Difference between revisions of "Databases"

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Valid database names may contain letters, numbers,
Valid database names may contain letters, numbers,
underslashes and dashes (defined by the regular expression <code>[_-a-zA-Z0-9]+</code>).
underslashes and dashes (defined by the regular expression <code>[-_a-zA-Z0-9]+</code>).
==Manage Resources==
==Manage Resources==

Revision as of 14:04, 25 December 2011

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.

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 DatabaseNew, 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 DatabaseManage and choose the database to be dropped

Valid database names may contain letters, numbers, underslashes and dashes (defined by the regular expression [-_a-zA-Z0-9]+).

Manage 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
ADD example.xml
ADD ...
STORE TO images/ 123.jpg

You may as well use the BaseX-specific XQuery Database Functions to add, replace and delete XML documents:

for $file in file:list("/path/to/xml/documents")
return db:add("database", $file)

Last but not least, XML documents can also be added via the GUI and the Database menu.

Access Resources

Stored resources and external documents can be accessed in different ways:

XML Documents

Various XQuery functions exist to access the XML documents in databases and other locations:

  • db:open("dbname", "path/to/docs"): (only) returns documents that are found in the specified database.
  • collection("path/to/docs"): returns the documents that are either found in the database specified in the argument, or at the specified location (file path or URL).
  • doc("path/to/document.xml"): returns a single document found at the specified location (file path or URL). If a database already exists for the addressed resource, it is opened instead.

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 raw form:
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.

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 DatabaseExport, 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