com.bigdata.bop.ap

Interface SampleIndex.IOffsetSampler

All Known Implementing Classes:

SampleIndex.AcceptanceSetOffsetSampler, SampleIndex.BitVectorOffsetSampler, SampleIndex.EntireRangeOffsetSampler, SampleIndex.SmartOffsetSampler

Enclosing class:

SampleIndex<E>

public static interface SampleIndex.IOffsetSampler

Interface for obtaining an array of tuple offsets to be sampled.

Author:

thompsonbry

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.

Method Detail

getOffsets

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.

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.

Throws:

IllegalArgumentException - if limit is non-positive.

IllegalArgumentException - if fromIndex is negative.

IllegalArgumentException - if toIndex is negative.

IllegalArgumentException - unless toIndex is GT fromIndex.