[GLUTEN-11985][VL] Add test for PartialProject with null struct row

backends-velox/src/test/scala/org/apache/gluten/execution/MiscOperatorSuite.scala

@@ -30,11 +30,14 @@ import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types._
 
 import java.nio.file.{Files, Paths}
+import java.sql.Timestamp
 import java.util.concurrent.TimeUnit
 
 import scala.collection.JavaConverters
 import scala.collection.JavaConverters._
 
+case class TsContributor(touch_time: Timestamp)
+
 class MiscOperatorSuite extends VeloxWholeStageTransformerSuite with AdaptiveSparkPlanHelper {
   protected val rootPath: String = getClass.getResource("/").getPath
   override protected val resourcePath: String = "/tpch-data-parquet"
@@ -2258,4 +2261,30 @@ class MiscOperatorSuite extends VeloxWholeStageTransformerSuite with AdaptiveSpa
       }
     }
   }
+
+  test("ColumnarPartialProject for null struct row with timestamp child") {
+    withSQLConf(SQLConf.ANSI_ENABLED.key -> "false") {
+      val structIdentity = udf((p: TsContributor) => p)
+      spark.udf.register("struct_identity", structIdentity)
+
+      withTable("t") {
+        spark.sql("create table t (id int, ts timestamp) using parquet")
+        spark.sql("insert into t values (1, timestamp'2026-01-01 00:00:00')")
+        spark.sql("insert into t values (2, null)")
+
+        runQueryAndCompare(
+          """with v as (
+            |select id, case when ts is null then null else named_struct('touch_time', ts) end as ts
+            |from t
+            |)
+            |select id, case when ts is null then null else struct_identity(ts) end from v
+            |""".stripMargin) {
+          df =>
+            val executedPlan = getExecutedPlan(df)
+            assert(executedPlan.count(_.isInstanceOf[ProjectExec]) == 0)
+            assert(executedPlan.count(_.isInstanceOf[ColumnarPartialProjectExec]) == 1)
+        }
+      }
+    }
+  }
 }