io.druid.query.aggregation

Interface BufferAggregator

All Superinterfaces:

HotLoopCallee

All Known Implementing Classes:

ApproximateHistogramBufferAggregator, ApproximateHistogramFoldingBufferAggregator, CardinalityBufferAggregator, CountBufferAggregator, DistinctCountBufferAggregator, DoubleFirstBufferAggregator, DoubleLastBufferAggregator, DoubleMaxBufferAggregator, DoubleMinBufferAggregator, DoublesSketchBuildBufferAggregator, DoublesSketchMergeBufferAggregator, DoublesSketchNoOpBufferAggregator, DoubleSumBufferAggregator, EmptyDistinctCountBufferAggregator, FilteredBufferAggregator, FloatFirstBufferAggregator, FloatLastBufferAggregator, FloatMaxBufferAggregator, FloatMinBufferAggregator, FloatSumBufferAggregator, HistogramBufferAggregator, HyperUniquesBufferAggregator, JavaScriptBufferAggregator, LongBufferAggregator, LongFirstBufferAggregator, LongLastBufferAggregator, LongMaxBufferAggregator, LongMinBufferAggregator, LongSumBufferAggregator, NoopBufferAggregator, SimpleDoubleBufferAggregator, SimpleFloatBufferAggregator, SketchBufferAggregator, TimestampBufferAggregator, VarianceBufferAggregator, VarianceBufferAggregator.FloatVarianceAggregator, VarianceBufferAggregator.LongVarianceAggregator, VarianceBufferAggregator.ObjectVarianceAggregator

public interface BufferAggregator
extends HotLoopCallee

A BufferAggregator is an object that can aggregate metrics into a ByteBuffer. Its aggregation-related methods (namely, aggregate(...) and get(...)) only take the ByteBuffer and position because it is assumed that the Aggregator was given something (one or more MetricSelector(s)) in its constructor that it can use to get at the next bit of data. Thus, an Aggregator can be thought of as a closure over some other thing that is stateful and changes between calls to aggregate(...).

Method Summary

Modifier and Type	Method and Description
void	aggregate(ByteBuffer buf, int position) Aggregates metric values into the given aggregate byte representation Implementations of this method must read in the aggregate value from the buffer at the given position, aggregate the next element of data and write the updated aggregate value back into the buffer.
void	close() Release any resources used by the aggregator
Object	get(ByteBuffer buf, int position) Returns the intermediate object representation of the given aggregate.
default double	getDouble(ByteBuffer buf, int position) Returns the double representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value.
float	getFloat(ByteBuffer buf, int position) Returns the float representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value.
long	getLong(ByteBuffer buf, int position) Returns the long representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value.
void	init(ByteBuffer buf, int position) Initializes the buffer location Implementations of this method must initialize the byte buffer at the given position Implementations must not change the position, limit or mark of the given buffer This method must not exceed the number of bytes returned by AggregatorFactory.getMaxIntermediateSize() in the corresponding AggregatorFactory
default void	inspectRuntimeShape(RuntimeShapeInspector inspector) Implementations of this method should call inspector.visit() with all fields of this class, which meet two conditions: 1.
default void	relocate(int oldPosition, int newPosition, ByteBuffer oldBuffer, ByteBuffer newBuffer) Relocates any cached objects.

Method Detail

init

@CalledFromHotLoop
void init(ByteBuffer buf,
                             int position)

Initializes the buffer location Implementations of this method must initialize the byte buffer at the given position Implementations must not change the position, limit or mark of the given buffer This method must not exceed the number of bytes returned by AggregatorFactory.getMaxIntermediateSize() in the corresponding AggregatorFactory

Parameters:

buf - byte buffer to initialize

position - offset within the byte buffer for initialization

aggregate

@CalledFromHotLoop
void aggregate(ByteBuffer buf,
                                  int position)

Aggregates metric values into the given aggregate byte representation Implementations of this method must read in the aggregate value from the buffer at the given position, aggregate the next element of data and write the updated aggregate value back into the buffer. Implementations must not change the position, limit or mark of the given buffer

Parameters:

buf - byte buffer storing the byte array representation of the aggregate

position - offset within the byte buffer at which the current aggregate value is stored

get

Object get(ByteBuffer buf,
           int position)

Returns the intermediate object representation of the given aggregate. Converts the given byte buffer representation into an intermediate aggregate Object Implementations must not change the position, limit or mark of the given buffer

Parameters:

buf - byte buffer storing the byte array representation of the aggregate

position - offset within the byte buffer at which the aggregate value is stored

Returns:

the Object representation of the aggregate

getFloat

float getFloat(ByteBuffer buf,
               int position)

Returns the float representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value. Implementations must not change the position, limit or mark of the given buffer Implementations are only required to support this method if they are aggregations which have an AggregatorFactory.getTypeName() of "float". If unimplemented, throwing an UnsupportedOperationException is common and recommended.

Parameters:

buf - byte buffer storing the byte array representation of the aggregate

position - offset within the byte buffer at which the aggregate value is stored

Returns:

the float representation of the aggregate

getLong

long getLong(ByteBuffer buf,
             int position)

Returns the long representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value. Implementations must not change the position, limit or mark of the given buffer Implementations are only required to support this method if they are aggregations which have an AggregatorFactory.getTypeName() of "long". If unimplemented, throwing an UnsupportedOperationException is common and recommended.

Parameters:

buf - byte buffer storing the byte array representation of the aggregate

position - offset within the byte buffer at which the aggregate value is stored

Returns:

the long representation of the aggregate

getDouble

default double getDouble(ByteBuffer buf,
                         int position)

Returns the double representation of the given aggregate byte array Converts the given byte buffer representation into the intermediate aggregate value. Implementations must not change the position, limit or mark of the given buffer Implementations are only required to support this method if they are aggregations which have an AggregatorFactory.getTypeName() of "double". If unimplemented, throwing an UnsupportedOperationException is common and recommended. The default implementation casts getFloat(ByteBuffer, int) to double. This default method is added to enable smooth backward compatibility, please re-implement it if your aggregators work with numeric double columns.

Parameters:

buf - byte buffer storing the byte array representation of the aggregate

position - offset within the byte buffer at which the aggregate value is stored

Returns:

the double representation of the aggregate

close

void close()

Release any resources used by the aggregator

inspectRuntimeShape

default void inspectRuntimeShape(RuntimeShapeInspector inspector)

Implementations of this method should call inspector.visit() with all fields of this class, which meet two conditions: 1. They are used in methods of this class, annotated with CalledFromHotLoop 2. They are either: a. Nullable objects b. Instances of HotLoopCallee c. Objects, which don't always have a specific class in runtime. For example, a field of type Set could be HashSet or TreeSet in runtime, depending on how this instance (the instance on which inspectRuntimeShape() is called) is configured. d. ByteBuffer or similar objects, where byte order matters e. boolean flags, affecting branch taking f. Arrays of objects, meeting any of conditions a-e.

The default implementation inspects nothing. Classes that implement BufferAggregator are encouraged to override this method, following the specification of HotLoopCallee.inspectRuntimeShape(io.druid.query.monomorphicprocessing.RuntimeShapeInspector).

Specified by:

inspectRuntimeShape in interface HotLoopCallee

relocate

default void relocate(int oldPosition,
                      int newPosition,
                      ByteBuffer oldBuffer,
                      ByteBuffer newBuffer)

Relocates any cached objects. If underlying ByteBuffer used for aggregation buffer relocates to a new ByteBuffer, positional caches(if any) built on top of old ByteBuffer can not be used for further aggregate(ByteBuffer, int) calls. This method tells the BufferAggregator that the cached objects at a certain location has been relocated to a different location. Only used if there is any positional caches/objects in the BufferAggregator implementation. If relocate happens to be across multiple new ByteBuffers (say n ByteBuffers), this method should be called multiple times(n times) given all the new positions/old positions should exist in newBuffer/OldBuffer. Implementations must not change the position, limit or mark of the given buffer

Parameters:

oldPosition - old position of a cached object before aggregation buffer relocates to a new ByteBuffer.

newPosition - new position of a cached object after aggregation buffer relocates to a new ByteBuffer.

oldBuffer - old aggregation buffer.

newBuffer - new aggregation buffer.