[GitHub] [spark] maropu commented on a change in pull request #31887: [SPARK-34794][SQL] fix nested transform issue

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

maropu commented on a change in pull request #31887:
URL: https://github.com/apache/spark/pull/31887#discussion_r607421098



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/functions.scala
##########
@@ -3799,23 +3801,26 @@ object functions {
     ArrayExcept(col1.expr, col2.expr)
   }
 
+  // counter to ensure lambda variable names are unique
+  private val lambdaVarNameCounter = new AtomicInteger(0)

Review comment:
       How about defining a companion object for UnresolvedNamedLambdaVariable like this?
   ```
   
   object UnresolvedNamedLambdaVariable {
   
     // counter to ensure lambda variable names are unique
     private val lambdaVarNameCounter = new AtomicInteger(0)
   
     def apply(args: Seq[String]): UnresolvedNamedLambdaVariable = {
       // add a counter number in the suffix
     }
   }
   ```

##########
File path: sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
##########
@@ -2261,6 +2261,32 @@ class DataFrameFunctionsSuite extends QueryTest with SharedSparkSession {
     assert(ex3.getMessage.contains("cannot resolve 'a'"))
   }
 
+  test("nested transform (DSL)") {

Review comment:
       nit: `nested transform (DSL)` -> `SPARK-34794: nested transform`

##########
File path: sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
##########
@@ -2261,6 +2261,32 @@ class DataFrameFunctionsSuite extends QueryTest with SharedSparkSession {
     assert(ex3.getMessage.contains("cannot resolve 'a'"))
   }
 
+  test("nested transform (DSL)") {
+    val df = Seq(
+        (Seq(1, 2, 3), Seq("a", "b", "c"))
+    ).toDF("numbers", "letters")
+
+    checkAnswer(
+        df.select(
+          flatten(
+            transform(
+              $"numbers",
+              (number: Column) => transform(

Review comment:
       I think we need exhaustive tests for this issue, e.g., two/three argument cases and their combination cases.




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