com.goldencode.p2j.persist

Class Presorter.IncrementalResults

java.lang.Object

com.goldencode.p2j.persist.SimpleResults

com.goldencode.p2j.persist.Presorter.IncrementalResults

All Implemented Interfaces:

SessionListener, FullResults, Presorter.LazyEvaluator, Results

Enclosing class:

Presorter

private class Presorter.IncrementalResults
extends SimpleResults
implements SessionListener, Presorter.LazyEvaluator

This class should be used instead of Presorter.SortedResults when the sort criteria added to the Presorter match the leading components of the presort query sort phrase (i.e. results are already sorted in the proper order). This class retrieves results iteratively on demand which lead to faster initial response / less memory consumption compared to Presorter.SortedResults which caches and sorts all results up front.

If session expires, all remaining results (record IDs) are cached. Break group information in this case will be retrieved iteratively on request.

Nested Class Summary

Nested classes/interfaces inherited from interface com.goldencode.p2j.persist.event.SessionListener

SessionListener.Event, SessionListener.Scope

Field Summary

Fields

Modifier and Type	Field and Description
private Results	backingResults Original sorted results.
private int	backingResultsOffset Offset that is used to determine the row number into the whole result set (global row number = offset + row number into cached result set).
private static java.lang.String	BACKWARD_SCROLL_ERROR Error message if a non-scrolling query is scrolled backward.
private BaseDataType[]	currentBDT Array which contains the sort criteria values for the last loaded row.
private java.lang.Long[]	currentRow Cache for non-scrolling queries.
private int	lastEvaluatedRow Number of the row which corresponds the currentBDT.
private BaseDataType[]	nextBDT Array which contains the sort criteria values for the row after the last loaded row (i.e.
private java.lang.Long[]	nextRow Cache for non-scrolling queries.
private BaseDataType[]	prevBDT Array which contains the sort criteria values for the row before the last loaded row.
private java.lang.Long[]	prevRow Cache for non-scrolling queries.
private boolean	resultsCached Indicates whether backing results have been cached because of session closing.
private int	rowsSize Number of loaded rows (for non-scrolling queries).
private boolean	scrolling Determines whether this Results are scrolling.

Fields inherited from interface com.goldencode.p2j.persist.Results

LOG

Constructor Summary

Constructors

Modifier	Constructor and Description
private	IncrementalResults(Results sorted) Create a result set that will interrogate sorted results iteratively on request.

Method Summary

Modifier and Type	Method and Description
private void	addRow(java.lang.Long[] ids) Store the given record identifiers to the rows cache.
void	cleanup() Clear the internal list of result rows and the backing results.
private void	cleanupBackingResults() Clear the backing results.
void	deregisteredSessionListener() No-op in this implementation.
void	evaluate(int row, boolean firstOf) Evalualte break row(s) which help to determine whether the given row if the first/last in a break group.
boolean	first() Move cursor to the first results row.
java.lang.Object[]	get() Get the array of objects at the current result row.
int	getNumberOfLoadedRows() Returns the number of rows which have been loaded by this Results.
private java.lang.Long[]	getRow(int row) Get the specified row (an array of record identifiers).
private boolean	isFirst(int row) Tests whether the given row is the first row in the results set.
private boolean	isLast(int row) Tests whether the given row is the last row in the results set.
boolean	isResultSetCached() Indicate whether the full result set is cached in this object.
boolean	last() Move cursor to the last results row.
private void	loadBDTIntoArray(java.lang.Long[] ids, BaseDataType[] targetArray) Load sort criteria values using identifiers of corresponding records.
private void	loadRow(int rowNumber) Load the specified row into the cache.
boolean	next() Move cursor to the next results row.
boolean	scroll(int rows) Scroll the cursor ahead by the specified number of rows.
void	sessionClosing() Clears the backing results.
boolean	sessionEvent(SessionListener.Event event) Invoked when a Hibernate session event occurs.
boolean	setRowNumber(int row) Set the row number currently under the cursor.

Methods inherited from class com.goldencode.p2j.persist.SimpleResults

addRow, deleteRow, get, getID, getRowNumber, getRows, isEmpty, isFirst, isLast, previous, reset

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.goldencode.p2j.persist.Results

get, isAutoFetch

Field Detail

BACKWARD_SCROLL_ERROR

private static final java.lang.String BACKWARD_SCROLL_ERROR

Error message if a non-scrolling query is scrolled backward.

See Also:

Constant Field Values

backingResults

private Results backingResults

Original sorted results.

backingResultsOffset

private int backingResultsOffset

Offset that is used to determine the row number into the whole result set (global row number = offset + row number into cached result set).

currentBDT

private BaseDataType[] currentBDT

Array which contains the sort criteria values for the last loaded row.

prevBDT

private BaseDataType[] prevBDT

Array which contains the sort criteria values for the row before the last loaded row.

nextBDT

private BaseDataType[] nextBDT

Array which contains the sort criteria values for the row after the last loaded row (i.e. pre-loaded row).

scrolling

private final boolean scrolling

Determines whether this Results are scrolling.

lastEvaluatedRow

private int lastEvaluatedRow

Number of the row which corresponds the currentBDT.

currentRow

private java.lang.Long[] currentRow

Cache for non-scrolling queries. IDs which correspond with last loaded row.

prevRow

private java.lang.Long[] prevRow

Cache for non-scrolling queries. IDs which correspond with row before last loaded row.

nextRow

private java.lang.Long[] nextRow

Cache for non-scrolling queries. IDs which correspond with row after last loaded row (i.e. pre-loaded row).

rowsSize

private int rowsSize

Number of loaded rows (for non-scrolling queries).

resultsCached

private boolean resultsCached

Indicates whether backing results have been cached because of session closing.

Constructor Detail

IncrementalResults

private IncrementalResults(Results sorted)

Create a result set that will interrogate sorted results iteratively on request.

Parameters:

sorted - Original sorted results.

Method Detail

get

public java.lang.Object[] get()

Get the array of objects at the current result row.

Specified by:

get in interface Results

Overrides:

get in class SimpleResults

Returns:

Object array or null.

first

public boolean first()

Move cursor to the first results row.

Specified by:

first in interface Results

Overrides:

first in class SimpleResults

Returns:

true if there are any results.

last

public boolean last()

Move cursor to the last results row.

Specified by:

last in interface Results

Overrides:

last in class SimpleResults

Returns:

true if there are any results.

next

public boolean next()

Move cursor to the next results row.

Specified by:

next in interface Results

Overrides:

next in class SimpleResults

Returns:

true if there is a result under the cursor under the move.

setRowNumber

public boolean setRowNumber(int row)

Set the row number currently under the cursor.

Specified by:

setRowNumber in interface Results

Overrides:

setRowNumber in class SimpleResults

Parameters:

row - Zero-based index of the row to be set as the current row.

Returns:

true if there is a row at the specified row number; else false.

scroll

public boolean scroll(int rows)

Scroll the cursor ahead by the specified number of rows. If the number is negative, the cursor is moved backward. This may put the cursor off the end (either end) of the query's results.

Specified by:

scroll in interface Results

Overrides:

scroll in class SimpleResults

Parameters:

rows - Number of rows to jump ahead or back.

Returns:

true if there is a row at the new location; else false.

getNumberOfLoadedRows

public int getNumberOfLoadedRows()

Returns the number of rows which have been loaded by this Results.

Specified by:

getNumberOfLoadedRows in interface Results

Overrides:

getNumberOfLoadedRows in class SimpleResults

Returns:

See above.

sessionClosing

public void sessionClosing()

Clears the backing results.

Specified by:

sessionClosing in interface Results

Overrides:

sessionClosing in class SimpleResults

cleanup

public void cleanup()

Clear the internal list of result rows and the backing results.

Specified by:

cleanup in interface Results

Overrides:

cleanup in class SimpleResults

isResultSetCached

public boolean isResultSetCached()

Indicate whether the full result set is cached in this object.

Specified by:

isResultSetCached in interface Results

Overrides:

isResultSetCached in class SimpleResults

Returns:

true if all results have been collected and cached, else false.

sessionEvent

public boolean sessionEvent(SessionListener.Event event)
                     throws PersistenceException

Invoked when a Hibernate session event occurs. This implementation is interested in receiving events related to the current transaction. In the case of a transaction about to commit, this method caches all remaining results (record IDs) into a SimpleResults instance. On rollback, it just cleans up.

Specified by:

sessionEvent in interface SessionListener

Parameters:

event - Session event type.

Returns:

true in this implemetation (i.e. this listener should be removed from the current set of registered listeners).

Throws:

PersistenceException - if any error occurs during the implementor's processing.

deregisteredSessionListener

public void deregisteredSessionListener()

No-op in this implementation.

Specified by:

deregisteredSessionListener in interface SessionListener

evaluate

public void evaluate(int row,
                     boolean firstOf)

Evalualte break row(s) which help to determine whether the given row if the first/last in a break group.

Specified by:

evaluate in interface Presorter.LazyEvaluator

Parameters:

row - Row to be checked as the beginning/end of a break group.

firstOf - true indicates that the row should be checked as the beginning of a break group. false indicates that the row should be checked as the end of a break group

cleanupBackingResults

private void cleanupBackingResults()

Clear the backing results.

loadRow

private void loadRow(int rowNumber)

Load the specified row into the cache.

Parameters:

rowNumber - Position of the requested row in the results set.

addRow

private void addRow(java.lang.Long[] ids)

Store the given record identifiers to the rows cache.

Parameters:

ids - Identifiers to be stored.

getRow

private java.lang.Long[] getRow(int row)

Get the specified row (an array of record identifiers).

Parameters:

row - Number of row to return.

Returns:

See above.

isFirst

private boolean isFirst(int row)

Tests whether the given row is the first row in the results set.

Parameters:

row - Row to test.

Returns:

true if the given row is the first row.

isLast

private boolean isLast(int row)

Tests whether the given row is the last row in the results set.

Parameters:

row - Row to test.

Returns:

true if the given row is the last row.

loadBDTIntoArray

private void loadBDTIntoArray(java.lang.Long[] ids,
                              BaseDataType[] targetArray)
                       throws PersistenceException

Load sort criteria values using identifiers of corresponding records.

Parameters:

ids - Array of record identifiers.

targetArray - Array for storing sort criteria values.

Throws:

PersistenceException - if there was an error creating a Hibernate session or getting a record or record eviction problems.