io.druid.query.aggregation

Interface BufferAggregator

All Known Implementing Classes:

ApproximateHistogramBufferAggregator, ApproximateHistogramFoldingBufferAggregator, CardinalityBufferAggregator, CountBufferAggregator, DoubleSumBufferAggregator, FilteredBufferAggregator, HistogramBufferAggregator, HyperUniquesBufferAggregator, JavaScriptBufferAggregator, LongSumBufferAggregator, MaxBufferAggregator, MinBufferAggregator

public interface BufferAggregator

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

Methods

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.
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.
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

Method Detail

init

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

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

close

void close()

Release any resources used by the aggregator