Class ScrollableQueryResult<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList<E>

org.datanucleus.store.query.AbstractQueryResult<E>

org.datanucleus.store.rdbms.query.AbstractRDBMSQueryResult<E>

org.datanucleus.store.rdbms.query.ScrollableQueryResult<E>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, List<E>, SequencedCollection<E>, org.datanucleus.store.query.QueryResult<E>

public final class ScrollableQueryResult<E>
extends AbstractRDBMSQueryResult<E>
implements Serializable

Lazy collection results from a Query with the ResultSet scrollable. Supports the following query extensions (in addition to those supported by superclasses) :-

• datanucleus.query.resultCacheType Type of caching of result objects. Supports strong, weak, soft, none

If there is no transaction present, or if the FetchPlan is in "greedy" mode, and where caching is being used will load all results at startup. Otherwise results are only loaded when accessed.

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private class	ScrollableQueryResult.QueryResultIterator	An Iterator results of a pm.query.execute().iterator()

Field Summary

Fields

Modifier and Type	Field	Description
(package private) int	endIndex	Position of last result (origin=0, set when known).
protected Map<Integer,Object>	resultIdsByPosition	Map of persistable object id, keyed by the result position (0, 1, 2, ...).
private Map<Integer,E>	resultsObjsByIndex	Map of ResultSet object values, keyed by the list index ("0", "1", etc).
(package private) int	startIndex	Position of first result (origin=0).

Fields inherited from class AbstractRDBMSQueryResult

applyRangeChecks, bulkLoadedMmds, bulkLoadedValueByMemberNumber, closeStatementWithResultSet, fp, rof, rs

Fields inherited from class org.datanucleus.store.query.AbstractQueryResult

api, closed, connectionListeners, loadResultsAtCommit, query, resultSizeMethod, size

Fields inherited from class AbstractList

modCount

Constructor Summary

Constructors

Constructor	Description
ScrollableQueryResult(org.datanucleus.store.query.Query query, ResultObjectFactory<E> rof, ResultSet rs, org.datanucleus.FetchPlan fp, Collection candidates)	Constructor of the result from a Query.

Method Summary

Modifier and Type	Method	Description
protected void	cacheQueryResults()
void	close()	Method to close the results, making the results unusable thereafter.
protected void	closingConnection()	Inform the query result that the connection is being closed so perform any operations now, or rest in peace.
boolean	equals(Object o)
E	get(int index)	Method to retrieve a particular element from the list.
protected E	getObjectForIndex(int index)	Accessor for the result object at an index.
protected int	getSizeUsingMethod()	Method to get the size using the "resultSizeMethod".
int	hashCode()
void	initialise()
Iterator<E>	iterator()	Accessor for an iterator for the results.
ListIterator<E>	listIterator()	Accessor for an iterator for the results.
protected void	loadObjects(int start, int maxNumber)	Convenience method to load up rows starting at the specified position.
Object[]	toArray()
<T> T[]	toArray(T[] a)
private <T> T[]	toArrayInternal(T[] a)
protected Object	writeReplace()	Handle serialisation by returning a java.util.ArrayList of all of the results for this query after disconnecting the query which has the consequence of enforcing the load of all objects.

Methods inherited from class AbstractRDBMSQueryResult

closeResults, disconnect, registerMemberBulkResultSet, setCloseStatementWithResultSet

Methods inherited from class org.datanucleus.store.query.AbstractQueryResult

add, add, addAll, addConnectionListener, assertIsOpen, clear, contains, containsAll, indexOf, isEmpty, isOpen, lastIndexOf, remove, set, size, subList

Methods inherited from class AbstractList

listIterator, removeRange

Methods inherited from class AbstractCollection

addAll, remove, removeAll, retainAll, toString

Methods inherited from class Object

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

Methods inherited from interface Collection

parallelStream, removeIf, stream, toArray

Methods inherited from interface Iterable

forEach

Methods inherited from interface List

addAll, addFirst, addLast, getFirst, getLast, remove, removeAll, removeFirst, removeLast, replaceAll, retainAll, reversed, sort, spliterator

Field Details

resultsObjsByIndex

private Map<Integer,E> resultsObjsByIndex

Map of ResultSet object values, keyed by the list index ("0", "1", etc).

resultIdsByPosition

protected Map<Integer,Object> resultIdsByPosition

Map of persistable object id, keyed by the result position (0, 1, 2, ...).

startIndex

int startIndex

Position of first result (origin=0).

endIndex

int endIndex

Position of last result (origin=0, set when known).

Constructor Details

ScrollableQueryResult

public ScrollableQueryResult(org.datanucleus.store.query.Query query,
 ResultObjectFactory<E> rof,
 ResultSet rs,
 org.datanucleus.FetchPlan fp,
 Collection candidates)

Constructor of the result from a Query.

Parameters:

query - The Query

rof - The factory to retrieve results from

rs - The ResultSet from the Query Statement

fp - FetchPlan

candidates - the Candidates collection. Pass this argument only when distinct = false

Method Details

initialise

public void initialise()

Specified by:

initialise in class AbstractRDBMSQueryResult<E>

loadObjects

protected void loadObjects(int start,
 int maxNumber)

Convenience method to load up rows starting at the specified position. Optionally takes a maximum number of rows to process.

Parameters:

start - Start row

maxNumber - Max number to process (-1 means no maximum)

getObjectForIndex

protected E getObjectForIndex(int index)

Accessor for the result object at an index. If the object has already been processed will return that object, otherwise will retrieve the object using the factory.

Parameters:

index - The list index position

Returns:

The result object

close

public void close()

Method to close the results, making the results unusable thereafter.

Specified by:

close in interface org.datanucleus.store.query.QueryResult<E>

Overrides:

close in class AbstractRDBMSQueryResult<E>

closingConnection

protected void closingConnection()

Inform the query result that the connection is being closed so perform any operations now, or rest in peace.

Specified by:

closingConnection in class org.datanucleus.store.query.AbstractQueryResult<E>

cacheQueryResults

protected void cacheQueryResults()

iterator

public Iterator<E> iterator()

Accessor for an iterator for the results.

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface List<E>

Specified by:

iterator in class org.datanucleus.store.query.AbstractQueryResult<E>

Returns:

The iterator

listIterator

public ListIterator<E> listIterator()

Accessor for an iterator for the results.

Specified by:

listIterator in interface List<E>

Specified by:

listIterator in class org.datanucleus.store.query.AbstractQueryResult<E>

Returns:

The iterator

equals

public boolean equals(Object o)

Specified by:

equals in interface Collection<E>

Specified by:

equals in interface List<E>

Overrides:

equals in class AbstractRDBMSQueryResult<E>

hashCode

public int hashCode()

Specified by:

hashCode in interface Collection<E>

Specified by:

hashCode in interface List<E>

Overrides:

hashCode in class AbstractRDBMSQueryResult<E>

get

public E get(int index)

Method to retrieve a particular element from the list.

Specified by:

get in interface List<E>

Specified by:

get in class org.datanucleus.store.query.AbstractQueryResult<E>

Parameters:

index - The index of the element

Returns:

The element at index

getSizeUsingMethod

protected int getSizeUsingMethod()

Method to get the size using the "resultSizeMethod". This implementation supports "LAST" method. Override this in subclasses to implement other methods.

Overrides:

getSizeUsingMethod in class org.datanucleus.store.query.AbstractQueryResult<E>

Returns:

The size

toArray

public Object[] toArray()

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Overrides:

toArray in class org.datanucleus.store.query.AbstractQueryResult<E>

toArray

public <T> T[] toArray(T[] a)

Specified by:

toArray in interface Collection<E>

Specified by:

toArray in interface List<E>

Overrides:

toArray in class org.datanucleus.store.query.AbstractQueryResult<E>

toArrayInternal

private <T> T[] toArrayInternal(T[] a)

writeReplace

protected Object writeReplace()
                       throws ObjectStreamException

Handle serialisation by returning a java.util.ArrayList of all of the results for this query after disconnecting the query which has the consequence of enforcing the load of all objects.

Returns:

The object to serialise

Throws:

ObjectStreamException - thrown if an error occurs