com.bigdata.bop.ap

Class SampleIndex.SmartOffsetSampler

java.lang.Object

com.bigdata.bop.ap.SampleIndex.SmartOffsetSampler

All Implemented Interfaces:

SampleIndex.IOffsetSampler

Enclosing class:

SampleIndex<E>

public static class SampleIndex.SmartOffsetSampler
extends Object
implements SampleIndex.IOffsetSampler

A smart implementation which uses whichever implementation is most efficient for the limit and key range to be sampled.

Author:

thompsonbry

Constructor Summary

Constructors

Constructor and Description
SampleIndex.SmartOffsetSampler()

Method Summary

Methods

Modifier and Type	Method and Description
long[]	getOffsets(long seed, int limit, long fromIndex, long toIndex) Return an array of tuple indices which may be used to sample a key range of some index.

Methods inherited from class java.lang.Object

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

Constructor Detail

SampleIndex.SmartOffsetSampler

public SampleIndex.SmartOffsetSampler()

Method Detail

getOffsets

public long[] getOffsets(long seed,
                int limit,
                long fromIndex,
                long toIndex)

Return an array of tuple indices which may be used to sample a key range of some index.

Note: The caller must stop when it runs out of offsets, not when the limit is satisfied, as there will be fewer offsets returned when the half open range is smaller than the limit.

Specified by:

getOffsets in interface SampleIndex.IOffsetSampler

Parameters:

seed - The seed for the random number generator -or- ZERO (0L) for a random seed. A non-zero value may be used to create a repeatable sample.

limit - The maximum #of tuples to sample.

fromIndex - The inclusive lower bound.

toIndex - The exclusive upper bound0

Returns:

An array of at most limit offsets into the index. The offsets will lie in the half open range (fromIndex,toIndex]. The elements of the array will be in ascending order. No offsets will be repeated.