Package org.apache.lucene.facet.taxonomy.writercache

Class CompactLabelToOrdinal

java.lang.Object

org.apache.lucene.facet.taxonomy.writercache.LabelToOrdinal

org.apache.lucene.facet.taxonomy.writercache.CompactLabelToOrdinal

public class CompactLabelToOrdinal
extends LabelToOrdinal

This is a very efficient LabelToOrdinal implementation that uses a CharBlockArray to store all labels and a configurable number of HashArrays to reference the labels.

Since the HashArrays don't handle collisions, a CollisionMap is used to store the colliding labels.

This data structure grows by adding a new HashArray whenever the number of collisions in the CollisionMap exceeds loadFactor * LabelToOrdinal.getMaxOrdinal(). Growing also includes reinserting all colliding labels into the HashArrays to possibly reduce the number of collisions. For setting the loadFactor see CompactLabelToOrdinal(int, float, int).

This data structure has a much lower memory footprint (~30%) compared to a Java HashMap<String, Integer>. It also only uses a small fraction of objects a HashMap would use, thus limiting the GC overhead. Ingestion speed was also ~50% faster compared to a HashMap for 3M unique labels.

Field Summary

Fields

Modifier and Type	Field	Description
static final float	DefaultLoadFactor	Default maximum load factor.

Fields inherited from class org.apache.lucene.facet.taxonomy.writercache.LabelToOrdinal

INVALID_ORDINAL

Constructor Summary

Constructors

Constructor	Description
CompactLabelToOrdinal(int initialCapacity, float loadFactor, int numHashArrays)	Sole constructor.

Method Summary

Modifier and Type	Method	Description
void	addLabel(FacetLabel label, int ordinal)	Adds a new label if its not yet in the table.
int	getOrdinal(FacetLabel label)	Returns the ordinal assigned to the given label, or LabelToOrdinal.INVALID_ORDINAL if the label cannot be found in this table.
int	sizeOfMap()	How many labels.

Methods inherited from class org.apache.lucene.facet.taxonomy.writercache.LabelToOrdinal

getMaxOrdinal, getNextOrdinal

Methods inherited from class java.lang.Object

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

Field Details

DefaultLoadFactor

public static final float DefaultLoadFactor

Default maximum load factor.

See Also:

• Constant Field Values

Constructor Details

CompactLabelToOrdinal

public CompactLabelToOrdinal(int initialCapacity,
 float loadFactor,
 int numHashArrays)

Sole constructor.

Method Details

sizeOfMap

public int sizeOfMap()

How many labels.

addLabel

public void addLabel(FacetLabel label,
 int ordinal)

Description copied from class: LabelToOrdinal

Adds a new label if its not yet in the table. Throws an IllegalArgumentException if the same label with a different ordinal was previoulsy added to this table.

Specified by:

addLabel in class LabelToOrdinal

getOrdinal

public int getOrdinal(FacetLabel label)

Description copied from class: LabelToOrdinal

Returns the ordinal assigned to the given label, or LabelToOrdinal.INVALID_ORDINAL if the label cannot be found in this table.

Specified by:

getOrdinal in class LabelToOrdinal