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

Database object identification and ID group handling API.

See: Description

Interface Summary

Interface	Description
ArrayDBIDs	Interface for array based DBIDs.
ArrayModifiableDBIDs	Array-oriented implementation of a modifiable DBID collection.
ArrayStaticDBIDs	Unmodifiable, indexed DBIDs.
DBID	Database ID object.
DBIDArrayIter	Array iterators that can also go backwards and seek.
DBIDArrayMIter	Modifiable array iterator.
DBIDFactory	Factory interface for generating DBIDs.
DBIDIter	Iterator for DBIDs.
DBIDMIter	Modifiable DBID iterator.
DBIDPair	Immutable pair of two DBIDs, more memory efficient than two DBIDs.
DBIDRange	Static DBID range.
DBIDRef	Some object referencing a DBID.
DBIDs	Interface for a collection of database references (IDs).
DBIDVar	(Persistent) variable storing a DBID reference.
DoubleDBIDList	Collection of double values associated with objects.
DoubleDBIDList.Consumer	Consumer for (DBIDRef, double) pairs.
DoubleDBIDListIter	Iterator over double-DBID pairs results.
DoubleDBIDListMIter	Modifiable DBIDList iterator.
DoubleDBIDPair	Pair of a double value and a DBID.
HashSetDBIDs	Hash-organized DBIDs
HashSetModifiableDBIDs	Set-oriented implementation of a modifiable DBID collection.
KNNHeap	Interface for kNN heaps.
KNNList	Interface for kNN results.
ModifiableDBIDs	Interface for a generic modifiable DBID collection.
ModifiableDoubleDBIDList	Modifiable API for Distance-DBID results
SetDBIDs	Interface for DBIDs that support fast "set" operations, in particular "contains" lookups.
StaticDBIDs	Unmodifiable DBIDs.

Class Summary

Class	Description
DBIDUtil	DBID Utility functions.
EmptyDBIDs	Empty DBID collection.
EmptyDBIDs.EmptyDBIDIterator	Iterator for empty DBIDs-
QuickSelectDBIDs	QuickSelect computes ("selects") the element at a given rank and can be used to compute Medians and arbitrary quantiles by computing the appropriate rank.

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
ModifiableDBIDs	ArrayModifiableDBIDs	HashSetModifiableDBIDs
StaticDBIDs	ArrayStaticDBIDs	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();
 
 // add all DBIDs from the hash
 tree.addDBIDs(hash)
 

Utility functions:

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