.3
 
;Version 7.3

Revision as of 12:40, 8 November 2012

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.

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: $db references an XML node that is not stored in a database, or is no database fragment.
  • BXDB0002: 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 the database node $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 a string sequence with the names of all databases.
If a database node $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 a database node $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 the database node $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 the database node $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: 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 the database node $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: 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.

db:backups

Introduced with Version 7.5:

Signatures db:backups() as element(backup)*
db:backups($db as item()) as element(backup)*
Summary Returns an element sequence containing all available database backups.
If a database node $db is specified, the sequence will be restricted to the backups matching this database.
Examples
  • db:backups("factbook") returns all backups that have been made from the factbook database.

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 the database node $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, $max as xs:string) as attribute()*
db:attribute-range($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 the database node $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 the database node $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: 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 the nodes supplied by $nodes, which must all be database nodes.
Each database node has a persistent id, which remains valid after update operations. If so far no updates have been performed, the pre value is equal to the id value and can be requested instead, which provides access to database nodes in constant time.
Errors BXDB0001: $nodes contains a node which is not a database node.

db:node-pre

Signatures db:node-pre($nodes as node()*) as xs:integer*
Summary Returns the pre values of the nodes supplied by $nodes, which must all be database 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.
Errors BXDB0001: $nodes contains a node which is not a database node.
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 the database node $db and $path.
Errors BXDB0003: the databse is not persistent (stored on disk).
FODC0002: the addressed resource cannot be retrieved.
FODC0007: 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 the database node $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 the database node $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

Important note: All functions in this section are updating functions: they will not be immediately executed, but queued on the Pending Update List, which will be processed after the actual query has been evaluated. This means that the order in which the functions are specified in the query does usually not reflect the order in which the code will be evaluated.

db:create

Introduced with Version 7.5:

Signatures db:create($db as xs:string) as empty-sequence()
db:create($db as xs:string, $input as item()) as empty-sequence()
db:create($db as xs:string, $input as item(), $path as xs:string) as empty-sequence()
Summary Creates a new database with name $db and adds the initial document $input to the specified $path.
$input may be a string or a node different than attribute. If the $input source is not a file or a folder, $path must be specified.
Errors FODC0002: $input points to an unknown resource.
FOUP0001: $input is neither string nor a document node.
FOUP...: ...
Examples
  • db:create("DB", "/home/dir/doc.xml") creates the database DB and adds the file /home/dir/doc.xml as initial content.

db:add

Updated in Version 7.5: Node inputs will be automatically converted to document nodes.

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 specified by the database node $db and the specified $path.
$input may be a string or a node different than attribute.
Errors FODC0002: $input points to an unknown resource.
FOUP0001: $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", <a/>, "doc.xml") adds a 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 specified by the database node $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 specified by the database node $db.
If $all is set to true(), the complete database will be rebuilt.
Errors FOUP0002: an error occurred while optimizing the database.
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 specified by the database node $db.
Errors BXDB0008: 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

Updated in Version 7.5: Node inputs will be automatically converted to document nodes.

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 specified by the database node $db with the content of $input, or adds it as a new document.
Errors BXDB0006: $path is not a single document path.
FODC0002: $input is a string representing a path, which cannot be read.
FOUP0001: $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, $input as item()) as empty-sequence()
Summary Stores a binary resource specified by $input in the database specified by the database node $db and the location specified by $path.
Errors BXDB0003: the databse is not persistent (stored on disk).
FODC0007: the specified path is invalid.
FOUP0002: 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.

db:flush

Introduced with Version 7.3:

Signatures db:flush($db as item()) as empty-sequence()
Summary Explicitly flushes the buffers of the database specified by the database node $db. This command is only useful if AUTOFLUSH has been set to false.

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 the database node $db or the resource specified by {[Mono|$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 specified by the database node $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 specified by the database node $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 specified by the database node $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: 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: the specified event is unknown.
SEPM0016: 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.
BXDB0011 The name of the specified database is invalid.
BXDB0012 A database can only be created once.

Changelog

Version 7.5
Version 7.3
Version 7.2.1
Version 7.1
Version 7.0