Class MemStatementIterator

java.lang.Object

org.eclipse.rdf4j.sail.memory.model.MemStatementIterator

All Implemented Interfaces:

AutoCloseable, CloseableIteration<MemStatement, SailException>, Iteration<MemStatement, SailException>

public class MemStatementIterator
extends Object
implements CloseableIteration<MemStatement, SailException>

A StatementIterator that can iterate over a list of Statement objects. This iterator compares Resource and Literal objects using the '==' operator, which is possible thanks to the extensive sharing of these objects in the MemoryStore.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	MemStatementIterator.Stats

Field Summary

Fields

Modifier and Type	Field	Description
private int	cachedHashCode
private boolean	closed	Flag indicating whether this iteration has been closed.
private final MemResource[]	contexts	The context of statements to return, or null if any context is OK.
private final boolean	explicit	Flag indicating whether this iterator should only return explicitly added statements or only return inferred statements.
private final boolean	explicitNotSpecified
private final MemStatementIteratorCache	iteratorCache
private int	matchingStatements	The number of returned statements
static final int	MIN_SIZE_TO_CONSIDER_FOR_CACHE
private MemStatement	nextElement
private final boolean	noIsolation
private final MemValue	object	The object of statements to return, or null if any object is OK.
private final MemIRI	predicate	The predicate of statements to return, or null if any predicate is OK.
private final int	snapshot	Indicates which snapshot should be iterated over.
private int	statementIndex	The index of the last statement that has been returned.
private MemStatement[]	statementList
private final int	statementListSize	The lists of statements over which to iterate, and its size (different from length).
private final MemResource	subject	The subject of statements to return, or null if any subject is OK.

Constructor Summary

Constructors

Constructor	Description
MemStatementIterator(MemStatementList statementList, MemResource subject, MemIRI predicate, MemValue object, Boolean explicit, int snapshot, MemStatementIteratorCache iteratorCache, MemResource... contexts)	Creates a new MemStatementIterator that will iterate over the statements contained in the supplied MemStatementList searching for statements that match the specified pattern of subject, predicate, object and context(s).

Method Summary

Modifier and Type	Method	Description
static CloseableIteration<MemStatement, SailException>	cacheAwareInstance(MemStatementList smallestList, MemResource subj, MemIRI pred, MemValue obj, Boolean explicit, int snapshot, MemResource[] memContexts, MemStatementIteratorCache iteratorCache)
final void	close()	Closes this iteration, freeing any resources that it is holding.
boolean	equals(Object o)
private MemStatement	getNextElement()	Searches through statementList, starting from index _nextStatementIdx + 1, for statements that match the constraints that have been set for this iterator.
MemStatementIterator.Stats	getStats()
int	hashCode()
final boolean	hasNext()	Returns true if the iteration has more elements.
private boolean	isCandidateForCache()	Returns true if this iterator was particularly costly and should be considered for caching
private MemStatement	lookAhead()	Fetches the next element if it hasn't been fetched yet and stores it in nextElement.
(package private) boolean	matchesExplicitAndSnapshot(MemStatement st)
final MemStatement	next()	Returns the next element in the iteration.
void	remove()	Throws an UnsupportedOperationException.
String	toString()

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface CloseableIteration

stream

Field Details

MIN_SIZE_TO_CONSIDER_FOR_CACHE

public static final int MIN_SIZE_TO_CONSIDER_FOR_CACHE

See Also:

• Constant Field Values

statementListSize

private final int statementListSize

The lists of statements over which to iterate, and its size (different from length). Always set the size before the array. If we get the array first and the size after, then the MemStatementList object could have resized the array in between so that the size > length.

statementList

private MemStatement[] statementList

subject

private final MemResource subject

The subject of statements to return, or null if any subject is OK.

predicate

private final MemIRI predicate

The predicate of statements to return, or null if any predicate is OK.

object

private final MemValue object

The object of statements to return, or null if any object is OK.

contexts

private final MemResource[] contexts

The context of statements to return, or null if any context is OK.

explicit

private final boolean explicit

Flag indicating whether this iterator should only return explicitly added statements or only return inferred statements.

If this has not been specified (null) and we should return both explicit and inferred statements, then the flag below will be set to true.

explicitNotSpecified

private final boolean explicitNotSpecified

snapshot

private final int snapshot

Indicates which snapshot should be iterated over.

noIsolation

private final boolean noIsolation

statementIndex

private int statementIndex

The index of the last statement that has been returned.

matchingStatements

private int matchingStatements

The number of returned statements

nextElement

private MemStatement nextElement

closed

private boolean closed

Flag indicating whether this iteration has been closed.

iteratorCache

private final MemStatementIteratorCache iteratorCache

cachedHashCode

private int cachedHashCode

Constructor Details

MemStatementIterator

public MemStatementIterator(MemStatementList statementList,
 MemResource subject,
 MemIRI predicate,
 MemValue object,
 Boolean explicit,
 int snapshot,
 MemStatementIteratorCache iteratorCache,
 MemResource... contexts)
                     throws InterruptedException

Creates a new MemStatementIterator that will iterate over the statements contained in the supplied MemStatementList searching for statements that match the specified pattern of subject, predicate, object and context(s).

Parameters:

statementList - the statements over which to iterate.

subject - subject of pattern.

predicate - predicate of pattern.

object - object of pattern.

contexts - context(s) of pattern.

Throws:

InterruptedException

Method Details

cacheAwareInstance

public static CloseableIteration<MemStatement, SailException> cacheAwareInstance(MemStatementList smallestList,
 MemResource subj,
 MemIRI pred,
 MemValue obj,
 Boolean explicit,
 int snapshot,
 MemResource[] memContexts,
 MemStatementIteratorCache iteratorCache)
                                                                          throws InterruptedException

Throws:

InterruptedException

getNextElement

private MemStatement getNextElement()

Searches through statementList, starting from index _nextStatementIdx + 1, for statements that match the constraints that have been set for this iterator. If a matching statement has been found it will be stored in _nextStatement and _nextStatementIdx points to the index of this statement in _statementList. Otherwise, _nextStatement will set to null.

matchesExplicitAndSnapshot

boolean matchesExplicitAndSnapshot(MemStatement st)

isCandidateForCache

private boolean isCandidateForCache()

Returns true if this iterator was particularly costly and should be considered for caching

Returns:

true if it should be cached

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

getStats

public MemStatementIterator.Stats getStats()

hasNext

public final boolean hasNext()

Description copied from interface: Iteration

Returns true if the iteration has more elements. (In other words, returns true if Iteration.next() would return an element rather than throwing a NoSuchElementException.)

Specified by:

hasNext in interface Iteration<MemStatement, SailException>

Returns:

true if the iteration has more elements.

next

public final MemStatement next()

Description copied from interface: Iteration

Returns the next element in the iteration.

Specified by:

next in interface Iteration<MemStatement, SailException>

Returns:

the next element in the iteration.

lookAhead

private MemStatement lookAhead()

Fetches the next element if it hasn't been fetched yet and stores it in nextElement.

Returns:

The next element, or null if there are no more results. @ If there is an issue getting the next element or closing the iteration.

remove

public void remove()

Throws an UnsupportedOperationException.

Specified by:

remove in interface Iteration<MemStatement, SailException>

close

public final void close()

Description copied from interface: CloseableIteration

Closes this iteration, freeing any resources that it is holding. If the iteration has already been closed then invoking this method has no effect.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface CloseableIteration<MemStatement, SailException>