alluxio.collections

Class IndexDefinition<T,V>

java.lang.Object

alluxio.collections.IndexDefinition<T,V>

Type Parameters:

T - the type that this is an index for

V - the type of the value used for indexing

@ThreadSafe
public abstract class IndexDefinition<T,V>
extends Object

A class representing an index for an IndexedSet. For example, if an indexed set stores inodes, and we want to be able to look them up by their "id" field, we would define an index like so:

 public class IndexDefinition<Inode, Long>() {
   @Override
   Long getFieldValue(Inode) {
     return Inode.getId();
   }
 }
 

Constructor Summary

Constructors

Constructor and Description
IndexDefinition(boolean isUnique) Constructs a new IndexDefinition instance.

Method Summary

Modifier and Type	Method and Description
abstract V	getFieldValue(T o) Gets the value of the field that serves as index.
boolean	isUnique()
static <T,V> IndexDefinition<T,V>	ofNonUnique(java.util.function.Function<T,V> definition) Creates a new, non-unique index definition.
static <T,V> IndexDefinition<T,V>	ofUnique(java.util.function.Function<T,V> definition) Creates a new, unique index definition.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

IndexDefinition

public IndexDefinition(boolean isUnique)

Constructs a new IndexDefinition instance.

Parameters:

isUnique - whether the index is unique. A unique index is an index where each index value only maps to one object; A non-unique index is an index where an index value can map to one or more objects.

Method Detail

isUnique

public boolean isUnique()

Returns:

whether the index requires all field values to be unique

getFieldValue

public abstract V getFieldValue(T o)

Gets the value of the field that serves as index.

Parameters:

o - the instance to get the field value from

Returns:

the field value

ofUnique

public static <T,V> IndexDefinition<T,V> ofUnique(java.util.function.Function<T,V> definition)

Creates a new, unique index definition.

Type Parameters:

T - the element type in the indexed set

V - the index type

Parameters:

definition - the mapping function that maps an indexed element in the set to its index

Returns:

the unique definition

ofNonUnique

public static <T,V> IndexDefinition<T,V> ofNonUnique(java.util.function.Function<T,V> definition)

Creates a new, non-unique index definition.

Type Parameters:

T - the element type in the indexed set

V - the index type

Parameters:

definition - the mapping function that maps an indexed element in the set to its index

Returns:

the non-unique definition