feat: Enable columnar shuffle by default

common/src/main/scala/org/apache/comet/CometConf.scala

@@ -140,14 +140,14 @@ object CometConf {
       .booleanConf
       .createWithDefault(false)
 
-  val COMET_COLUMNAR_SHUFFLE_ENABLED: ConfigEntry[Boolean] = conf(
-    "spark.comet.columnar.shuffle.enabled")
-    .doc(
-      "Force Comet to only use columnar shuffle for CometScan and Spark regular operators. " +
-        "If this is enabled, Comet native shuffle will not be enabled but only Arrow shuffle. " +
-        "By default, this config is false.")
-    .booleanConf
-    .createWithDefault(false)
+  val COMET_COLUMNAR_SHUFFLE_ENABLED: ConfigEntry[Boolean] =
+    conf("spark.comet.columnar.shuffle.enabled")
+      .doc(
+        "Whether to enable Arrow-based columnar shuffle for Comet and Spark regular operators. " +
+          "If this is enabled, Comet prefers columnar shuffle than native shuffle. " +
+          "By default, this config is true.")
+      .booleanConf
+      .createWithDefault(true)
 
   val COMET_SHUFFLE_ENFORCE_MODE_ENABLED: ConfigEntry[Boolean] =
     conf("spark.comet.shuffle.enforceMode.enabled")

common/src/main/scala/org/apache/comet/vector/NativeUtil.scala

@@ -66,7 +66,7 @@ class NativeUtil {
           val arrowArray = ArrowArray.allocateNew(allocator)
           Data.exportVector(
             allocator,
-            getFieldVector(valueVector),
+            getFieldVector(valueVector, "export"),
             provider,
             arrowArray,
             arrowSchema)

common/src/main/scala/org/apache/spark/sql/comet/util/Utils.scala

@@ -242,7 +242,7 @@ object Utils {
             }
           }
 
-          getFieldVector(valueVector)
+          getFieldVector(valueVector, "serialize")
 
         case c =>
           throw new SparkException(
@@ -253,14 +253,15 @@ object Utils {
     (fieldVectors, provider)
   }
 
-  def getFieldVector(valueVector: ValueVector): FieldVector = {
+  def getFieldVector(valueVector: ValueVector, reason: String): FieldVector = {
     valueVector match {
       case v @ (_: BitVector | _: TinyIntVector | _: SmallIntVector | _: IntVector |
           _: BigIntVector | _: Float4Vector | _: Float8Vector | _: VarCharVector |
           _: DecimalVector | _: DateDayVector | _: TimeStampMicroTZVector | _: VarBinaryVector |
           _: FixedSizeBinaryVector | _: TimeStampMicroVector) =>
         v.asInstanceOf[FieldVector]
-      case _ => throw new SparkException(s"Unsupported Arrow Vector: ${valueVector.getClass}")
+      case _ =>
+        throw new SparkException(s"Unsupported Arrow Vector for $reason: ${valueVector.getClass}")
     }
   }
 }