Changes

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.

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| Introduced with {{Announce|Version 10}}: 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]].|}

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''

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.

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|-valign="top"|{{Function|Database|db:openget}}|{{Code|db:openget("db", "path/to/docs")}}

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return db:openget('books' || $i)//book/title

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==Binary FilesData==

The {{Command|RETRIEVEBINARY GET}} command and the {{Function|Database|db: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:

==HTTP ServicesXQuery Values==

* With [[REST]] and [[WebDAV]]{{Function|Database|db:get-value}}, all database resources XQuery values can be requested retrieved. In the following example, we assume that an XQuery map {{Code|cities}} was stored in a uniform wayan {{Code|indexes}} database: <syntaxhighlight 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</syntaxhighlight>

* XML documents can be added with the {{Command|ADDPUT}} command.* Raw files are added with and {{Command|STOREADD}}commands.* Existing resources can be replaced Binary data is stored with the {{Command|BINARY PUT}} command.* Resources of all types can be deleted via {{Command|DELETE}}.

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).

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.

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/

==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:

let $root db:= "add('documents', '/path/to/xml/documentsresources/"for $file in file:list($root)return db:add("database", $root || $file')

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 ''Database'' menu.error message is stored as a string value:

<syntaxhighlight lang="xquery">let $db := 'documents'let $root := '/path/to/resources/'for $path in file:list($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 || '.error')}</syntaxhighlight> The error messages can e.g. be analyzed in a second step: <syntaxhighlight lang="xquery">let $errors := db:get-value('documents')for $filename in map:keys($errors)where ends-with($filename, '.error')return $filename || ': ' || $errors?($filename)</syntaxhighlight> =Export Database= All resources stored in a database can be ''exported'', i.e., written back to disk, e.g., as follows: * Commands: {{Command|EXPORT}} writes all resources to the specified target directory.* GUI: Go to ''Database'' → ''Export Data'', 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. =Main-Memory Databases=

All resources stored 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 ''exported''created, i.e., written back to disk. This which can then be done in several ways:accessed by subsequent commands.

* 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|EXPORTCREATE DB}} writes all resources to the specified target directory* GUI: Go to ''Database'' → ''Export''call, choose the target directory BaseX clients can then access and press ''OK''* WebDAVupdate this database: Locate the database directory (or a sub-directory of it) and copy all contents to another location

<syntaxhighlight lang=Main"perl"># Serverbasexserver -Memory c"SET mainmem on" -c"CREATE DB mainmem document.xml"BaseX [Server]Server was started (port: 1984).MAINMEM: trueDatabase Instances='mainmem' created in 1782.80 ms.

* In the standalone context, a main-memory database can be created (using <code>CREATE DB</code>), which can then be accessed by subsequent commands# ClientbasexclientUsername: ...* 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, dbPassword:open, etc.) as long as no other database is opened/created by the server..* You can force an ordinary database BaseX [Client]Try 'help' to being copied to memory by using <codeget more information.>XQUERY count(db:openget('some-dbmainmem') update {}//*)1876462Query executed in 0.97 ms.</codesyntaxhighlight>

'''NoteAdditional 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}}).

 * Updated: [[#Raw Files|Raw Files]]: Items of binary type can be output without specifying the obsolete <code>raw</code> serialization method.