Package org.apache.druid.query.groupby.epinephelinae.column

Class DictionaryBuildingGroupByColumnSelectorStrategy<DimensionType>

java.lang.Object

org.apache.druid.query.groupby.epinephelinae.column.DictionaryBuildingGroupByColumnSelectorStrategy<DimensionType>

All Implemented Interfaces:

ColumnSelectorStrategy, GroupByColumnSelectorStrategy

@NotThreadSafe
public class DictionaryBuildingGroupByColumnSelectorStrategy<DimensionType>
extends Object

Strategy for grouping dimensions which can have variable-width objects, and aren't backed by prebuilt dictionaries. It encapsulates the dictionary building logic, along with providing the implementations for dimension to dictionary id encoding-decoding.

This strategy can handle any dimension that can be addressed on a reverse-dictionary. Reverse dictionary uses a sorted map, rather than a hashmap.

This is the most expensive of all the strategies, and hence must be used only when other strategies aren't valid.

Field Summary

Fields inherited from interface org.apache.druid.query.groupby.epinephelinae.column.GroupByColumnSelectorStrategy

GROUP_BY_MISSING_VALUE

Method Summary

Modifier and Type	Method	Description
Grouper.BufferComparator	bufferComparator(int keyBufferPosition, StringComparator stringComparator)	Return BufferComparator for values written using this strategy when limit is pushed down to segment scan.
boolean	checkRowIndexAndAddValueToGroupingKey(int keyBufferPosition, Object rowObj, int rowValIdx, ByteBuffer keyBuffer)	If rowValIdx is less than the size of rowObj (haven't handled all of the row values): First, read the value at rowValIdx from a rowObj and write that value to the keyBuffer at keyBufferPosition.
static GroupByColumnSelectorStrategy	forType(ColumnType columnType)	Creates an implementation of the strategy for the given type
int	getGroupingKeySizeBytes()	Strategy maps to integer dictionary ids
int	initColumnValues(ColumnValueSelector selector, int columnIndex, Object[] valuess)	Retrieve a row object from the ColumnValueSelector and put it in valuess at columnIndex.
void	initGroupingKeyColumnValue(int keyBufferPosition, int dimensionIndex, Object rowObj, ByteBuffer keyBuffer, int[] stack)	Read the first value within a row values object (e.
void	processValueFromGroupingKey(GroupByColumnSelectorPlus selectorPlus, ByteBuffer key, ResultRow resultRow, int keyBufferPosition)	Read a value from a grouping key and add it to the group by query result row, using the output name specified in a DimensionSpec.
void	reset()	Reset any internal state held by this selector.
int	writeToKeyBuffer(int keyBufferPosition, ColumnValueSelector selector, ByteBuffer keyBuffer)	Write a single object from the given selector to the keyBuffer at keyBufferPosition.

Methods inherited from class java.lang.Object

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

Method Details

forType

public static GroupByColumnSelectorStrategy forType(ColumnType columnType)

Creates an implementation of the strategy for the given type

getGroupingKeySizeBytes

public int getGroupingKeySizeBytes()

Strategy maps to integer dictionary ids

Specified by:

getGroupingKeySizeBytes in interface GroupByColumnSelectorStrategy

Returns:

size, in bytes, of this dimension's values in the grouping key.

processValueFromGroupingKey

public void processValueFromGroupingKey(GroupByColumnSelectorPlus selectorPlus,
 ByteBuffer key,
 ResultRow resultRow,
 int keyBufferPosition)

Description copied from interface: GroupByColumnSelectorStrategy

Read a value from a grouping key and add it to the group by query result row, using the output name specified in a DimensionSpec. An implementation may choose to not add anything to the result row (e.g., as the String implementation does for empty rows) selectorPlus provides access to: - the keyBufferPosition offset from which to read the value - the dimension value selector - the DimensionSpec for this dimension from the query

Specified by:

processValueFromGroupingKey in interface GroupByColumnSelectorStrategy

Parameters:

selectorPlus - dimension info containing the key offset, value selector, and dimension spec

key - grouping key

resultRow - result row for the group by query being served

keyBufferPosition - buffer position for the grouping key, added to support chaining multiple ColumnSelectorStrategy

initColumnValues

public int initColumnValues(ColumnValueSelector selector,
 int columnIndex,
 Object[] valuess)

Description copied from interface: GroupByColumnSelectorStrategy

Retrieve a row object from the ColumnValueSelector and put it in valuess at columnIndex.

Specified by:

initColumnValues in interface GroupByColumnSelectorStrategy

Parameters:

selector - Value selector for a column.

columnIndex - Index of the column within the row values array

valuess - Row values array, one index per column

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.

initGroupingKeyColumnValue

public void initGroupingKeyColumnValue(int keyBufferPosition,
 int dimensionIndex,
 Object rowObj,
 ByteBuffer keyBuffer,
 int[] stack)

Description copied from interface: GroupByColumnSelectorStrategy

Read the first value within a row values object (e. g. IndexedInts, as the value in a dictionary-encoded string column) and write that value to the keyBuffer at keyBufferPosition. If the row size is 0 (e. g. IndexedInts.size()), write GroupByColumnSelectorStrategy.GROUP_BY_MISSING_VALUE instead. If the size of the row is > 0, write 1 to stack[] at columnIndex, otherwise write 0.

Specified by:

initGroupingKeyColumnValue in interface GroupByColumnSelectorStrategy

Parameters:

keyBufferPosition - Starting offset for this column's value within the grouping key.

dimensionIndex - Index of this dimension within the stack array

rowObj - Row value object for this column

keyBuffer - grouping key

stack - array containing the current within-row value index for each column

checkRowIndexAndAddValueToGroupingKey

public boolean checkRowIndexAndAddValueToGroupingKey(int keyBufferPosition,
 Object rowObj,
 int rowValIdx,
 ByteBuffer keyBuffer)

Description copied from interface: GroupByColumnSelectorStrategy

If rowValIdx is less than the size of rowObj (haven't handled all of the row values): First, read the value at rowValIdx from a rowObj and write that value to the keyBuffer at keyBufferPosition. Then return true. This method assumes that the size increase associated with the dictionary building has occurred already when calling GroupByColumnSelectorStrategy.initColumnValues(org.apache.druid.segment.ColumnValueSelector, int, java.lang.Object[]) Otherwise, return false.

Specified by:

checkRowIndexAndAddValueToGroupingKey in interface GroupByColumnSelectorStrategy

Parameters:

keyBufferPosition - Starting offset for this column's value within the grouping key.

rowObj - Row value object for this column (e.g., IndexedInts)

rowValIdx - Index of the current value being grouped on within the row

keyBuffer - grouping key

Returns:

true if rowValIdx invalid input: '<' size of rowObj, false otherwise

writeToKeyBuffer

public int writeToKeyBuffer(int keyBufferPosition,
 ColumnValueSelector selector,
 ByteBuffer keyBuffer)

Description copied from interface: GroupByColumnSelectorStrategy

Write a single object from the given selector to the keyBuffer at keyBufferPosition. The reading column must have a single value. The position of the keyBuffer may be modified.

Specified by:

writeToKeyBuffer in interface GroupByColumnSelectorStrategy

Parameters:

keyBufferPosition - starting offset for this column's value within the grouping key

selector - selector to retrieve row value object from

keyBuffer - grouping key

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.

bufferComparator

public Grouper.BufferComparator bufferComparator(int keyBufferPosition,
 @Nullable
 StringComparator stringComparator)

Description copied from interface: GroupByColumnSelectorStrategy

Return BufferComparator for values written using this strategy when limit is pushed down to segment scan.

Specified by:

bufferComparator in interface GroupByColumnSelectorStrategy

Parameters:

keyBufferPosition - starting offset for this column's value within the grouping key

stringComparator - stringComparator from LimitSpec for this column. If this is null, implementations will use the StringComparators.LEXICOGRAPHIC comparator.

Returns:

BufferComparator for comparing values written

reset

public void reset()

Description copied from interface: GroupByColumnSelectorStrategy

Reset any internal state held by this selector. After this method is called, any row objects or key objects generated by any methods of this class must be considered unreadable. Calling GroupByColumnSelectorStrategy.processValueFromGroupingKey(org.apache.druid.query.groupby.epinephelinae.column.GroupByColumnSelectorPlus, java.nio.ByteBuffer, org.apache.druid.query.groupby.ResultRow, int) on that memory has undefined behavior.

Specified by:

reset in interface GroupByColumnSelectorStrategy