Package de.lmu.ifi.dbs.elki.database.ids

Database object identification and ID group handling API.

See:
Description

Interface Summary

ArrayDBIDs	Interface for array based DBIDs.
ArrayModifiableDBIDs	Array-oriented implementation of a modifiable DBID collection.
ArrayStaticDBIDs	Unmodifiable, indexed DBIDs.
DBID	Database ID object.
DBIDFactory	Factory interface for generating DBIDs.
DBIDPair	Immutable pair of two DBIDs.
DBIDRange	Static DBID range.
DBIDs	Interface for a collection of database references (IDs).
HashSetDBIDs	Hash-organized DBIDs
HashSetModifiableDBIDs	Set-oriented implementation of a modifiable DBID collection.
ModifiableDBIDs	Interface for a generic modifiable DBID collection.
SetDBIDs	Interface for DBIDs that support fast "set" operations, in particular "contains" lookups.
StaticDBIDs	Unmodifiable DBIDs.
TreeSetDBIDs	Marker for sorted, tree-organized DBIDs
TreeSetModifiableDBIDs	Set-oriented implementation of a modifiable DBID collection.

Class Summary

DBIDUtil	DBID Utility functions.
EmptyDBIDs	Empty DBID collection.

Package de.lmu.ifi.dbs.elki.database.ids Description

Database object identification and ID group handling API. Database IDs (short: DBID) in ELKI are based on the factory pattern, to allow replacing the simple Integer-based DBIDs with more complex implementations, e.g. for use with external databases or to add tracking for debugging purposes. This also allows adding of more efficient implementations later on in a single place.

DBID interface:

The DBID object identifies a single object. The DBIDs hierarchy contains classes for handling groups (sets, arrays) of IDs, that can be seen as a two-dimensional matrix consisting

	ArrayDBIDs	HashSetDBIDs	TreeSetDBIDs
ModifiableDBIDs	ArrayModifiableDBIDs	HashSetModifiableDBIDs	TreeSetModifiableDBIDs
StaticDBIDs	ArrayStaticDBIDs	n/a	n/a

StaticDBIDs are structures that cannot support modifications, but thus can be implemented more efficiently, for example as Interval. They are mostly used by the data sources. These interfaces cannot be instantiated, obviously. Instead, use the static DBIDFactory.FACTORY, which is also wrapped in the DBIDUtil class.

Examples:

DBIDs allids = database.getIDs();
 // preallocate an array of initial capacity 123 
 ArrayModifiableDBIDs array = DBIDUtil.newArraySet(123);
 // new DBID hash set with minimum initial capacity
 ModifiableDBIDs hash = DBIDUtil.newHashSet();
 // initialize a tree set with the IDs of the database.
 ModifiableDBIDs tree = DBIDUtil.newTreeSet(database.getIDs());
 
 // add all DBIDs from the hash
 tree.addDBIDs(hash)
 

Utility functions:

The static DBIDUtil class provides various utility functions, including:

• DBIDUtil.ensureArray to ensure ArrayDBIDs
• DBIDUtil.ensureModifiable to ensure ModifiableDBIDS
• DBIDUtil.makeUnmodifiable to wrap DBIDs unmodifiable (UnmodifiableDBIDs

Generic utility classes:

MergedDBIDs allows virtual concatenation of multiple DBIDs objects.

MaskedDBIDs allows masking an ArrayDBIDs with a BitSet.