Package org.apache.druid.segment.join

Class PostJoinCursor

java.lang.Object

org.apache.druid.segment.join.PostJoinCursor

All Implemented Interfaces:

Cursor

public class PostJoinCursor
extends Object
implements Cursor

A Cursor decorator used by HashJoinSegmentCursorFactory.makeCursorHolder(CursorBuildSpec) to add post-join virtual columns and filters.

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()	Advancing the post-join requires evaluating the join on whole segment and advancing without interruption can take a long time if there are no matches but the join itself is big.
ColumnSelectorFactory	getColumnSelectorFactory()	Get a ColumnSelectorFactory whose selectors will be backed by the row values at the current position of the cursor
Filter	getPostJoinFilter()
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.
void	setValueMatcher(ValueMatcher valueMatcher)
static PostJoinCursor	wrap(Cursor baseCursor, VirtualColumns virtualColumns, Filter filter)

Methods inherited from class java.lang.Object

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

Method Details

wrap

public static PostJoinCursor wrap(Cursor baseCursor,
 VirtualColumns virtualColumns,
 @Nullable
 Filter filter)

setValueMatcher

public void setValueMatcher(@Nullable
 ValueMatcher valueMatcher)

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

getPostJoinFilter

@Nullable
public Filter getPostJoinFilter()

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()

Advancing the post-join requires evaluating the join on whole segment and advancing without interruption can take a long time if there are no matches but the join itself is big. This can leave the thread running well after the timeout elapses. One such issue is described in CPU thread running PostJoinCursor cannot be terminated

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