I have a dataframe where I am using groupBy on the key and using collect_list to create an array of struct using col1 and col2. I want to sort the structs inside collect_list by the 2nd element (col2) after forming the collect_list.
I am not sure if I sort the dataframe by col2 initially and then do collect_list it will preserve the sort order or not (I found yes and no both answers in Spark). So I prefer to sort after collect_list is created since my next logic depends on the sort order. I tried udf which sometimes works, but sometimes it's throwing an error.
import pyspark.sql.functions as F
from pyspark.sql.functions import collect_list, collect_set, expr, struct
import operator
from operator import itemgetter
def sorter(key_value_list):
res= sorted(key_value_list, key=lambda x:x[1], reverse=True)
return [ [item[0], item[1]] for item in res]
The return here (return [ [item[0], item[1]] for item in res]) I also tried the below, but nothing worked. Only the above statement works sometimes. But on the bulk data it shows error.
return [ concat_ws('|',[item[0],item[1]) for item in res]
return [ array([item[0],item[1]) for item in res]
sort_udf = F.udf(sorter)
df1=df.groupBy("group_key").agg( F.collect_list ( F.struct("col1","col2")).alias("key_value"))
df1.withColumn("sorted_key_value", sort_udf("key_value")).show(truncate=False)
df1.printSchema()
Input:
group_key col1 col2
123 a 5
123 a 6
123 b 6
123 cd 3
123 d 2
123 ab 9
456 d 4
456 ad 6
456 ce 7
456 a 4
456 s 3
Normal output without sorting:
| group_key | key_value_arr |
|---|---|
| 123 | [[a, 5], [a, 6], [b, 6], [cd, 3], [d 2], [ab, 9]] |
| 456 | [[d, 4], [ad, 6], [ce, 7], [a, 4], [s, 3]] |
Intended output. When I get this output I get a string returned. I want a array of string.
| group_key | key_value_arr |
|---|---|
| 123 | [[ab, 9], [a, 6], [b, 6], [a, 5], [cd, 3], [d 2]] |
| 456 | [[ce, 7], [ad, 6], [d, 4], [a, 4], [s, 3]] |
Error on bulk data:
File "/hadoop/6/yarn/local/usercache/b_incdata_rw/appcache/application_1660704390900_2796904/container_e3797_1660704390900_2796904_01_000002/py4j-0.10.7-src.zip/py4j/protocol.py", line 328, in get_return_value
format(target_id, ".", name), value)
Py4JJavaError: An error occurred while calling o184.showString.
Another way I tried to return array of string (col1 | delimited with col2)
def sorter(key_value_list):
l = []
s = ""
res = sorted(key_value_list, key=lambda x:x[1], reverse=True)
for item in res:
s = F.concat_ws('|', item[0], item[1])
l.append(s)
return l
sort_udf = F.udf(sorter, ArrayType(StringType()))
df6 = df4.withColumn("sorted_key_value", sort_udf("key_value"))
df6.show(truncate=False)
df6.printSchema()
I tried to return res directly as a list that also has same error.
File "/hadoop/10/yarn/local/usercache/b_incdata_rw/appcache/application_1660704390900_2799810/container_e3797_1660704390900_2799810_01_000453/pyspark.zip/pyspark/sql/functions.py", line 1398, in concat_ws
return Column(sc._jvm.functions.concat_ws(sep, _to_seq(sc, cols, _to_java_column)))
AttributeError: 'NoneType' object has no attribute '_jvm'
3rd approach tried
def def_sort(x):
return sorted(x, key=lambda x:x.split('|')[1], reverse=True)
udf_sort = F.udf(def_sort, ArrayType(StringType()))
df_full_multi2.withColumn("sorted_list", array_distinct(udf_sort("key_value"))).show(100, truncate=False)
I get intended result as below
| group_key | sorted_list |
|---|---|
| 123 | [ab|9, a|6, b|6, a|5, cd|3, d|2] |
| 456 | [[ce|7, ad|6, d|4, a|4, s|3] |
However, when I run it write to parquet I get error
An error occurred while calling o178.parquet.Caused by: org.apache.spark.SparkException: Job aborted due to stage failure: Task 807 in stage 2.0 failed 4 times, most recent failure: Lost task 807.3 in stage 2.0 (TID 3495, hdc42-mcc10-01-1110-4105-004-tess0029.stratus.rno.ebay.com, executor 1006): ExecutorLostFailure (executor 1006 exited caused by one of the running tasks) Reason: Container killed by YARN for exceeding memory limits. 21.1 GB of 21 GB physical memory used. Consider boosting spark.yarn.executor.memoryOverhead.
Driver stacktrace: at org.apache.spark.sql.execution.datasources.FileFormatWriter$.write(FileFormatWriter.scala:196) File "/hadoop/10/yarn/local/usercache/b_incdata_rw/appcache/application_1663728370843_1731/container_e3798_1663728370843_1731_01_000001/py4j-0.10.7-src.zip/py4j/protocol.py", line 328, in get_return_value
format(target_id, ".", name), value)
Py4JJavaError: An error occurred while calling o178.parquet.
CodePudding user response：
- create struct the opposite way - first "col2", then "col1"
- sort the array descending using
sort_array(... , False) - flip the fields inside struct using
transform
Input:
from pyspark.sql import functions as F
df = spark.createDataFrame(
[(123, 'a', 5),
(123, 'a', 6),
(123, 'b', 6),
(123, 'cd', 3 ),
(123, 'd', 2),
(123, 'ab', 9),
(456, 'd', 4 ),
(456, 'ad', 6 ),
(456, 'ce', 7 ),
(456, 'a', 4 ),
(456, 's', 3 )],
['group_key', 'col1', 'col2'])
Script:
df1 = (df
.groupBy("group_key")
.agg(F.sort_array(F.collect_list(F.struct("col2", "col1")), False).alias("key_value"))
)
df2 = df1.withColumn("key_value", F.expr("transform(key_value, x -> struct(x.col1, x.col2))"))
df2.show(truncate=0)
# --------- --------------------------------------------------
# |group_key|key_value |
# --------- --------------------------------------------------
# |123 |[{ab, 9}, {b, 6}, {a, 6}, {a, 5}, {cd, 3}, {d, 2}]|
# |456 |[{ce, 7}, {ad, 6}, {d, 4}, {a, 4}, {s, 3}] |
# --------- --------------------------------------------------
If you need a more advanced sorting, you may create a comparator function. Refer to this question for examples on sorting arrays of struct.
In case you want array of string:, use this:
df1 = (df
.groupBy("group_key")
.agg(F.sort_array(F.collect_list(F.struct("col2", "col1")), False).alias("key_value"))
)
df2 = df1.withColumn("key_value", F.expr("transform(key_value, x -> concat(x.col1, '|', x.col2))"))
df2.show(truncate=0)
# --------- --------------------------------
# |group_key|key_value |
# --------- --------------------------------
# |123 |[ab|9, b|6, a|6, a|5, cd|3, d|2]|
# |456 |[ce|7, ad|6, d|4, a|4, s|3] |
# --------- --------------------------------
CodePudding user response：
I see another issue now. My next logic is to take this key_value list and traverse by the sort order. The first col1 I encounter, I store it to another list "t", if it has 2 tokens like 'a' and 'b' as in 'ab' , I store them to "t" as well. If I find 'a', 'b' or 'ab' in any of the next col1 I discard them. If there are multiple tokens with same col2 value I need to sort those tokens lexicographically so that the logic produces same result every time since I use the col2 values in the t_val list for final calculation.
`def func(kv):
t=[]
t_val=[]
for x in kv:
key = str(x.split('|')[0])
value = Decimal(str(x.split('|')[1]))
if (key in t) or ( (len(key)==2 and key[0] in t) or (len(key)==2 and key[1] in t) ):
elif len(key)==2:
t.append(key)
t.append(key[0])
t.append(key[1])
t_val.append(value)
elif len(key)==1:
t.append(key)
t_val.append(value)`
udf_c = udf(func, StringType())
r = df_sorted2.select(udf_c('key_value').alias('fnl_c'))
Below input and out can be list of lists as well.
Input
group_key key_value
123 [ab|9, ad|9, ac|9, a|5, cd|3, e|2 d|2]
456 [ce|7, ad|7, d|4, a|4, s|3 k|3]
desired output - lexicographically sorted by col1
group_key key_value
123 [ab|9, ac|9, ad|9, a|5, cd|3, d|2 e|2]
456 [ad|7, ce|7, a|4, d|4, k|3 s|3]