[GitHub] [spark] Yikun commented on a change in pull request #35191: [SPARK-37491][PYTHON]Fix Series.asof for unsorted values

[GitBox <gi...@apache.org>]

Yikun commented on a change in pull request #35191:
URL: https://github.com/apache/spark/pull/35191#discussion_r784446470



##########
File path: python/pyspark/pandas/series.py
##########
@@ -5228,22 +5228,62 @@ def asof(self, where: Union[Any, List]) -> Union[Scalar, "Series"]:
             where = [where]
         index_scol = self._internal.index_spark_columns[0]
         index_type = self._internal.spark_type_for(index_scol)
+        from pyspark.sql.functions import struct, lit, explode, col, row_number
+
+        column_prefix_constant = "col_"
         cond = [
-            F.max(F.when(index_scol <= SF.lit(index).cast(index_type), self.spark.column))
+            F.when(
+                index_scol <= SF.lit(index).cast(index_type),
+                struct(
+                    lit(column_prefix_constant + str(index)).alias("identifier"),
+                    self.spark.column.alias("Koalas"),
+                ),
+            ).alias(column_prefix_constant + str(index))
             for index in where
         ]
+        cond.append(index_scol)
         sdf = self._internal.spark_frame.select(cond)
+        columns = [cols for cols in sdf.columns if cols.startswith("col")]
+        sdf = sdf.withColumn("combined_cols", F.array(columns)).drop(*columns)
+        sdf = (
+            sdf.select(index_scol, explode("combined_cols").alias("values"))
+            .withColumn("identifier", col("values.identifier"))
+            .withColumn("value", col("values.Koalas"))
+            .drop("values")
+            .na.drop(subset="value")

Review comment:
       BTW, there was [a complain in lint CI](https://github.com/pralabhkumar/spark/runs/4801311278?check_suite_focus=true#step:15:23), it should be a bug on type hint of `na.drop`, I submit the error on [1].
   
   You could just use `dropna(subset="value")` instead of `.na.drop(subset="value")` to work around.
   
   [1] https://github.com/apache/spark/pull/35201




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