class BruteForceSampling(BaseSampling):
"""Heuristic sampling using raw % size for sample size and :class:`Bernoulli <snowshu.samplings.sample_methods.bernoulli_sample_method.BernoulliSampleMethod>` sampling.
Args:
probability: The % sample size desired in decimal format from 0.01 to 0.99. Default 10%.
min_sample_size: The minimum number of records to retrieve from the population. Default 1000.
"""
size: int
def __init__(self, probability: float = 0.10, min_sample_size: int = 1000):
self.min_sample_size = min_sample_size
self.sample_size_method = BruteForceSampleSize(probability)
def prepare(self, relation: 'Relation',
source_adapter: 'source_adapter') -> None:
"""Runs all nessesary pre-activities and instanciates the sample method.
Prepare will be called before primary query compile time, so it can be used
to do any nessesary pre-compile activites (such as collecting a histogram from the relation).
Args:
relation: The :class:`Relation <snowshu.core.models.relation.Relation>` object to prepare.
source_adapter: The :class:`source adapter <snowshu.adapters.source_adapters.base_source_adapter.BaseSourceAdapter>` instance to use for executing prepare queries.
"""
self.size = max(self.sample_size_method.size(relation.population_size),
self.min_sample_size)
self.sample_method = BernoulliSampleMethod(self.size, units='rows')
def test_div_by_zero():
sample_sizer = BruteForceSampleSize(0.50)
assert sample_sizer.size(0) == 0
def __init__(self, probability: float = 0.10, min_sample_size: int = 1000):
self.min_sample_size = min_sample_size
self.sample_size_method = BruteForceSampleSize(probability)
def test_cochrans():
sample_sizer = BruteForceSampleSize(0.10)
assert sample_sizer.size(100000000) == 10000000