Question

我有一个df1 spark数据帧

id     transactions
1      [1, 2, 3, 5]
2      [1, 2, 3, 6]
3      [1, 2, 9, 8]
4      [1, 2, 5, 6]

root
 |-- id: int (nullable = true)
 |-- transactions: array (nullable = false)
     |-- element: int(containsNull = true)
 None

我有一个df2 spark数据帧

items   cost
  [1]    1.0
  [2]    1.0
 [2, 1]  2.0
 [6, 1]  2.0

root
 |-- items: array (nullable = false)
    |-- element: int (containsNull = true)
 |-- cost: int (nullable = true)
 None

我想检查items列中的所有数组元素是否都在Transaction列中。

第一行（[1, 2, 3, 5]）包含项列中的[1],[2],[2, 1]。因此，我需要总结它们的相应费用：1.0 + 1.0 + 2.0 = 4.0

我想要的输出是

id     transactions    score
1      [1, 2, 3, 5]   4.0
2      [1, 2, 3, 6]   6.0
3      [1, 2, 9, 8]   4.0
4      [1, 2, 5, 6]   6.0

我尝试对collect() / toLocalIterator使用循环，但这似乎并不有效。我将拥有大量数据。

我认为创建这样的UDF可以解决它。但是会引发错误。

from pyspark.sql.functions import udf
def containsAll(x,y):
  result =  all(elem in x  for elem in y)

  if result:
    print("Yes, transactions contains all items")    
  else :
    print("No")

 contains_udf = udf(containsAll)
 dataFrame.withColumn("result", 
 contains_udf(df2.items,df1.transactions)).show()

还是还有其他办法？

Answer 1

2.4之前的有效udf（请注意，它不必返回某些内容

from pyspark.sql.functions import udf

@udf("boolean")
def contains_all(x, y):
    if x is not None and y is not None:
        return set(y).issubset(set(x))

在2.4或更高版本中，无需udf：

from pyspark.sql.functions import array_intersect, size

def contains_all(x, y):
    return size(array_intersect(x, y)) == size(y)

用法：

from pyspark.sql.functions import col, sum as sum_, when

df1 = spark.createDataFrame(
   [(1, [1, 2, 3, 5]), (2, [1, 2, 3, 6]), (3, [1, 2, 9, 8]), (4, [1, 2, 5, 6])],
   ("id", "transactions")
)

df2 = spark.createDataFrame(
    [([1], 1.0), ([2], 1.0), ([2, 1], 2.0), ([6, 1], 2.0)],
    ("items", "cost")
)


(df1
    .crossJoin(df2).groupBy("id", "transactions")
    .agg(sum_(when(
        contains_all("transactions", "items"), col("cost")
    )).alias("score"))
    .show())

结果：

+---+------------+-----+                                                        
| id|transactions|score|
+---+------------+-----+
|  1|[1, 2, 3, 5]|  4.0|
|  4|[1, 2, 5, 6]|  6.0|
|  2|[1, 2, 3, 6]|  6.0|
|  3|[1, 2, 9, 8]|  4.0|
+---+------------+-----+

如果df2较小，则可以将其用作局部变量：

items = sc.broadcast([
    (set(items), cost) for items, cost in df2.select("items", "cost").collect()
])

def score(y):
    @udf("double")
    def _(x):
        if x is not None:
            transactions = set(x)
            return sum(
                cost for items, cost in y.value 
                if items.issubset(transactions))
    return _


df1.withColumn("score", score(items)("transactions")).show()

+---+------------+-----+
| id|transactions|score|
+---+------------+-----+
|  1|[1, 2, 3, 5]|  4.0|
|  2|[1, 2, 3, 6]|  6.0|
|  3|[1, 2, 9, 8]|  4.0|
|  4|[1, 2, 5, 6]|  6.0|
+---+------------+-----+

最后有可能爆炸并加入

from pyspark.sql.functions import explode

costs = (df1
    # Explode transactiosn
    .select("id", explode("transactions").alias("item"))
    .join(
        df2 
            # Add id so we can later use it to identify source
            .withColumn("_id", monotonically_increasing_id().alias("_id"))
             # Explode items
            .select(
                "_id", explode("items").alias("item"), 
                # We'll need size of the original items later
                size("items").alias("size"), "cost"), 
         ["item"])
     # Count matches in groups id, items
     .groupBy("_id", "id", "size", "cost")
     .count()
     # Compute cost
     .groupBy("id")
     .agg(sum_(when(col("size") == col("count"), col("cost"))).alias("score")))

costs.show()

+---+-----+                                                                      
| id|score|
+---+-----+
|  1|  4.0|
|  3|  4.0|
|  2|  6.0|
|  4|  6.0|
+---+-----+

，然后将结果与原始df1一起返回，

df1.join(costs, ["id"])

但这不是那么简单的解决方案，并且需要多次改组。与笛卡尔积（crossJoin）相比，它可能仍然更可取，但这取决于实际数据。

检查存在于另一个数组pyspark中的数组的所有元素

1 个答案: