diff --git a/shims/spark311cdh/src/main/scala/com/nvidia/spark/rapids/shims/spark311cdh/Spark311CDHShims.scala b/shims/spark311cdh/src/main/scala/com/nvidia/spark/rapids/shims/spark311cdh/Spark311CDHShims.scala
index 40c2c25511f..876d568d622 100644
--- a/shims/spark311cdh/src/main/scala/com/nvidia/spark/rapids/shims/spark311cdh/Spark311CDHShims.scala
+++ b/shims/spark311cdh/src/main/scala/com/nvidia/spark/rapids/shims/spark311cdh/Spark311CDHShims.scala
@@ -22,7 +22,6 @@ import com.nvidia.spark.rapids._
 import com.nvidia.spark.rapids.spark311cdh.RapidsShuffleManager
 
 import org.apache.spark.sql.catalyst.catalog.{CatalogTable, SessionCatalog}
-import org.apache.spark.sql.catalyst.expressions.NamedExpression
 import org.apache.spark.sql.execution._
 import org.apache.spark.sql.execution.columnar.InMemoryTableScanExec
 import org.apache.spark.sql.internal.{SQLConf, StaticSQLConf}
diff --git a/shims/spark313/src/main/scala/org/apache/spark/sql/rapids/shims/spark313/GpuColumnarToRowTransitionExec.scala b/shims/spark313/src/main/scala/org/apache/spark/sql/rapids/shims/spark313/GpuColumnarToRowTransitionExec.scala
index d5be5e14c25..15792ebc72c 100644
--- a/shims/spark313/src/main/scala/org/apache/spark/sql/rapids/shims/spark313/GpuColumnarToRowTransitionExec.scala
+++ b/shims/spark313/src/main/scala/org/apache/spark/sql/rapids/shims/spark313/GpuColumnarToRowTransitionExec.scala
@@ -18,8 +18,11 @@ package org.apache.spark.sql.rapids.shims.spark313
 
 import com.nvidia.spark.rapids.GpuColumnarToRowExecParent
 
+import org.apache.spark.sql.catalyst.expressions.NamedExpression
 import org.apache.spark.sql.execution.{ColumnarToRowTransition, SparkPlan}
 
 case class GpuColumnarToRowTransitionExec(child: SparkPlan,
-   override val exportColumnarRdd: Boolean = false)
-   extends GpuColumnarToRowExecParent(child, exportColumnarRdd) with ColumnarToRowTransition
+    override val exportColumnarRdd: Boolean = false,
+    override val postProjection: Seq[NamedExpression] = Seq.empty)
+    extends GpuColumnarToRowExecParent(child, exportColumnarRdd, postProjection)
+        with ColumnarToRowTransition
diff --git a/sql-plugin/src/main/scala/com/nvidia/spark/rapids/RapidsMeta.scala b/sql-plugin/src/main/scala/com/nvidia/spark/rapids/RapidsMeta.scala
index 8b274ee69a0..27063c8ee38 100644
--- a/sql-plugin/src/main/scala/com/nvidia/spark/rapids/RapidsMeta.scala
+++ b/sql-plugin/src/main/scala/com/nvidia/spark/rapids/RapidsMeta.scala
@@ -1123,19 +1123,26 @@ abstract class TypedImperativeAggExprMeta[INPUT <: TypedImperativeAggregate[_]](
   def aggBufferAttribute: AttributeReference
 
   /**
-   * Returns a buffer converter who can generate a Expression to transform the aggregation
-   * buffer of wrapped function from CPU format to GPU format.
+   * Returns a buffer converter who can generate a Expression to transform the aggregation buffer
+   * of wrapped function from CPU format to GPU format. The conversion occurs on the CPU, so the
+   * generated expression should be a CPU Expression executed by row.
    */
   def createCpuToGpuBufferConverter(): CpuToGpuAggregateBufferConverter =
-    throw new NotImplementedError("")
+    throw new NotImplementedError("The method should be implemented by specific functions")
 
   /**
-   * Returns a buffer converter who can generate a Expression to transform the aggregation
-   * buffer of wrapped function from GPU format to CPU format.
+   * Returns a buffer converter who can generate a Expression to transform the aggregation buffer
+   * of wrapped function from GPU format to CPU format. The conversion occurs on the CPU, so the
+   * generated expression should be a CPU Expression executed by row.
    */
   def createGpuToCpuBufferConverter(): GpuToCpuAggregateBufferConverter =
-    throw new NotImplementedError("")
+    throw new NotImplementedError("The method should be implemented by specific functions")
 
+  /**
+   * Whether buffers of current Aggregate is able to be converted from CPU to GPU format and
+   * reversely in runtime. If true, it assumes both createCpuToGpuBufferConverter and
+   * createGpuToCpuBufferConverter are implemented.
+   */
   val supportBufferConversion: Boolean = false
 }