[SPARK-35378][SQL][FOLLOW-UP] Fix incorrect return type in CommandResultExec.executeCollect()

### What changes were proposed in this pull request?

This PR is a follow-up for #32513 and fixes an issue introduced by that patch.

CommandResultExec is supposed to return `UnsafeRow` records in all of the `executeXYZ` methods but `executeCollect` was left out which causes issues like this one:
```
Error in SQL statement: ClassCastException: org.apache.spark.sql.catalyst.expressions.GenericInternalRow
cannot be cast to org.apache.spark.sql.catalyst.expressions.UnsafeRow
```

We need to return `unsafeRows` instead of `rows` in `executeCollect` similar to other methods in the class.

### Why are the changes needed?

Fixes a bug in CommandResultExec.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

I added a unit test to check the return type of all commands.

Closes #36632 from sadikovi/fix-command-exec.

Authored-by: Ivan Sadikov <[email protected]>
Signed-off-by: Wenchen Fan <[email protected]>

Author: sadikovi

sql/core/src/main/scala/org/apache/spark/sql/execution/CommandResultExec.scala

@@ -76,8 +76,8 @@ case class CommandResultExec(
   }
 
   override def executeCollect(): Array[InternalRow] = {
-    longMetric("numOutputRows").add(rows.size)
-    rows.toArray
+    longMetric("numOutputRows").add(unsafeRows.size)
+    unsafeRows
   }
 
   override def executeTake(limit: Int): Array[InternalRow] = {

sql/core/src/test/scala/org/apache/spark/sql/execution/QueryExecutionSuite.scala

@@ -20,6 +20,7 @@ import scala.io.Source
 
 import org.apache.spark.sql.{AnalysisException, FastOperator}
 import org.apache.spark.sql.catalyst.analysis.UnresolvedNamespace
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
 import org.apache.spark.sql.catalyst.plans.QueryPlan
 import org.apache.spark.sql.catalyst.plans.logical.{CommandResult, LogicalPlan, OneRowRelation, Project, ShowTables, SubqueryAlias}
 import org.apache.spark.sql.catalyst.trees.TreeNodeTag
@@ -262,6 +263,14 @@ class QueryExecutionSuite extends SharedSparkSession {
     assert(cmdResultExec.commandPhysicalPlan.isInstanceOf[ShowTablesExec])
   }
 
+  test("SPARK-35378: Return UnsafeRow in CommandResultExecCheck execute methods") {
+    val plan = spark.sql("SHOW FUNCTIONS").queryExecution.executedPlan
+    assert(plan.isInstanceOf[CommandResultExec])
+    plan.executeCollect().foreach { row => assert(row.isInstanceOf[UnsafeRow]) }
+    plan.executeTake(10).foreach { row => assert(row.isInstanceOf[UnsafeRow]) }
+    plan.executeTail(10).foreach { row => assert(row.isInstanceOf[UnsafeRow]) }
+  }
+
   test("SPARK-38198: check specify maxFields when call toFile method") {
     withTempDir { dir =>
       val path = dir.getCanonicalPath + "/plans.txt"