Package org.apache.druid.segment

Interface TransformableRowIterator

All Superinterfaces:

AutoCloseable, Closeable, RowIterator, TimeAndDimsIterator

All Known Implementing Classes:

ForwardingRowIterator

public interface TransformableRowIterator
extends RowIterator

TransformableRowIterator tightens RowIterator.getPointer() contract, that allows to transform iterated rows without allocations on each iterations, and reuse the mechanics of the underlying iterator. See IndexMerger.toMergedIndexRowIterator(org.apache.druid.segment.TransformableRowIterator, int, java.util.List<org.apache.druid.segment.DimensionMergerV9>) for an example.

Method Summary

Modifier and Type	Method	Description
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.

Methods inherited from interface org.apache.druid.segment.RowIterator

hasTimeAndDimsChangedSinceMark, mark

Methods inherited from interface org.apache.druid.segment.TimeAndDimsIterator

close, moveToNext

Method Detail

getPointer

RowPointer getPointer()

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

getMarkedPointer

TimeAndDimsPointer getMarkedPointer()

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 getPointer()) merely because RowCombiningTimeAndDimsIterator doesn't need this method to return anything more specific than TimeAndDimsPointer.