Package org.apache.druid.segment

Class ForwardingRowIterator

java.lang.Object

org.apache.druid.segment.ForwardingRowIterator

All Implemented Interfaces:

Closeable, AutoCloseable, RowIterator, TimeAndDimsIterator, TransformableRowIterator

public abstract class ForwardingRowIterator
extends Object
implements TransformableRowIterator

Implementation of TransformableRowIterator that just delegates all methods to some baseIterator (adapter pattern). Subclass should override some methods.

Field Summary

Fields

Modifier and Type	Field	Description
protected final TransformableRowIterator	baseIterator

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ForwardingRowIterator(TransformableRowIterator baseIterator)

Method Summary

Modifier and Type	Method	Description
void	close()	Closes any resources, associated with this iterator.
TimeAndDimsPointer	getMarkedPointer()	Returns a pointer to the row, that was the current row when RowIterator.mark() was called for the last time.
RowPointer	getPointer()	Returns a pointer to the current row.
boolean	hasTimeAndDimsChangedSinceMark()	Compares the "memoized" data point from the last RowIterator.mark() call with the data point, to which RowIterator.getPointer() currently points.
void	mark()	"Memoizes" the data point, to which RowIterator.getPointer() currently points.
boolean	moveToNext()	Moves iterator to the next data point.

Methods inherited from class java.lang.Object

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

Field Details

baseIterator

protected final TransformableRowIterator baseIterator

Constructor Details

ForwardingRowIterator

protected ForwardingRowIterator(TransformableRowIterator baseIterator)

Method Details

mark

public void mark()

Description copied from interface: RowIterator

"Memoizes" the data point, to which RowIterator.getPointer() currently points. If the last call to TimeAndDimsIterator.moveToNext() returned false, the behaviour of this method is undefined, e. g. it may throw a runtime exception.

Specified by:

mark in interface RowIterator

getMarkedPointer

public TimeAndDimsPointer getMarkedPointer()

Description copied from interface: TransformableRowIterator

Returns a pointer to the row, that was the current row when RowIterator.mark() was called for the last time. This method always returns the same object, but pointing to different rows after each RowIterator.mark() call. This method must not be called before ever calling to TimeAndDimsIterator.moveToNext(). If the very first call to TimeAndDimsIterator.moveToNext() returned false, the behaviour of this method is undefined (it may return a "wrong" pointer, null, throw an exception, etc.). This method could be called before the first call to RowIterator.mark() (it should return the same object as it is required to return after all subsequent RowIterator.mark() calls), but the data of the returned pointer should not be accessed before the first call to RowIterator.mark(). This method is used in RowCombiningTimeAndDimsIterator implementation. getMarkedPointer() returns TimeAndDimsPointer instead of RowPointer (like TransformableRowIterator.getPointer()) merely because RowCombiningTimeAndDimsIterator doesn't need this method to return anything more specific than TimeAndDimsPointer.

Specified by:

getMarkedPointer in interface TransformableRowIterator

hasTimeAndDimsChangedSinceMark

public boolean hasTimeAndDimsChangedSinceMark()

Description copied from interface: RowIterator

Compares the "memoized" data point from the last RowIterator.mark() call with the data point, to which RowIterator.getPointer() currently points. Comparison is made in terms of TimeAndDimsPointer.compareTo(org.apache.druid.segment.TimeAndDimsPointer) contract. If RowIterator.mark() has never been called, or the last call to TimeAndDimsIterator.moveToNext() returned false, the behaviour of this method is undefined: it may arbitrarily return true, or false, or throw a runtime exception.

Specified by:

hasTimeAndDimsChangedSinceMark in interface RowIterator

getPointer

public RowPointer getPointer()

Description copied from interface: TransformableRowIterator

Returns a pointer to the current row. This method _always returns the same object_, but pointing to different row after each TimeAndDimsIterator.moveToNext() call that returns {@link true}. Other aspects of the behaviour of this method are the same as in the generic RowIterator.getPointer() contract.

Specified by:

getPointer in interface RowIterator

Specified by:

getPointer in interface TimeAndDimsIterator

Specified by:

getPointer in interface TransformableRowIterator

moveToNext

public boolean moveToNext()

Description copied from interface: TimeAndDimsIterator

Moves iterator to the next data point. This method must be called before the first use of TimeAndDimsIterator.getPointer(). As long as this method returns true, TimeAndDimsIterator.getPointer() could be safely called; after this method returned false, this iterator is done, TimeAndDimsIterator.getPointer() must _not_ be called, and TimeAndDimsIterator.close() should be called.

Specified by:

moveToNext in interface TimeAndDimsIterator

close

public void close()

Description copied from interface: TimeAndDimsIterator

Closes any resources, associated with this iterator.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface TimeAndDimsIterator