[SPARK-24339][SQL] Prunes the unused columns from child of ScriptTransformation

## What changes were proposed in this pull request?

Modify the strategy in ColumnPruning to add a Project between ScriptTransformation and its child, this strategy can reduce the scan time especially in the scenario of the table has many columns.

## How was this patch tested?

Add UT in ColumnPruningSuite and ScriptTransformationSuite.

Author: Yuanjian Li <[email protected]>

Closes apache#21839 from xuanyuanking/SPARK-24339.

Author: xuanyuanking

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -501,13 +501,16 @@ object ColumnPruning extends Rule[LogicalPlan] {
     case d @ DeserializeToObject(_, _, child) if (child.outputSet -- d.references).nonEmpty =>
       d.copy(child = prunedChild(child, d.references))
 
-    // Prunes the unused columns from child of Aggregate/Expand/Generate
+    // Prunes the unused columns from child of Aggregate/Expand/Generate/ScriptTransformation
     case a @ Aggregate(_, _, child) if (child.outputSet -- a.references).nonEmpty =>
       a.copy(child = prunedChild(child, a.references))
     case f @ FlatMapGroupsInPandas(_, _, _, child) if (child.outputSet -- f.references).nonEmpty =>
       f.copy(child = prunedChild(child, f.references))
     case e @ Expand(_, _, child) if (child.outputSet -- e.references).nonEmpty =>
       e.copy(child = prunedChild(child, e.references))
+    case s @ ScriptTransformation(_, _, _, child, _)
+        if (child.outputSet -- s.references).nonEmpty =>
+      s.copy(child = prunedChild(child, s.references))
 
     // prune unrequired references
     case p @ Project(_, g: Generate) if p.references != g.outputSet =>

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ColumnPruningSuite.scala

@@ -140,6 +140,30 @@ class ColumnPruningSuite extends PlanTest {
     comparePlans(optimized, expected)
   }
 
+  test("Column pruning for ScriptTransformation") {
+    val input = LocalRelation('a.int, 'b.string, 'c.double)
+    val query =
+      ScriptTransformation(
+        Seq('a, 'b),
+        "func",
+        Seq.empty,
+        input,
+        null).analyze
+    val optimized = Optimize.execute(query)
+
+    val expected =
+      ScriptTransformation(
+        Seq('a, 'b),
+        "func",
+        Seq.empty,
+        Project(
+          Seq('a, 'b),
+          input),
+        null).analyze
+
+    comparePlans(optimized, expected)
+  }
+
   test("Column pruning on Filter") {
     val input = LocalRelation('a.int, 'b.string, 'c.double)
     val plan1 = Filter('a > 1, input).analyze

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/ScriptTransformationSuite.scala

@@ -136,6 +136,25 @@ class ScriptTransformationSuite extends SparkPlanTest with TestHiveSingleton {
     }
     assert(e.getMessage.contains("Subprocess exited with status"))
   }
+
+  test("SPARK-24339 verify the result after pruning the unused columns") {
+    val rowsDf = Seq(
+      ("Bob", 16, 176),
+      ("Alice", 32, 164),
+      ("David", 60, 192),
+      ("Amy", 24, 180)).toDF("name", "age", "height")
+
+    checkAnswer(
+      rowsDf,
+      (child: SparkPlan) => new ScriptTransformationExec(
+        input = Seq(rowsDf.col("name").expr),
+        script = "cat",
+        output = Seq(AttributeReference("name", StringType)()),
+        child = child,
+        ioschema = serdeIOSchema
+      ),
+      rowsDf.select("name").collect())
+  }
 }
 
 private case class ExceptionInjectingOperator(child: SparkPlan) extends UnaryExecNode {