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

Class BufferArrayGrouper

java.lang.Object

org.apache.druid.query.groupby.epinephelinae.BufferArrayGrouper

All Implemented Interfaces:

Closeable, AutoCloseable, Grouper<IntKey>, IntGrouper, VectorGrouper

public class BufferArrayGrouper
extends Object
implements VectorGrouper, 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 org.apache.druid.query.groupby.epinephelinae.Grouper

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

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

IntGrouper.IntGrouperHashFunction

Constructor Summary

Constructors

Constructor	Description
BufferArrayGrouper(com.google.common.base.Supplier<ByteBuffer> bufferSupplier, AggregatorAdapters aggregators, int cardinality)

Method Summary

Modifier and Type	Method	Description
AggregateResult	aggregateKeyHash(int dimIndex)
AggregateResult	aggregateVector(org.apache.datasketches.memory.Memory keySpace, int startRow, int endRow)	Aggregate the current vector of rows from "startRow" to "endRow" using the provided keys.
void	close()	Close the grouper and release associated resources.
IntGrouper.IntGrouperHashFunction	hashFunction()
void	init()	Initialize the grouper.
void	initVectorized(int maxVectorSize)	Initialize the grouper.
boolean	isInitialized()	Check this grouper is initialized or not.
CloseableIterator<Grouper.Entry<MemoryPointer>>	iterator()	Iterate through entry buckets.
CloseableIterator<Grouper.Entry<IntKey>>	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 org.apache.druid.query.groupby.epinephelinae.IntGrouper

aggregate, aggregate, aggregate

Constructor Detail

BufferArrayGrouper

public BufferArrayGrouper(com.google.common.base.Supplier<ByteBuffer> bufferSupplier,
                          AggregatorAdapters aggregators,
                          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<IntKey>

initVectorized

public void initVectorized(int maxVectorSize)

Description copied from interface: VectorGrouper

Initialize the grouper. This method needs to be called before calling VectorGrouper.aggregateVector(org.apache.datasketches.memory.Memory, int, int).

Specified by:

initVectorized in interface VectorGrouper

isInitialized

public boolean isInitialized()

Description copied from interface: Grouper

Check this grouper is initialized or not.

Specified by:

isInitialized in interface Grouper<IntKey>

Returns:

true if the grouper is already initialized, otherwise false.

aggregateKeyHash

public AggregateResult aggregateKeyHash(int dimIndex)

Specified by:

aggregateKeyHash in interface IntGrouper

aggregateVector

public AggregateResult aggregateVector(org.apache.datasketches.memory.Memory keySpace,
                                       int startRow,
                                       int endRow)

Description copied from interface: VectorGrouper

Aggregate the current vector of rows from "startRow" to "endRow" using the provided keys.

Specified by:

aggregateVector in interface VectorGrouper

Parameters:

keySpace - array holding keys, chunked into ints. First (endRow - startRow) keys must be valid.

startRow - row to start at (inclusive).

endRow - row to end at (exclusive).

Returns:

result that indicates how many keys were aggregated (may be partial due to resource limits)

reset

public void reset()

Description copied from interface: VectorGrouper

Reset the grouper to its initial state.

Specified by:

reset in interface Grouper<IntKey>

Specified by:

reset in interface VectorGrouper

hashFunction

public IntGrouper.IntGrouperHashFunction hashFunction()

Specified by:

hashFunction in interface Grouper<IntKey>

Specified by:

hashFunction in interface IntGrouper

close

public void close()

Description copied from interface: VectorGrouper

Close the grouper and release associated resources.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface Grouper<IntKey>

Specified by:

close in interface VectorGrouper

iterator

public CloseableIterator<Grouper.Entry<MemoryPointer>> iterator()

Description copied from interface: VectorGrouper

Iterate through entry buckets. Each bucket's key is a MemoryPointer object in native byte order.

After you are done with the iterator returned by this method, you should either call VectorGrouper.close() (if you are done with the VectorGrouper) or VectorGrouper.reset() (if you want to reuse it).

Callers must process and discard the returned Grouper.Entrys immediately, because objects may be reused.

Specified by:

iterator in interface VectorGrouper

Returns:

entry iterator

iterator

public CloseableIterator<Grouper.Entry<IntKey>> iterator(boolean sorted)

Description copied from interface: Grouper

Iterate through entries.

Some implementations allow writes even after this method is called. After you are done with the iterator returned by this method, you should either call Grouper.close() (if you are done with the Grouper) or Grouper.reset() (if you want to reuse it). Some implementations allow calling Grouper.iterator(boolean) again if you want another iterator. But, this method 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 Grouper.KeySerde.bufferComparator() 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<IntKey>

Parameters:

sorted - return sorted results

Returns:

entry iterator