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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]].|}
* 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 [[Options#AUTOFLUSH{{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 [[Options#ADDCACHEIf {{Option|ADDCACHE]] option will first cache }} is enabled, the input will be cached before adding it is added to the database. This is helpful when the input documents to be added are expected to eat up consume too much main -memory.
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.jpgFLUSHDELETE EXPORT /path/to/file-system/
Last but not leastFunction from other modules, such as the [[File Module]], XML documents can also be added via utilized to filter the input. With the following code, all files that contain numbers in the GUI filename are selected, and stored as XML. If an input file contains no well-formed XML, it is stored as binary resource, and the error message is stored as a string value: <pre lang='xquery'>let $db := 'documents'let $root := '/path/to/resources/'Databasefor $path in file:list($root)where matches($path, '\d+')return try { db:put($db, fetch:doc($root || $path), $path)} catch * { db:put-binary($db, $root || $path, $path), db:put-value($db, $err:description, $path || ' menu.error')}</pre>
=Export Data=The error messages can e.g. be analyzed in a second step:
All resources stored in a database can be <pre lang='xquery'exported>let $errors := db:get-value('documents')for $filename in map:keys($errors)where ends-with($filename, i'.e., written back to disk. This can be done in several wayserror')return $filename || ':' || $errors?($filename)</pre>
* Commands: <code>[[Commands#EXPORT|EXPORT]]</code> writes all resources to the specified target directory* GUI: Go to ''=Export Database'' → ''Export'', choose the target directory and press ''OK''* WebDAV: Locate the database directory (or a sub-directory of it) and copy all contents to another location=
=Main-Memory Database Instances=All resources stored in a database can be ''exported'', i.e., written back to disk, e.g., as follows:
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|ConsoleCommand-Line]]: <code>CREATE DB db documents /path/to/resources</code> will add initial documents : Add resources in the specified path to a databasenamed {{Code|documents}}.* [[Startup#BaseX GUI|GUI]]: Go to ''Database'' → ''New'', press ''BrowseBrowse…'' to choose an initial file or directory, and press ''OK''.
The database name is composed of a database is restricted to a restricted set of characters (see [[Valid Names]]). Various [[parsersParsers]] can be chosen selected to control the import process, or to convert data of different formats input type to XML. '''Note:''' A main-memory database will be created if the {{Option|MAINMEM}} option is enabled ([[Databases#In Memory Database|see below]] for more).
=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:
<pre classlang="brush:'xquery"'>
for $i in 1 to 100
return db:openget('books' || $i)//book/title
</pre>
If the [[Options#DEFAULTDB{{Option|DEFAULTDB]] }} option is turned on, the path argument of the {{Code|fn:doc}} or {{Code|fn:collection}} function functions will first be resolved against the globally opened database.
Two more functions are available for retrieving information on database nodes:
!Example
!Description
|-valign="top"|[[{{Function|Database Module#db:name|db:name]]}}
|{{Code|db:name($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}}:
<pre classlang="brush:'xquery"'>
every $c in collection('anyDB')
satisfies doc-available(document-uri($c))
* {{Code|doc("http://web.de")}}: retrieves the addressed URI and returns it as a main-memory document node.
* {{Code|doc("myfile.xml")}}: retrieves the given file from the file system and returns it as a main-memory document node. Note that updates to main-memory nodes are not automatically written back to disk unless the <code>[[Options#WRITEBACK{{Option|WRITEBACK]]</code> }} option is set.
* {{Code|collection("/path/to/docs")}}: returns a main-memory collection with all XML documents found at the addressed file path.
==Raw FilesBinary Data==
The <code>[[Commands#RETRIEVE{{Command|RETRIEVE]]</code> BINARY GET}} command and the <code>[[{{Function|Database Module#db:retrieve|db:retrieve]]</code> get-binary}} function can be used to return files in their native byte representation.
If the API you use does not support binary output (this which is e.g. the case for various [[Clients|Client]] language bindings), you need to can convert your binary data to its string representation before returning it to the client:
<pre classlang="brush:'xquery"'>string(db:retrieveget-binary('multimedia', 'sample.avi'))
</pre>
==HTTP ServicesXQuery Values== 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:
=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>}}.
<pre>
SET ADDCACHE true
ADD /path/to/xml/documents
</pre>
==XQuery== You may can also use functions from the BaseX-specific [[Database Module|XQuery Database Functions]] to create, add, replace, and or delete XML documents:
<pre classlang="brush:'xquery"'>let $root db:= "add('documents', '/path/to/xml/documentsresources/"for $file in file:list($root)return db:add("database", $root || $file')
</pre>
* In Commands: {{Command|EXPORT}} writes all resources to the standalone context, a main-memory database can be created (using <code>CREATE DB</code>), which can then be accessed by subsequent commandsspecified target directory.* If a BaseX server instance is startedGUI: Go to ''Database'' → ''Export'', choose the target directory 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, press ''OK''.* XQuery: Use {{Function|Database|db:open, etc.) as long as no other database is opened/created by the serverexport}}.* You can force an ordinary WebDAV: Locate the database to being copied to memory by using <code>db:opendirectory ('some-db'or a subdirectory of it) update {}</code>and copy all contents to another location.
=Main-Memory Databases= 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 'Notehelp' to 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.
