io.druid.query.groupby.epinephelinae

Class BufferArrayGrouper

java.lang.Object

io.druid.query.groupby.epinephelinae.BufferArrayGrouper

All Implemented Interfaces:

Grouper<Integer>, IntGrouper, Closeable, AutoCloseable

public class BufferArrayGrouper
extends Object
implements IntGrouper

A buffer grouper for array-based aggregation. This grouper stores aggregated values in the buffer using the grouping key as the index.

The buffer is divided into 2 separate regions, i.e., used flag buffer and value buffer. The used flag buffer is a bit set to represent which keys are valid. If a bit of an index is set, that key is valid. Finally, the value buffer is used to store aggregated values. The first index is reserved for GroupByColumnSelectorStrategy.GROUP_BY_MISSING_VALUE.

This grouper is available only when the grouping key is a single indexed dimension of a known cardinality because it directly uses the dimension value as the index for array access. Since the cardinality for the grouping key across different segments cannot be currently retrieved, this grouper can be used only when performing per-segment query execution.

Nested Class Summary

Nested classes/interfaces inherited from interface io.druid.query.groupby.epinephelinae.IntGrouper

IntGrouper.IntGrouperHashFunction

Nested classes/interfaces inherited from interface io.druid.query.groupby.epinephelinae.Grouper

Grouper.BufferComparator, Grouper.Entry<T>, Grouper.KeySerde<T>, Grouper.KeySerdeFactory<T>

Constructor Summary

Constructors

Constructor and Description
BufferArrayGrouper(com.google.common.base.Supplier<ByteBuffer> bufferSupplier, ColumnSelectorFactory columnSelectorFactory, AggregatorFactory[] aggregatorFactories, int cardinality)

Method Summary

Modifier and Type	Method and Description
AggregateResult	aggregate(int key, int dimIndex)
void	close() Close the grouper and release associated resources.
IntGrouper.IntGrouperHashFunction	hashFunction()
void	init() Initialize the grouper.
boolean	isInitialized() Check this grouper is initialized or not.
Iterator<Grouper.Entry<Integer>>	iterator(boolean sorted) Iterate through entries.
void	reset() Reset the grouper to its initial state.

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.druid.query.groupby.epinephelinae.IntGrouper

aggregate, aggregate, aggregate

Constructor Detail

BufferArrayGrouper

public BufferArrayGrouper(com.google.common.base.Supplier<ByteBuffer> bufferSupplier,
                          ColumnSelectorFactory columnSelectorFactory,
                          AggregatorFactory[] aggregatorFactories,
                          int cardinality)

Method Detail

init

public void init()

Description copied from interface: Grouper

Initialize the grouper. This method needs to be called before calling Grouper.aggregate(Object) and Grouper.aggregate(Object, int).

Specified by:

init in interface Grouper<Integer>

isInitialized

public boolean isInitialized()

Description copied from interface: Grouper

Check this grouper is initialized or not.

Specified by:

isInitialized in interface Grouper<Integer>

Returns:

true if the grouper is already initialized, otherwise false.

aggregate

public AggregateResult aggregate(int key,
                                 int dimIndex)

Specified by:

aggregate in interface IntGrouper

reset

public void reset()

Description copied from interface: Grouper

Reset the grouper to its initial state.

Specified by:

reset in interface Grouper<Integer>

hashFunction

public IntGrouper.IntGrouperHashFunction hashFunction()

Specified by:

hashFunction in interface Grouper<Integer>

Specified by:

hashFunction in interface IntGrouper

close

public void close()

Description copied from interface: Grouper

Close the grouper and release associated resources.

Specified by:

close in interface Grouper<Integer>

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

iterator

public Iterator<Grouper.Entry<Integer>> iterator(boolean sorted)

Description copied from interface: Grouper

Iterate through entries.

Once this method is called, writes are no longer safe. After you are done with the iterator returned by this method, you should either call Grouper.close() (if you are done with the Grouper), Grouper.reset() (if you want to reuse it), or Grouper.iterator(boolean) again if you want another iterator. This method is not thread-safe and must not be called by multiple threads concurrently.

If "sorted" is true then the iterator will return sorted results. It will use KeyType's natural ordering on deserialized objects, and will use the KeySerde#comparator() on serialized objects. Woe be unto you if these comparators are not equivalent.

Callers must process and discard the returned Grouper.Entrys immediately because some implementations can reuse the key objects.

Specified by:

iterator in interface Grouper<Integer>

Parameters:

sorted - return sorted results

Returns:

entry iterator