Package nz.org.riskscape.engine.join

Class HashIndexer

java.lang.Object

nz.org.riskscape.engine.join.JoinIndexer

nz.org.riskscape.engine.join.RealizedExpressionJoinIndexer

nz.org.riskscape.engine.join.HashIndexer

public class HashIndexer
extends RealizedExpressionJoinIndexer

JoinIndexer implementation that builds an in-memory hash index of tuples when the JoinCondition is an equality filter. Eg 'lhs.thing = rhs.thing'

Nested Class Summary

Nested classes/interfaces inherited from class nz.org.riskscape.engine.join.JoinIndexer

JoinIndexer.Constructor

Field Summary

Fields

Modifier and Type	Field	Description
static final JoinIndexer.Constructor	CONSTRUCTOR
static final int	DEFAULT_INITIAL_INDEX_SIZE	The default capacity that indexes will be created for.

Fields inherited from class nz.org.riskscape.engine.join.RealizedExpressionJoinIndexer

lhsExpression, operator, rhsExpression

Fields inherited from class nz.org.riskscape.engine.join.JoinIndexer

expressionRealizer, join

Constructor Summary

Constructors

Constructor	Description
HashIndexer(nz.org.riskscape.engine.join.Join join, nz.org.riskscape.engine.rl.ExpressionRealizer expressionRealizer, int initialIndexSize)

Method Summary

Modifier and Type	Method	Description
void	addToIndex(nz.org.riskscape.engine.Tuple toCache)
nz.org.riskscape.engine.relation.TupleIterator	createRhsIterator(nz.org.riskscape.engine.Tuple lhs)	Create a TupleIterator that will contain at least the set of Tuples that are needed to completely join the lhs to the rhs based on the join.
boolean	isUsable()
String	toString()

Methods inherited from class nz.org.riskscape.engine.join.RealizedExpressionJoinIndexer

isAllowed, processIndexableMetadata

Methods inherited from class nz.org.riskscape.engine.join.JoinIndexer

getExpressionRealizer, getJoin

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_INITIAL_INDEX_SIZE

public static final int DEFAULT_INITIAL_INDEX_SIZE

The default capacity that indexes will be created for.

The HashIndexer contains a map of right hand side values to items.

For best performance the index should be as large as the expected number of unique right hand side values.

See Also:

• Constant Field Values

CONSTRUCTOR

public static final JoinIndexer.Constructor CONSTRUCTOR

Constructor Details

HashIndexer

public HashIndexer(nz.org.riskscape.engine.join.Join join,
 nz.org.riskscape.engine.rl.ExpressionRealizer expressionRealizer,
 int initialIndexSize)

Method Details

addToIndex

public void addToIndex(nz.org.riskscape.engine.Tuple toCache)

Specified by:

addToIndex in class JoinIndexer

createRhsIterator

public nz.org.riskscape.engine.relation.TupleIterator createRhsIterator(nz.org.riskscape.engine.Tuple lhs)

Description copied from class: JoinIndexer

Create a TupleIterator that will contain at least the set of Tuples that are needed to completely join the lhs to the rhs based on the join.

Specified by:

createRhsIterator in class JoinIndexer

isUsable

public boolean isUsable()

Overrides:

isUsable in class RealizedExpressionJoinIndexer

Returns:

true if this join can be used, e.g. it's suitable for the query and join. This is intended as a simpler way of providing a set of implementations such that the DefaultJoiner can work through which ones are appropriate by checking this method.

toString

public String toString()

Overrides:

toString in class Object