feat: allow native Iceberg scans with non-identity transform residuals

Author: Shekharrajak

spark/src/main/scala/org/apache/comet/rules/CometScanRule.scala

@@ -478,29 +478,33 @@ case class CometScanRule(session: SparkSession) extends Rule[SparkPlan] with Com
             false
           }
 
-        // Check for unsupported transform functions in residual expressions
-        // iceberg-rust can only handle identity transforms in residuals; all other transforms
-        // (truncate, bucket, year, month, day, hour) must fall back to Spark
+        // Check for transform functions in residual expressions
+        // Non-identity transforms (truncate, bucket, year, month, day, hour) in residuals
+        // are now supported - they skip row-group filtering and are handled post-scan by CometFilter.
+        // This is less optimal than row-group filtering but still allows native execution.
         val transformFunctionsSupported =
           try {
             IcebergReflection.findNonIdentityTransformInResiduals(metadata.tasks) match {
               case Some(transformType) =>
-                // Found unsupported transform
-                fallbackReasons +=
-                  s"Iceberg transform function '$transformType' in residual expression " +
-                    "is not yet supported by iceberg-rust. " +
-                    "Only identity transforms are supported."
-                false
+                // Found non-identity transform - log info and continue with native scan
+                // Row-group filtering will skip these predicates, but post-scan filtering will apply
+                logInfo(
+                  s"Iceberg residual contains transform '$transformType' - " +
+                    "row-group filtering will skip this predicate, " +
+                    "post-scan filtering by CometFilter will apply instead.")
+                true // Allow native execution
               case None =>
-                // No unsupported transforms found - safe to use native execution
+                // No non-identity transforms - optimal row-group filtering will apply
                 true
             }
           } catch {
             case e: Exception =>
-              // Reflection failure - cannot verify safety, must fall back
-              fallbackReasons += "Iceberg reflection failure: Could not check for " +
-                s"transform functions in residuals: ${e.getMessage}"
-              false
+              // Reflection failure - log warning but allow native execution
+              // The predicate conversion will handle unsupported cases gracefully
+              logWarning(
+                s"Could not check for transform functions in residuals: ${e.getMessage}. " +
+                  "Continuing with native scan.")
+              true
           }
 
         // Check for unsupported struct types in delete files