SPRKPY1043

pyspark.sql.functions.posexplode_outer

Message: pyspark.sql.functions.posexplode_outer has a workaround

Category: Warning

Description

This issue appears when the tool detects the usage of pyspark.sql.functions.posexplode_outer which has a workaround.

Scenarios

There are a couple of scenarios that this method can handle depending on the type of column it is passed as a parameter, it can be a list of values or a map/directory (keys/values).

Scenario 1

Input

Below is an example that shows the usage of posexplode_outer passing a list of values.

df = spark.createDataFrame(
    [
        (1, ["foo", "bar"]),
        (2, []),
        (3, None)],
    ("id", "an_array"))

df.select("id", "an_array", posexplode_outer("an_array")).show()

Output

The tool adds the EWI SPRKPY1043 indicating that a workaround can be implemented.

df = spark.createDataFrame(
    [
        (1, ["foo", "bar"]),
        (2, []),
        (3, None)],
    ("id", "an_array"))
#EWI: SPRKPY1043 => pyspark.sql.functions.posexplode_outer has a workaround, see documentation for more info

df.select("id", "an_array", posexplode_outer("an_array")).show()

Recommended fix

For having the same behavior, use the method functions.flatten sending the outer parameter in True, drop extra columns, and rename index and value column names.

df = spark.createDataFrame(
    [
        (1, ["foo", "bar"]),
        (2, []),
        (3, None)],
    ("id", "an_array"))

df.select(
    flatten(df.an_array, outer=True))\
    .drop("DATA", "SEQ", "KEY", "PATH", "THIS")\
    .rename({"INDEX": "pos", "VALUE": "col"}).show()

Scenario 2

Input

Below is another example of the usage of posexplode_outer passing a map/dictionary (keys/values)

df = spark.createDataFrame(
    [
        (1, {"x": 1.0}),
        (2, {}),
        (3, None)],
    ("id", "a_map"))

df.select(posexplode_outer(df.a_map)).show()

Output

The tool adds the EWI SPRKPY1043 indicating that a workaround can be implemented.

df = spark.createDataFrame(
    [
        (1, {"x": "Ashi Garami"}),
        (2, {}),
        (3, None)],
    ("id", "a_map"))
#EWI: SPRKPY1043 => pyspark.sql.functions.posexplode_outer has a workaround, see documentation for more info

df.select(posexplode_outer(df.a_map)).show()

Recommended fix

As a workaround, you can use functions.row_number to get the position and functions.explode_outer with the name of the field to get the value of the key/value for dictionaries.

df = spark.createDataFrame(
    [
        (1, {"x": "Ashi Garami"}),
        (2,  {}),
        (3, None)],
    ("id", "a_map"))

window = Window.orderBy(col("id").asc())

df.select(
    row_number().over(window).alias("pos"),
          explode_outer(df.a_map)).show()

Note: using row_number is not fully equivalent, because it starts with 1 (not zero as spark method)

Additional recommendations

• For more support, you can email us at [email protected] or post an issue in the SMA.