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.
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
Database nodes are XML nodes which are either stored in a persistent database or part of a so-called database fragment. All XML fragments can be converted to database fragments by e. g. applying the transform expression on an XML fragment:
copy $c := element hello { 'world' } modify () return $c
General Functions
db:system
Signatures | db:system() as element(system)
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Summary | Returns information on the database system, such as the database path and current database settings. The output is similar to the INFO command. |
db:info
Signatures | db:info($db as xs:string) as element(database)
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Summary | Returns meta information on the database $db . The output is similar to the INFO DB command.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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db:list
Signatures | db:list() as xs:string* db:list($db as xs:string) as xs:string* db:list($db as xs:string, $path as xs:string) as xs:string*
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Summary | Returns a string sequence with the names of all databases:
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:list-details
Signatures | db:list-details() as element(database)* db:list-details($db as xs:string) as element(resource)* db:list-details($db as xs:string, $path as xs:string) as element(resource)*
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Summary | Returns an element sequence with the names of all databases together with their database path, the number of stored resources and the date of modification:
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:backups
Signatures | db:backups() as element(backup)* db:backups($db as xs:string) as element(backup)*
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Summary | Returns an element sequence containing all available database backups. If a database $db is specified, the sequence will be restricted to the backups matching this database.
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Examples |
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db:event
Signatures | db:event($name as xs:string, $query as item()) as empty-sequence()
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Summary | Executes a $query and sends the resulting value to all clients watching the Event with the specified $name . The query may also perform updates; no event will be sent to the client that fired the event.
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Errors | BXDB0010 : the specified event is unknown.SEPM0016 : serialization errors occurred while sending the value. |
Read Operations
db:open
Signatures | db:open($db as xs:string) as document-node()* db:open($db as xs:string, $path as xs:string) as document-node()*
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Summary | Returns a sequence with all document nodes contained in the database $db .The document nodes to be returned can be restricted by the $path argument.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:open-pre
Signatures | db:open-pre($db as xs:string, $pre as xs:integer) as node()
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Summary | Opens the database $db and returns the node with the specified $pre value.The PRE value provides very fast access to an existing database node, but it will change whenever a node with a smaller pre values is added to or deleted from a database. |
Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0009 : the specified pre value does not exist in the database.
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Examples |
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db:open-id
Signatures | db:open-id($db as xs:string, $id as xs:integer) as node()
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Summary | Opens the database $db and returns the node with the specified $id value.Each database node has a persistent ID value. Access to the node id can be sped up by turning on the UPDINDEX option. |
Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0009 : the specified id value does not exist in the database.
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db:node-pre
Signatures | db:node-pre($nodes as node()*) as xs:integer*
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Summary | Returns the pre values of the nodes supplied by $nodes , which must all be database nodes.The PRE value provides very fast access to an existing database node, but it will change whenever a node with a smaller pre values is added to or deleted from a database. |
Errors | BXDB0001 : $nodes contains a node which is not stored in a database.
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Examples |
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db:node-id
Signatures | db:node-id($nodes as node()*) as xs:integer*
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Summary | Returns the id values of the nodes supplied by $nodes , which must all be database nodes.Each database node has a persistent ID value. Access to the node id can be sped up by turning on the UPDINDEX option. |
Errors | BXDB0001 : $nodes contains a node which is not stored in a database.
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db:retrieve
Signatures | db:retrieve($db as xs:string, $path as xs:string) as xs:base64Binary
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Summary | Returns a binary resource addressed by the database $db and $path as streamable xs:base64Binary .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0003 : the database is not persistent (stored on disk).FODC0002 : the addressed resource cannot be retrieved.FODC0007 : the specified path is invalid.
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Examples |
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db:export
Signatures | db:export($db as xs:string, $path as xs:string) as empty-sequence() db:export($db as xs:string, $path as xs:string, $params as item()) as empty-sequence() |
Summary | Exports the specified database $db to the specified file $path . Existing files will be overwritten. The $params argument contains serialization parameters (see Serialization for more details), which can either be specified
<output:serialization-parameters> <output:method value='xml'/> <output:cdata-section-elements value="div"/> ... </output:serialization-parameters>
map { "method" := "xml", "cdata-section-elements" := "div", ... } |
Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Contents
db:text
Signatures | db:text($db as xs:string, $string as item()) as text()*
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Summary | Returns all text nodes of the database $db that have $string as their string value. If available, the value index is used to speed up evaluation.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:text-range
Signatures | db:text-range($db as xs:string, $min as xs:string, $max as xs:string) as text()*
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Summary | Returns all text nodes of the database $db that are located in between the $min and $max strings. If available, the value index is used to speed up evaluation.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:attribute
Signatures | db:attribute($db as xs:string, $string as item()) as attribute()* db:attribute($db as xs:string, $string as item(), $attname as xs:string) as attribute()*
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Summary | Returns all attribute nodes of the database $db that have $string as string value. If available, the value index is used to speed up evaluation.If $attname is specified, the resulting attribute nodes are filtered by their attribute name.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:attribute-range
Signatures | db:attribute-range($db as xs:string, $min as xs:string, $max as xs:string) as attribute()* db:attribute-range($db as xs:string, $min as xs:string, $max as xs:string, $attname as xs:string) as attribute()*
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Summary | Returns all attributes of the database $db , the string values of which are larger than or equal to $min and smaller than or equal to $max . If available, the value index is used to speed up evaluation.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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Updates
Important note: All functions in this section are updating functions: they will not be immediately executed, but queued on the Pending Update List, which will be processed after the actual query has been evaluated. This means that the order in which the functions are specified in the query does usually not reflect the order in which the code will be evaluated.
db:create
Signatures | db:create($db as xs:string) as empty-sequence() db:create($db as xs:string, $inputs as item()*) as empty-sequence() db:create($db as xs:string, $inputs as item()*, $paths as xs:string*) as empty-sequence() db:create($db as xs:string, $inputs as item()*, $paths as xs:string*, $options as item()) as empty-sequence()
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Summary | Creates a new database with name $db and adds initial documents specified via $inputs to the specified $paths . An existing database will be overwritten.$inputs may be strings or nodes different than attributes. If the $input source is not a file or a folder, the $paths argument is mandatory.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.The
<options> <textindex value='true'/> <maxcats value='128'/> </options>
map { "textindex" := true(), "maxcats" = 128 } |
Errors | FODC0002 : $inputs points to an unknown resource.FOUP0001 : $inputs is neither string nor a document node.BXDB0007 : $db is opened by another process.BXDB0011 : $db is not a valid database name.BXDB0012 : two db:create statements with the same database name were specified.BXDB0013 : the number of specified inputs and paths differs.
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Examples |
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db:drop
Signatures | db:drop($db as xs:string) as empty-sequence()
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Summary | Drops the database $db and all connected resources.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0007 : $db is opened by another process.
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Examples |
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db:add
Signatures | db:add($db as xs:string, $input as item()) as empty-sequence() db:add($db as xs:string, $input as item(), $path as xs:string) as empty-sequence()
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Summary | Adds documents specified by $input to the database $db and the specified $path . A document with the same path may occur than once in a database. If this is unwanted, db:replace can be used.$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.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.FODC0002 : $input points to an unknown resource.FOUP0001 : $input is neither string nor a document node.
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Examples |
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db:delete
Signatures | db:delete($db as xs:string, $path as xs:string) as empty-sequence()
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Summary | Deletes document(s), specified by $path , from the database $db .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:create-backup
Signatures | db:create-backup($db as xs:string) as empty-sequence()
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Summary | Creates a backup of the database $db .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0011 : Invalid database name.
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Examples |
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db:optimize
Signatures | db:optimize($db as xs:string) as empty-sequence() db:optimize($db as xs:string, $all as xs:boolean) as empty-sequence() db:optimize($db as xs:string, $all as xs:boolean, $options as item()) as empty-sequence()
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Summary | Optimizes the meta data and indexes of the database $db .If $all is set to true() , the complete database will be rebuilt.The usage of the $options argument is identical to the db:create function, except that the UPDINDEX option is not supported.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.FOUP0002 : an error occurred while optimizing the database.
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Examples |
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db:rename
Signatures | db:rename($db as xs:string, $path as xs:string, $newpath as xs:string) as empty-sequence()
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Summary | Renames document(s), specified by $path to $newpath in the database $db .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0008 : new document names would be empty.
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Examples |
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db:replace
Signatures | db:replace($db as xs:string, $path as xs:string, $input as item()) as empty-sequence()
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Summary | Replaces a document, specified by $path , in the database $db with the content of $input , or adds it as a new document.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0014 : $path points to a directory.FODC0002 : $input is a string representing a path, which cannot be read.FOUP0001 : $input is neither a string nor a document node.
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Examples |
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db:store
Signatures | db:store($db as xs:string, $path as xs:string, $input as item()) as empty-sequence()
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Summary | Stores a binary resource specified by $input in the database $db and the location specified by $path .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.BXDB0003 : the database is not persistent (stored on disk).FODC0007 : the specified path is invalid.FOUP0002 : the resource cannot be stored at the specified location.
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Examples |
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db:output
Signatures | db:output($result as item()*) as empty-sequence()
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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 |
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db:flush
Signatures | db:flush($db as xs:string) as empty-sequence()
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Summary | Explicitly flushes the buffers of the database $db . This command is only useful if AUTOFLUSH has been set to false .
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Helper Functions
db:name
Signatures | db:name($node as node()) as xs:string
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Summary | Returns the name of the database in which the specified database node $node is stored.
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Errors | BXDB0001 : $nodes contains a node which is not stored in a database.
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db:path
Signatures | db:path($node as node()) as xs:string
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Summary | Returns the path of the database document in which the specified database node $node is stored.
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Errors | BXDB0001 : $nodes contains a node which is not stored in a database.
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db:exists
Signatures | db:exists($db as xs:string) as xs:boolean db:exists($db as xs:string, $path as xs:string) as xs:boolean
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Summary | Checks if the database $db or the resource specified by $path exists. false is returned if a database directory has been addressed.
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Examples |
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db:is-raw
Signatures | db:is-raw($db as xs:string, $path as xs:string) as xs:boolean
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Summary | Checks if the specified resource in the database $db and the path $path exists, and if it is a binary resource.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Examples |
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db:is-xml
Signatures | db:is-xml($db as xs:string, $path as xs:string) as xs:boolean
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.
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Summary | Checks if the specified resource in the database $db and the path $path exists, and if it is an XML document.
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Examples |
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db:content-type
Signatures | db:content-type($db as xs:string, $path as xs:string) as xs:string
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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.
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Errors | BXDB0002 : The addressed database does not exist or could not be opened.FODC0002 : the addressed resource is not found or cannot be retrieved.
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Examples |
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Errors
Code | Description |
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BXDB0001
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The referenced XML node is no database node, i.e. it is neither stored in a database nor represented as database fragment. |
BXDB0002
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The addressed database does not exist or could not be opened. |
BXDB0003
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The addressed database is not persistent (stored on disk). |
BXDB0004
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The database lacks an index structure required by the called function. |
BXDB0005
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A query is expected to exclusively return database nodes of a single database. |
BXDB0006
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A database path addressed with doc() contains more than one document.
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BXDB0007
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A database cannot be updated because it is opened by another process. |
BXDB0008
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Database paths cannot be renamed to empty strings. |
BXDB0009
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The addressed database id or pre value is out of range. |
BXDB0010
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The specified event is unknown. |
BXDB0011
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The name of the specified database is invalid. |
BXDB0012
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A database can only be created once. |
BXDB0013
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The number of specified inputs and paths differs. |
BXDB0014
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Path points to a directory. |
Changelog
- Version 7.8
- Removed: db:fulltext (use ft:search instead)
- Version 7.7
- Added: db:export, db:name, db:path
- Updated:
$options
argument added to db:create and db:optimize. - Updated: the functions no longer accept Database Nodes as reference. Instead, the name of a database must now be specified.
- Version 7.6
- Updated: db:create: allow more than one input and path.
- 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