Package org.apache.druid.segment.virtual

Class ExpressionDeferredGroupByVectorColumnSelector

java.lang.Object

org.apache.druid.segment.virtual.ExpressionDeferredGroupByVectorColumnSelector

All Implemented Interfaces:

GroupingSelector, GroupByVectorColumnSelector

public class ExpressionDeferredGroupByVectorColumnSelector
extends Object
implements GroupByVectorColumnSelector

Implementation of GroupByVectorColumnSelector that uses a wide key representing all expression inputs to enable deferring expression evaluation to writeKeyToResultRow(MemoryPointer, int, ResultRow, int). For example, the expression "coalesce(x, y)" would write a key composed of (x, y) in writeKeys(org.apache.datasketches.memory.WritableMemory, int, int, int, int), then compute "coalesce(x, y)" in writeKeyToResultRow(org.apache.druid.query.groupby.epinephelinae.collection.MemoryPointer, int, org.apache.druid.query.groupby.ResultRow, int).

Method Summary

Modifier and Type	Method	Description
int	getGroupingKeySize()	Get the size in bytes of the key parts generated by this column.
int	getValueCardinality()	Returns the value cardinality if it is known (such as when backed by a DimensionDictionarySelector).
void	reset()	Reset any internal state held by this selector.
int	writeKeys(org.apache.datasketches.memory.WritableMemory keySpace, int keySize, int keyOffset, int startRow, int endRow)	Write key parts for this column, from startRow (inclusive) to endRow (exclusive), into keySpace starting at keyOffset.
void	writeKeyToResultRow(MemoryPointer keyMemory, int keyOffset, ResultRow resultRow, int resultRowPosition)	Write key parts for this column into a particular result row.

Methods inherited from class java.lang.Object

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

Method Detail

getGroupingKeySize

public int getGroupingKeySize()

Description copied from interface: GroupByVectorColumnSelector

Get the size in bytes of the key parts generated by this column.

Specified by:

getGroupingKeySize in interface GroupByVectorColumnSelector

getValueCardinality

public int getValueCardinality()

Description copied from interface: GroupingSelector

Returns the value cardinality if it is known (such as when backed by a DimensionDictionarySelector). If there are only null values, this method should return 1. If the cardinality is not known, returns DimensionDictionarySelector.CARDINALITY_UNKNOWN.

Specified by:

getValueCardinality in interface GroupingSelector

writeKeys

public int writeKeys(org.apache.datasketches.memory.WritableMemory keySpace,
                     int keySize,
                     int keyOffset,
                     int startRow,
                     int endRow)

Description copied from interface: GroupByVectorColumnSelector

Write key parts for this column, from startRow (inclusive) to endRow (exclusive), into keySpace starting at keyOffset.

Specified by:

writeKeys in interface GroupByVectorColumnSelector

Parameters:

keySpace - key memory

keySize - size of the overall key (not just the part for this column)

keyOffset - starting position for the first key part within keySpace

startRow - starting row (inclusive) within the current vector

endRow - ending row (exclusive) within the current vector

Returns:

estimated increase in internal state footprint, in bytes, as a result of this operation. May be zero if memory did not increase as a result of this operation. Will not be negative.

writeKeyToResultRow

public void writeKeyToResultRow(MemoryPointer keyMemory,
                                int keyOffset,
                                ResultRow resultRow,
                                int resultRowPosition)

Description copied from interface: GroupByVectorColumnSelector

Write key parts for this column into a particular result row.

Specified by:

writeKeyToResultRow in interface GroupByVectorColumnSelector

Parameters:

keyMemory - key memory

keyOffset - starting position for this key part within keyMemory (starting from MemoryPointer.position)

resultRow - result row to receive key parts

resultRowPosition - position within the result row for this key part

reset

public void reset()

Description copied from interface: GroupByVectorColumnSelector

Reset any internal state held by this selector. After this method is called, any memory previously written by GroupByVectorColumnSelector.writeKeys(org.apache.datasketches.memory.WritableMemory, int, int, int, int) must be considered unreadable. Calling GroupByVectorColumnSelector.writeKeyToResultRow(org.apache.druid.query.groupby.epinephelinae.collection.MemoryPointer, int, org.apache.druid.query.groupby.ResultRow, int) on that memory has undefined behavior.

Specified by:

reset in interface GroupByVectorColumnSelector