Difference between revisions of "Databases"
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|- | |- | ||
!Function | !Function | ||
+ | !Example | ||
!Description | !Description | ||
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|- | |- | ||
− | + | |<code>[[Database Module#db:open|db:open()]]</code> | |
− | + | |{{Mono|db:open("db", "path/to/tocs")}} | |
− | |Returns all documents that are found in the | + | |Returns all documents that are found in the database {{Mono|db}} at the (optional) path {{Mono|path/to/docs}}. |
|- | |- | ||
− | + | |<code>[http://www.xqueryfunctions.com/xq/fn_collection.html fn:collection()]</code> | |
− | + | |{{Mono|collection("db/path/to/docs")}} | |
− | |Returns all documents at the location {{Mono|path/to/docs}} in the database {{Mono|db}}. All documents in the database are returned if no path is specified. | + | |Returns all documents at the location {{Mono|path/to/docs}} in the database {{Mono|db}}.<br/>All documents in the database are returned if no path is specified. |
|- | |- | ||
− | + | |<code>[http://www.xqueryfunctions.com/xq/fn_doc.html fn:doc()]</code> | |
− | + | |{{Mono|doc("db/path/to/doc.xml")}} | |
− | |Returns the document at the location {{Mono|path/to/docs}} in the database {{Mono|db}}. An error is raised if the specified addresses does not address exactly one document. | + | |Returns the document at the location {{Mono|path/to/docs}} in the database {{Mono|db}}.<br/>An error is raised if the specified addresses does not address exactly one document. |
|} | |} | ||
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* {{Mono|doc("http://web.de")}}: retrieves the addressed URI and returns it as a main-memory document node. | * {{Mono|doc("http://web.de")}}: retrieves the addressed URI and returns it as a main-memory document node. | ||
− | * {{Mono|collection("/path/to/docs")}}: returns a main-memory collection with all XML documents found | + | * {{Mono|collection("/path/to/docs")}}: returns a main-memory collection with all XML documents found at the addressed file path. |
==Raw Files== | ==Raw Files== |
Revision as of 00:20, 26 April 2012
This page is part of the Getting Started Section.
In BaseX, a single database contains an arbitrary number of resources, addressed by their unique database path. Since Version 7.0, resources can either be XML documents or raw files (binaries). Sets of XML documents are also called collections. Some information on binary data can be found on an extra page.
Contents
Create/Drop Database
New databases can either be created in the GUI, on command line, or using any of our APIs. XML documents can be specified along with the create operation, which will be added to the database in a bulk operation:
- Console: enter
basex -c "CREATE DB dbname /path/to/resources"
- GUI: Go to Database → New, press Browse to choose an initial file or directory, and press OK
Various parsers can be chosen to influence the database creation, or to convert different formats to XML.
Existing databases can eventually be dropped again:
- Console: enter
basex -c "DROP DB dbname"
. - GUI: Go to Database → Manage and choose the database to be dropped
Database must follow the valid names constraints.
Access Resources
Stored resources and external documents can be accessed in different ways:
XML Documents
Various XQuery functions exist to access XML documents in databases and from other locations:
Function | Example | Description |
---|---|---|
db:open()
|
db:open("db", "path/to/tocs")
|
Returns all documents that are found in the database db at the (optional) path path/to/docs .
|
fn:collection()
|
collection("db/path/to/docs")
|
Returns all documents at the location path/to/docs in the database db .All documents in the database are returned if no path is specified. |
fn:doc()
|
doc("db/path/to/doc.xml")
|
Returns the document at the location path/to/docs in the database db .An error is raised if the specified addresses does not address exactly one document. |
The fn:document-uri()
and fn:base-uri()
functions returns paths that can be reused as arguments for the fn:doc()
and fn:collection()
functions.
If the argument of fn:doc()
or 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:
doc("http://web.de")
: retrieves the addressed URI and returns it as a main-memory document node.collection("/path/to/docs")
: returns a main-memory collection with all XML documents found at the addressed file path.
Raw Files
- XQuery:
db:retrieve("dbname", "path/to/docs")
returns raw files in their Base64 representation. By choosing"method=raw"
as Serialization Option, the data is returned in its original byte representation:
declare option output:method "raw"; db:retrieve('multimedia', 'sample.avi')
- Commands:
RETRIEVE
returns raw files without modifications.
HTTP Services
- With REST and WebDAV, all database resources can be requested in a uniform way, no matter if they are well-formed XML documents or binary files.
Update Resources
Once you have created a database, additional commands exist to modify its contents:
- XML documents can be added with the
ADD
command. - Raw files are added with
STORE
. - Resource can be replaced with other ones with the
REPLACE
command. - Resources can be deleted via
DELETE
.
The AUTOFLUSH option can be turned off before bulk operations (i.e. before a large number of new resources is added to the database).
The following commands create an empty database, add two resources, explicitly flush data structures to disk, and finally delete all inserted data:
CREATE DB example SET AUTOFLUSH false ADD example.xml ADD ... STORE TO images/ 123.jpg FLUSH DELETE /
You may as well use the BaseX-specific XQuery Database Functions to add, replace and delete XML documents:
let $root := "/path/to/xml/documents/" for $file in file:list($root) return db:add("database", $root || $file)
Last but not least, XML documents can also be added via the GUI and the Database menu.
Export Data
All resources stored in a database can be exported, i.e., written back to disk. This can be done in several ways:
- Commands:
EXPORT
writes all resources to the specified target directory - GUI: Go to 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
Changelog
Version 7.2.1
- Updated:
fn:document-uri()
andfn:base-uri()
now return strings that can be reused withfn:doc()
orfn:collection()
to reopen the original document.