[GitHub] [spark] HyukjinKwon commented on a change in pull request #27702: [SPARK-30955][SQL] Exclude Generate output when aliasing in nested column pruning

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HyukjinKwon commented on a change in pull request #27702: [SPARK-30955][SQL] Exclude Generate output when aliasing in nested column pruning
URL: https://github.com/apache/spark/pull/27702#discussion_r384946240
 
 

 ##########
 File path: sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
 ##########
 @@ -3394,15 +3395,25 @@ class SQLQuerySuite extends QueryTest with SharedSparkSession with AdaptiveSpark
     }
   }
 
-  test("SPARK-30870: Column pruning shouldn't alias a nested column if it means the whole " +
-    "structure") {
-    val df = sql(
-      """
-        |SELECT explodedvalue.field
-        |FROM VALUES array(named_struct('field', named_struct('a', 1, 'b', 2))) AS (value)
-        |LATERAL VIEW explode(value) AS explodedvalue
-      """.stripMargin)
-    checkAnswer(df, Row(Row(1, 2)) :: Nil)
+  test("SPARK-30870: Column pruning shouldn't alias a nested column for the whole structure") {
+    withTable("t") {
+      val df = sql(
+        """
+          |SELECT value
+          |FROM VALUES array(named_struct('field', named_struct('a', 1, 'b', 2))) AS (value)
+        """.stripMargin)
+      df.write.format("parquet").saveAsTable("t")
 
 Review comment:
   Sorry if I am being dumb here but I can't fully follow why LocalRelation matters here. How does the current fix relate to the test fix here?
   
   If we concern about `ConvertToLocalRelation`, it seems not effective here:
   
   ```
   
   == Parsed Logical Plan ==
   'Project ['explodedvalue.field]
   +- 'Generate 'explode('value), false, as, ['explodedvalue]
      +- 'SubqueryAlias AS
         +- 'UnresolvedInlineTable [value], [List('array('named_struct(field, 'named_struct(a, 1, b, 2))))]
   
   == Analyzed Logical Plan ==
   field: struct<a:int,b:int>
   Project [explodedvalue#219.field AS field#220]
   +- Generate explode(value#218), false, as, [explodedvalue#219]
      +- SubqueryAlias AS
         +- LocalRelation [value#218]
   
   == Optimized Logical Plan ==
   Project [explodedvalue#219.field AS field#220]
   +- Generate explode(value#218), [0], false, as, [explodedvalue#219]
      +- LocalRelation [value#218]
   
   == Physical Plan ==
   *(1) Project [explodedvalue#219.field AS field#220]
   +- Generate explode(value#218), false, [explodedvalue#219]
      +- LocalTableScan [value#218]
   ```

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