在 pyspark 中保留至少一个元素满足条件的组

Question

I've been trying to reproduce in pyspark something that is fairly easy to do in Pandas, but I've been struggling for a while now. Say I have the following dataframe:

df = pd.DataFrame({'a':[1,2,2,1,1,2], 'b':[12,5,1,19,2,7]})
print(df)
   a   b
0  1  12
1  2   5
2  2   1
3  1  19
4  1   2
5  2   7

And the list

l = [5,1]

What I'm trying to do, is to group by a , and if any of the elements in b are in the list, then return True for all values in the group. Then we could use the result to index the dataframe. The Pandas equivalent of this, would be:

df[df.b.isin(l).groupby(df.a).transform('any')]

   a  b
1  2  5
2  2  1
5  2  7

Reproducible dataframe in pyspark:

from pyspark.sql import SparkSession
spark = SparkSession.builder.getOrCreate()

df = pd.DataFrame({'a':[1,2,2,1,1,2], 'b':[12,5,1,19,2,7]})
sparkdf = spark.createDataFrame(df)

I was currently going in the direction of grouping by a and applying a pandasUDF, though there's surely a better way to do this using spark only.

Answer 1

I've figured out a simple enough solution. The first step is to filter out rows where the values in b are in the list using isin and filter , and then keeping the unique grouping keys ( a ) in a list.

Then by merging back with the dataframe on a we keep groups contained in the list:

unique_a = (sparkdf.filter(f.col('b').isin(l))
                   .select('a').distinct())
sparkdf.join(unique_a, 'a').show()

+---+---+
|  a|  b|
+---+---+
|  2|  5|
|  2|  1|
|  2|  7|
+---+---+