def __call__(self, rdd: RDD):
column_name = self.column
if self._value_to_index is None:
self.calculate_value_to_index(rdd)
column2id = rdd.context.broadcast(self._value_to_index)
def index_column(row):
"""
Map column_id column to its index value stored in column2id.
WARNING: due to pyspark documentation
(http://spark.apache.org/docs/latest/rdd-programming-guide.html#passing-functions-to-spark)
do not use self inside this function. It will be suboptimal and probably fail to run.
Please contact me if you have troubles: [email protected]
"""
if isinstance(column_name, str):
try:
assert isinstance(row, Row)
row_dict = row.asDict()
row_dict[column_name] = column2id.value[row_dict[column_name]]
return [Row(**row_dict)]
except KeyError:
return []
return [row[:column_name] + (column2id.value[row[column_name]],) +
row[column_name + 1:]]
indexed_rdd = rdd.flatMap(index_column)
column2id.unpersist(blocking=True)
return indexed_rdd
def list_unique_products(rdd: RDD):
"""[task 2a - saves all unique products in transactions into txt]
Args:
rdd (RDD): [spark RDD]
"""
unique = rdd.flatMap(explode).distinct()
unique.coalesce(1).saveAsTextFile("out/out_1_2a.txt")
def make_index(words: list, rdd: RDD):
"""
This function return a RDD containing for each word, the list of article where it's
mentioned.
:param words:
:param rdd:
:return: the word with the list of article containing this word
"""
return rdd.flatMap(
lambda article: filter_words(words, article)).groupByKey()
def list_product_count(rdd: RDD):
"""[task 2b - saves unique count of products into txt]
Args:
rdd (RDD): [description]
"""
sc = SparkContext.getOrCreate()
rdd = sc.parallelize([str(rdd.flatMap(explode).count())])
header = sc.parallelize(["Count:"])
header.union(rdd).coalesce(1).saveAsTextFile("out/out_1_2b.txt")
def list_top_purchased_products(rdd: RDD):
"""[task 3 - saves top 5 purchased products into txt file]
Args:
rdd (RDD): [spark RDD]
"""
sc = SparkContext.getOrCreate()
rdd = (sc.parallelize(
rdd.flatMap(explode).map(lambda w: (w, 1)).reduceByKey(
lambda a, b: a + b).takeOrdered(5,
key=lambda x: -x[1])).coalesce(1))
rdd.saveAsTextFile("out/out_1_3.txt")
def rank_reduce_by_key(words: list, rdd: RDD):
"""
This implementation combine index and computation using `reduceByKey`.
:param words: list of word we would like to rank
:param rdd: dataset of articles
:return: list of pair (word, nb occ)
"""
return rdd.flatMap(lambda article: filter_words(words, article)) \
.map(lambda a: (a[0], 1))\
.reduceByKey(lambda a, b: a + b) \
.sortBy(lambda k: k[1], ascending=False) \
.collect()
def pcy_for_rdd(baskets: RDD, support_threshold_total=support_threshold_total) -> list:
def check_all_subsets_frequent(itemset: list, frequent_itemsets_dict: dict) -> bool:
'''
For example, given a triple ['2', '1', '8'], check if all its subsets ['2', '1'], ['2', '8'], ['1', '8']
are frequent items.
:param itemset:
:return:
'''
itemset_size = len(itemset)
for i in range(itemset_size):
subset = itemset.copy()
subset.pop(i)
try:
_ = frequent_itemsets_dict[tuple(subset)] # 不再需要sorted这个subset，basket已sort
except:
return False
return True
num_baskets = baskets.count()
singleton_counts = baskets.\
flatMap(lambda set: [(item, 1) for item in set]).\
reduceByKey(lambda x,y: x+y).\
filter(lambda pair: pair[1] >= support_threshold_total)
# frequent_singletons_dict = dict(singleton_counts.collect()).keys()
frequent_itemsets_dict = dict(singleton_counts.collect())
# print("frequent_itemsets_dict", frequent_itemsets_dict)
frequent_itemsets_list = [sorted(list(frequent_itemsets_dict.keys()))]
del singleton_counts
gc.collect()
# all_pairs = baskets.flatMap(lambda basket: generate_combination(basket, 2)).persist() # 既然first/second pass都要用，为何不persist
#
# bucket_counts = all_pairs.map(lambda pair:(hash_pair(pair), 1)).reduceByKey(lambda x,y: x+y).collect() # first pass
# bitmap = dict(bucket_counts)
# for key, value in bitmap.items():
# if value >= support_threshold_total:
# bitmap[key] = 1
# else:
# bitmap[key] = 0
current_itemset_size = 2
while True:
# print("current_itemset_size", current_itemset_size)
# if current_itemset_size == 2: # pairs are special
# frequent_itemsets = all_pairs.\
# filter(lambda _: qualified_as_candidate_pair(_, frequent_itemsets_dict, bitmap)).\
# map(lambda pair: (tuple(pair), 1)).\
# reduceByKey(lambda x, y: x + y).\
# filter(lambda pair: pair[1] >= support_threshold_total).persist()
# del all_pairs
# gc.collect()
# else: # 双重filter
frequent_itemsets = baskets.flatMap(lambda basket: generate_combination_with_filter(basket, frequent_itemsets_dict, current_itemset_size)). \
map(lambda itemset: (tuple(itemset), 1)).\
reduceByKey(lambda x,y: x+y).\
filter(lambda pair: pair[1] >= support_threshold_total).persist()
# if frequent_itemsets.count() == 0:
# break
current_size_frequent_itemsets = sorted(frequent_itemsets.keys().collect())
if current_size_frequent_itemsets == []:
break
frequent_itemsets_list.append(current_size_frequent_itemsets)
frequent_itemsets_dict.update(dict.fromkeys(current_size_frequent_itemsets))
# frequent_itemsets_dict.update(dict(frequent_itemsets.collect()))
current_itemset_size += 1
del frequent_itemsets # 也许正确操作应该是释放内存之后再del？我不懂
del current_size_frequent_itemsets
gc.collect()
gc.collect()
return frequent_itemsets_list
def into_words(rdd_in: RDD) -> RDD:
words: RDD = rdd_in.flatMap(lambda x: x.split(' ')).filter(
lambda x: len(x) > 1)
return words.map(lambda x: re.sub(',()', "", x))
