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Multiple databases can be addressed (queries, updated) with a single XQuery expression. As a single database is restricted to 2 billion XML nodes (see [[Statistics]]), but resources can easily be distributed across multiple database instances.Multiple databases can be addressed (queried, updated) by a single XQuery expression. Three different resource types exist: {|class="wikitable"|- valign="top"| '''Resource Type'''| '''Description'''|- valign="top"| XML Documents| The default resource type. The storage and index features are optimized for XML contents, or any other contents stored in an XML representation.|- valign="top"| Binary Data| Binary data: Raw data of any type, stored in its binary representation. See [[Binary Data]] for more information.|- valign="top"| XQuery Values| Results of XQuery expressions, stored in a binary representation for fast retrieval. All value types are supported, including maps and arrays, but excluding any other [[Higher-Order Functions#Function Items|function items]].|}
The name of a database is restricted to a restricted set of characters (see * [[Valid NamesStartup#BaseX Standalone|Command-Line]]): <code>CREATE DB documents /path/to/resources</code>: Add resources in the specified path to a database named {{Code|documents}}. Various * [[parsersStartup#BaseX GUI|GUI]] can be chosen : Go to control the import process''Database'' → ''New'', press ''Browse…'' to choose an initial file or to convert different formats to XMLdirectory, and press ''OK''.
'''Note:''' A main-memory The database will be created if the {{Option|MAINMEM}} option name is enabled composed of a restricted set of characters (see [[Databases#In Memory Database|see belowValid Names]] for more). Various [[Parsers]] can be selected to control the import process, or to convert data of different input type to XML.
The <code>[[Commands#RETRIEVE|RETRIEVE]]</code> command and If the API you use does not support binary output (which is e.g. the <code>case for various [[Database Module#db:retrieveClients|db:retrieveClient]]</code> function language bindings), you can be used convert your binary data to return files in their native byte its string representation.before returning it to the client:
If the API you use does not support <pre lang='xquery'>string(db:get-binary output (this is e'multimedia', 'sample.g. the case for various [[Clients|Client]] language bindingsavi')), you need to convert your binary data to its string representation before returning it to the client:</pre>
<syntaxhighlight lang="xquery">string(db:retrieve('multimedia', 'sample.avi'))</syntaxhighlight>=XQuery Values==
==HTTP Services==With {{Function|Database|db:get-value}}, XQuery values can be retrieved. In the following example, we assume that an XQuery map {{Code|cities}} was stored in an {{Code|indexes}} database:
* With [[REST]] and [[WebDAV]], all database resources can be requested in a uniform way<pre lang='xquery'>let $city-map := db:get-value('indexes', no matter if they are well'cities')return $city-formed XML documents or binary files.map?Chile</pre>
The {{Option|AUTOFLUSH}} option can be turned off before ''bulk operations'' (i.e. , before a large number of numerous new resources is are added to the database).
The With the following commands create [[Commands#Command Scripts|command script]], an empty databaseis created, add two resourcesare added (one directly, explicitly flush data structures to diskanother one cached), and finally delete all inserted datais exported to the file system:
STORE BINARY PUT TO images/ 123.jpgFLUSHEXPORT /path/to/file-system/</pre> ==XQuery== DELETE You can also use functions from the [[Database Module]] to add, replace, or delete XML documents: <pre lang='xquery'>db:add('documents', '/path/to/xml/resources/')</syntaxhighlightpre>
You may also use Function from other modules, such as the BaseX-specific [[Database File Module|XQuery Database Functions]] , can be utilized to createfilter the input. With the following code, addall files that contain numbers in the filename are selected, replaceand stored as XML. If an input file contains no well-formed XML, it is stored as binary resource, and delete XML documentsthe error message is stored as a string value:
Last but not least, XML documents The error messages can also e.g. be added via the GUI and the ''Database'' menu.analyzed in a second step:
All resources stored in a database can be ''exported'', i.e., written back to disk. This can be done in several ways:=Export Database=
* Commands: <code>[[Commands#EXPORT|EXPORT]]</code> writes all All resources to the specified target directory* GUI: Go to stored in a database can be ''Database'' → ''Exportexported'', choose the target directory and press ''OK''* WebDAVi.e., written back to disk, e.g., as follows: Locate the database directory (or a sub-directory of it) and copy all contents to another location
=Main-Memory * Commands: {{Command|EXPORT}} writes all resources to the specified target directory.* GUI: Go to ''Database Instances='' → ''Export'', choose the target directory and press ''OK''.* XQuery: Use {{Function|Database|db:export}}.* WebDAV: Locate the database directory (or a subdirectory of it) and copy all contents to another location.
* In the standalone context, a main=Main-memory database can be created (using <code>CREATE DB</code>), which can then be accessed by subsequent commands.* If a BaseX server instance is started, and if a database is created in its context (using <code>CREATE DB</code>), other BaseX client instances can access (and update) this database (using OPEN, db:open, etc.) as long as no other database is opened/created by the server.* You can force an ordinary database to being copied to memory by using <code>db:open('some-db') update {}</code>Memory Databases=
Text replacement - "syntaxhighlight" to "pre"
This page is part of the [[Getting Started]] Section.
In BaseX, a ''database'' is a pretty light-weight concept. It may contain one or more '''resources''', which are addressed by a unique database path. There is no explicit layer for collections: Instead, collections are implicitly created and deleted, and collections result from the existence of documents in specific paths. Resources can either be '''XML documents''' or '''raw files''' (binaries). Some information on [[Binary Data|binary data]] can be found on an extra page.
=Create Databases=
Databases can be created via commands[[Commands]], via [[XQuery]], in the [[GUI]], or and with any of our various [[Developing|APIs]]. If an initial input is specified with a createoperation, some time can be saved, as the specified resources will be added to the database in a bulk operation: * [[Startup#BaseX Standalone|Console]]: <code>CREATE DB db /path/to/resources</code> will add initial documents to a database* [[Startup#BaseX GUI|GUI]]: Go to ''Database'' → ''New'', press ''Browse'' to choose an initial file or directory, and press ''OK''
=Access Resources=
{| class="wikitable"
|-valign="top"
!Function
!Example
!Description
|-valign="top"|[[{{Function|Database Module#db:open|db:open]]get}}|{{Code|db:openget("db", "path/to/docs")}}
|Returns all documents that are found in the database {{Code|db}} at the (optional) path {{Code|path/to/docs}}.
|-valign="top"|<code>[http://www.xqueryfunctions.com/xq/fn_collection.html fn:collection]</code>
|{{Code|collection("db/path/to/docs")}}
|Returns all documents at the location {{Code|path/to/docs}} in the database {{Code|db}}.<br/>If no path is specified after the database, all documents in the database will be returned.<br/>If no argument is specified, all documents of the database will be returned that has been opened in the global context.
|-valign="top"|<code>[http://www.xqueryfunctions.com/xq/fn_doc.html fn:doc]</code>
|{{Code|doc("db/path/to/doc.xml")}}
|Returns the document at the location {{Code|path/to/docs}} in the database {{Code|db}}.<br/>An error is raised if the specified yields zero or more than one document.
You can access multiple databases in a single query:
<syntaxhighlight pre lang="'xquery"'>
for $i in 1 to 100
return db:openget('books' || $i)//book/title</syntaxhighlightpre>
If the {{Option|DEFAULTDB}} option is turned on, the path argument of the {{Code|fn:doc}} or {{Code|fn:collection}} function functions will first be resolved against the globally opened database.
Two more functions are available for retrieving information on database nodes:
!Example
!Description
|-valign="top"|[[{{Function|Database Module#db:name|db:name]]}}
|{{Code|db:name($node)}}
|Returns the name of the database in which the specified {{Code|$node}} is stored.
|-valign="top"|[[{{Function|Database Module#db:path|db:path]]}}
|{{Code|db:path($node)}}
|Returns the path of the database document in which the specified {{Code|$node}} is stored.
The {{Code|fn:document-uri}} and {{Code|fn:base-uri}} functions return URIs that can also be reused as arguments for the {{Code|fn:doc}} and {{Code|fn:collection}} functions. As a result, the following example query always returns {{Code|true}}:
<syntaxhighlight pre lang="'xquery"'>
every $c in collection('anyDB')
satisfies doc-available(document-uri($c))
</syntaxhighlightpre>
If the argument of {{Code|fn:doc}} or {{Code|fn:collection}} does not start with a valid database name, or if the addressed database does not exist, the string is interpreted as URI reference, and the documents found at this location will be returned. Examples:
* {{Code|collection("/path/to/docs")}}: returns a main-memory collection with all XML documents found at the addressed file path.
==Raw FilesBinary Data== The {{Command|BINARY GET}} command and the {{Function|Database|db:get-binary}} function can be used to return files in their native byte representation.
=Update Resources=
==Commands==
Once you have created a database, additional commands exist to modify its contents:
* XML documents can be added with the <code>[[Commands#ADD{{Command|PUT}} and {{Command|ADD]]</code> command.* Raw files are added with <code>[[Commands#STORE|STORE]]</code>}} commands.* Existing resources can be replaced Binary data is stored with the <code>[[Commands#REPLACE{{Command|REPLACE]]</code> commandBINARY PUT}}.* Resources of all types can be deleted via <code>[[Commands#DELETE{{Command|DELETE]]</code>}}.
If {{Option|ADDCACHE}} is enabled, the input will be cached before it is added to the database. This is helpful when the input documents to be added are expected to consume too much main -memory.
<syntaxhighlightpre>
CREATE DB example
SET AUTOFLUSH false
SET ADDCACHE true
ADD /path/to/xml/documents
<syntaxhighlight pre lang="'xquery"'>let $db := 'documents'let $root := "'/path/to/xml/documentsresources/"'for $file path in file:list($root)where matches($path, '\d+')return try { db:addput("database"$db, fetch:doc($root || $filepath), $path)} catch * { db:put-binary($db, $root || $path, $path), db:put-value($db, $err:description, $path || '.error')}</syntaxhighlightpre>
<pre lang=Export Data'xquery'>let $errors :=db:get-value('documents')for $filename in map:keys($errors)where ends-with($filename, '.error')return $filename || ': ' || $errors?($filename)</pre>
A database can be created in main-memory by enabling the {{Option|MAINMEM}} option. Next, in the standalone context, a main-memory database can be created, which can then be accessed by subsequent commands. If a BaseX server is started, and if a database is created in its context at startup time, e.g., with the [[Command-Line Options|command-line option -c]] and a {{Command|CREATE DB}} call, BaseX clients can then access and update this database: <pre lang="perl"># Serverbasexserver -c"SET mainmem on" -c"CREATE DB mainmem document.xml"BaseX [Server]Server was started (port: 1984).MAINMEM: trueDatabase 'mainmem' created in 1782.80 ms. # ClientbasexclientUsername: ...Password: ...BaseX [Client]Try 'help'Noteto get more information.> XQUERY count(db:get('mainmem')//*)1876462Query executed in 0.97 ms.</pre> Additional notes:* You can force an ordinary database, or parts of it, to being temporarily copied to memory by applying an empty [[XQuery_Update#Main-Memory_Updates|main-memory update]] on a database node: <code>db:get('some-db' ) update { }</code>* If you address a URI open local or remote documents with <code>fn:doc</code> or <code>fn:collection</code> for which no database exists, the resulting internal representation is identical to those of main-memory database instances (no matter regardless of which value is set for {{Option|MAINMEM}}).
=Changelog=
;Version 10.0
* Added: New resource type for XQuery values.
;Version 8.4
* Updated: [[#Raw Files|Raw Files]]: Items of binary type can be output without specifying the obsolete <code>raw</code> serialization method.
;Version 7.2.1
* Updated: {{Code|fn:document-uri}} and {{Code|fn:base-uri}} now return strings that can be reused with {{Code|fn:doc}} or {{Code|fn:collection}} to reopen the original document.
