Package org.apache.druid.segment

Class UnnestDimensionCursor

java.lang.Object

org.apache.druid.segment.UnnestDimensionCursor

All Implemented Interfaces:

Cursor

public class UnnestDimensionCursor
extends Object
implements Cursor

The cursor to help unnest MVDs with dictionary encoding. Consider a segment has 2 rows ['a', 'b', 'c'] ['d', 'c']

Considering dictionary encoding, these are represented as

'a' -> 0 'b' -> 1 'c' -> 2 'd' -> 3

The baseCursor points to the row of IndexedInts [0, 1, 2] while the unnestCursor with each call of advance() moves over individual elements.

advance() -> 0 -> 'a' advance() -> 1 -> 'b' advance() -> 2 -> 'c' advance() -> 3 -> 'd' (advances base cursor first) advance() -> 2 -> 'c'

Total 5 advance calls above

The index reference points to the index of each row that the unnest cursor is accessing The indexedInts for each row are held in the indexedIntsForCurrentRow object

The needInitialization flag sets up the initial values of indexedIntsForCurrentRow at the beginning of the segment

Constructor Summary

Constructors

Constructor	Description
UnnestDimensionCursor(Cursor cursor, ColumnSelectorFactory baseColumnSelectorFactory, VirtualColumn unnestColumn)

Method Summary

Modifier and Type	Method	Description
void	advance()	Advance the cursor to the next position, checking if thread has been interrupted after advancing and possibly throwing QueryInterruptedException if so.
void	advanceUninterruptibly()	Advance to the cursor to the next position.
ColumnSelectorFactory	getColumnSelectorFactory()	Get a ColumnSelectorFactory whose selectors will be backed by the row values at the current position of the cursor
boolean	isDone()	Check if the current cursor position is valid, returning false if there are values to read from selectors created by Cursor.getColumnSelectorFactory().
boolean	isDoneOrInterrupted()	Check if the current cursor position is valid, or if the thread has been interrupted.
void	reset()	Reset to start of cursor.

Methods inherited from class java.lang.Object

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

Constructor Details

UnnestDimensionCursor

public UnnestDimensionCursor(Cursor cursor,
 ColumnSelectorFactory baseColumnSelectorFactory,
 VirtualColumn unnestColumn)

Method Details

getColumnSelectorFactory

public ColumnSelectorFactory getColumnSelectorFactory()

Description copied from interface: Cursor

Get a ColumnSelectorFactory whose selectors will be backed by the row values at the current position of the cursor

Specified by:

getColumnSelectorFactory in interface Cursor

advance

public void advance()

Description copied from interface: Cursor

Advance the cursor to the next position, checking if thread has been interrupted after advancing and possibly throwing QueryInterruptedException if so. Callers should check Cursor.isDone() or Cursor.isDoneOrInterrupted() before getting the next value from a selector.

Specified by:

advance in interface Cursor

advanceUninterruptibly

public void advanceUninterruptibly()

Description copied from interface: Cursor

Advance to the cursor to the next position. Callers should check Cursor.isDone() or Cursor.isDoneOrInterrupted() before getting the next value from a selector. However, underlying implementation may still check for thread interruption if advancing the cursor is a long-running operation.

Specified by:

advanceUninterruptibly in interface Cursor

isDone

public boolean isDone()

Description copied from interface: Cursor

Check if the current cursor position is valid, returning false if there are values to read from selectors created by Cursor.getColumnSelectorFactory(). If true, any such selectors will no longer produce values.

Specified by:

isDone in interface Cursor

isDoneOrInterrupted

public boolean isDoneOrInterrupted()

Description copied from interface: Cursor

Check if the current cursor position is valid, or if the thread has been interrupted.

Specified by:

isDoneOrInterrupted in interface Cursor

See Also:

• Cursor.isDone()

reset

public void reset()

Description copied from interface: Cursor

Reset to start of cursor. Most cursor implementations are backed by immutable data, but there is generically no guarantee that advancing through a cursor again will read exactly the same data or even number of rows, since the underlying data might be mutable in some cases.

Specified by:

reset in interface Cursor