From BaseX Documentation
This page is part of the Getting Started Section.
In BaseX, a database is a pretty light-weight concept and can be compared to a collection. It contains an arbitrary number of resources, addressed by their unique database path. Resources can either be XML documents or raw files (binaries). Some information on binary data can be found on an extra page.
New databases can be created via commands, in the GUI, or with any of our APIs. If some input is specified along with the create operation, it will be added to the database in a bulk operation:
CREATE DB db /path/to/resourceswill add initial documents to a database
- GUI: Go to Database → New, press Browse to choose an initial file or directory, and press OK
Note: A main-memory only database can be created using the the
SET MAINMEM true command before calling
CREATE DB (see below for more).
Stored resources and external documents can be accessed in different ways:
Various XQuery functions exist to access XML documents in databases:
|Returns all documents that are found in the database |
|Returns all documents at the location |
If no path is specified after the database, all documents in the database will be returned.
If no argument is specified, all documents of the database will be returned that has been opened in the global context.
|Returns the document at the location |
An error is raised if the specified yields zero or more than one document.
You can access multiple databases in a single query:
for $i in 1 to 100 return db:open('books' || $i)//book/title
If the DEFAULTDB option is turned on, the path argument of the
fn:collection function will first be resolved against the globally opened database.
Two more functions are available for retrieving information on database nodes:
|Returns the name of the database in which the specified |
|Returns the path of the database document in which the specified |
fn:base-uri functions return URIs that can also be reused as arguments for the
fn:collection functions. As a result, the following example query always returns
every $c in collection('anyDB') satisfies doc-available(document-uri($c))
If the argument of
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.
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
WRITEBACKoption is set.
collection("/path/to/docs"): returns a main-memory collection with all XML documents found at the addressed file path.
Updated with Version 8.4: items of binary type can be output without specifying the obsolete
raw serialization method.
If the API you use does not support binary output (this is e.g. the case for various Client language bindings), you need to convert your binary data to its string representation before returning it to the client:
- 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.
Once you have created a database, additional commands exist to modify its contents:
- XML documents can be added with the
- Raw files are added with
- Existing resources can be replaced with the
- Resources can be deleted via
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 ADDCACHE option will first cache the input before adding it to the database. This is helpful when the input documents to be added are expected to eat up too much main memory.
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 SET ADDCACHE true ADD /path/to/xml/documents STORE TO images/ 123.jpg FLUSH DELETE /
You may as well use the BaseX-specific XQuery Database Functions to create, 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.
All resources stored in a database can be exported, i.e., written back to disk. This can be done in several ways:
EXPORTwrites 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
In Memory Database
- In the standalone context, a main-memory database can be created (using
CREATE DB), 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
CREATE DB), 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.
Note: main-memory database instances are also created by the invocation of
collection(...), if the argument is not a
database (no matter which value is set for MAINMEM). In other words:
the same internal representation is used for main-memory databases and
documents/collections generated via XQuery.
- Version 8.4
- Updated: Raw Files: Items of binary type can be output without specifying the obsolete
- Version 7.2.1
fn:base-urinow return strings that can be reused with
fn:collectionto reopen the original document.