Difference between revisions of "Database Module"
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− | |Returns a binary database resource addressed by the [[#Database Nodes|database node]] {{Code|$db}} and {{Code|$path}}. | + | |Returns a binary database resource addressed by the [[#Database Nodes|database node]] {{Code|$db}} and {{Code|$path}} as streamable {{Code|xs:base64Binary}}. |
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* {{Code|declare option output:method 'raw';<br/>db:retrieve("DB", "music/01.mp3")}} returns the specified audio file as raw data. | * {{Code|declare option output:method 'raw';<br/>db:retrieve("DB", "music/01.mp3")}} returns the specified audio file as raw data. | ||
+ | * <code><nowiki>data(db:retrieve("DB", "music/01.mp3"))</nowiki></code> returns a materialized representation of the streamable result. | ||
|} | |} | ||
Revision as of 20:59, 28 January 2013
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.
Contents
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 $path argument.
|
Examples |
|
db:list-details
Signatures | db:list-details() as element(database)* db:list-details($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 $path argument.
|
Examples |
|
db:open
Signatures | db:open($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 $path argument.
|
Examples |
|
db:open-id
Signatures | db:open-id($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 $pre value.The pre value provides access to a database node in constant time, but it is transient, i.e., it may change when database updates are performed. |
Errors | BXDB0009 : the specified pre value does not exist in the database.
|
Examples |
|
db:system
Signatures | db:system() as element(system)
|
Summary | Returns information on the database system, such as the database path and current database settings. |
db:backups
Signatures | db:backups() as element(backup)* db:backups($db as item()) as element(backup)*
|
Summary | Returns an element sequence containing all available database backups. If a database node $db is specified, the sequence will be restricted to the backups matching this database.
|
Examples |
|
Read Operations
db:attribute
Signatures | db:attribute($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 $attname is specified, the resulting attribute nodes are filtered by their attribute name.
|
Examples |
|
db:attribute-range
Signatures | db:attribute-range($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 $max . If available, the value index is used to speed up evaluation.
|
Examples |
|
db:fulltext
Signatures | db:fulltext($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 $terms .The options used for building the full-text will also be applied to the search terms. As an example, if the index terms have been stemmed, the search string will be stemmed as well. |
Errors | BXDB0004 : the full-text index is not available.
|
Examples |
|
db:node-id
Signatures | db:node-id($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 : $nodes contains a node which is not a database node.
|
Examples |
|
db:retrieve
Signatures | db:retrieve($db as item(), $path as xs:string) as xs:base64Binary
|
Summary | Returns a binary database resource addressed by the database node $db and $path as streamable xs:base64Binary .
|
Errors | BXDB0003 : the databse is not persistent (stored on disk).FODC0002 : the addressed resource cannot be retrieved.FODC0007 : the specified path is invalid.
|
Examples |
|
db:text
Signatures | db:text($db as item(), $string as item()) as text()*
|
Summary | Returns all text nodes of the database specified by the database node $db that have $string as their string value. If available, the value index is used to speed up evaluation.
|
Examples |
|
db:text-range
Signatures | db:text-range($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 $max strings. If available, the value index is used to speed up evaluation.
|
Examples |
|
Updates
Important note: All functions in this section are updating functions: they will not be immediately executed, but queued on the Pending Update List, which will be processed after the actual query has been evaluated. This means that the order in which the functions are specified in the query does usually not reflect the order in which the code will be evaluated.
db:create
Signatures | db:create($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.Please note that db:create will be placed last on the Pending Update List. As a consequence, a newly created database cannot be addressed in the same query.
|
Errors | FODC0002 : $input points to an unknown resource.FOUP0001 : $input is neither string nor a document node.BXDB0007 : $db is opened by another process.BXDB0011 : $db is not a valid database name.BXDB0012 : two db:create statements with the same database name were specified.
|
Examples |
|
db:drop
Signatures | db:drop($db as item()) as empty-sequence()
|
Summary | Drops the database specified by the database node $db and all connected resources.
|
Errors | BXDB0007 : $db is opened by another process.
|
Examples |
|
db:add
Template:Mark Node inputs will be automatically converted to document nodes.
Signatures | db:add($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. If the $input source is not a file or a folder, $path must be specified.
|
Errors | FODC0002 : $input points to an unknown resource.FOUP0001 : $input is neither string nor a document node.
|
Examples |
|
db:delete
Signatures | db:delete($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 $db .
|
Examples |
|
db:optimize
Signatures | db:optimize($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 $all is set to true() , the complete database will be rebuilt.
|
Errors | FOUP0002 : an error occurred while optimizing the database.
|
Examples |
|
db:rename
Signatures | db:rename($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 $db .
|
Errors | BXDB0008 : new document names would be empty.
|
Examples |
|
db:replace
Template:Mark Node inputs will be automatically converted to document nodes.
Signatures | db:replace($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 : $input is neither a string nor a document node.
|
Examples |
|
db:store
Signatures | db:store($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 $path .
|
Errors | BXDB0003 : the databse is not persistent (stored on disk).FODC0007 : the specified path is invalid.FOUP0002 : the resource cannot be stored at the specified location.
|
Examples |
|
db:output
Signatures | db:output($result 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 items will be cached and returned after the updates on the pending update list have been processed. As nodes may be updated, they will be copied before being cached. 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:flush
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 $path exists. false is returned if a database directory has been addressed.
|
Examples |
|
db:is-raw
Signatures | db:is-raw($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 $path exists, and if it is a raw file.
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Examples |
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db:is-xml
Signatures | db:is-xml($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 $path exists, and if it is an XML document.
|
Examples |
|
db:content-type
Signatures | db:content-type($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 $path .The file extension is used to recognize the content-type of a resource stored in the database. Content-type application/xml will be returned for any XML document stored in the database, regardless of its file name extension.
|
Errors | FODC0002 : the addressed resource is not found or cannot be retrieved.
|
Examples |
|
db:event
Signatures | db:event($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
- Updated: db:add: input nodes will be automatically converted to document nodes
- Added: db:backups
- Added: db:create
- Added: db:drop
- Version 7.3
- Added: db:flush
- 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