chore: drop leftover JVM Parquet helpers and the native_datafusion scan name (#4385)

Author: andygrove

.claude/skills/bug-triage/SKILL.md

@@ -65,8 +65,7 @@ For each issue, review the title and body and determine:
 2. **Area labels** (zero or more): from the area table in the guide
    (`area:writer`, `area:shuffle`, `area:aggregation`, `area:scan`,
    `area:expressions`, `area:ffi`, `area:ci`) plus the pre-existing area
-   indicators (`native_datafusion`, `native_iceberg_compat`, `spark 4`,
-   `spark sql tests`).
+   indicators (`spark 4`, `spark sql tests`).
 3. **Escalation note**: if the issue matches an escalation trigger from the
    guide (e.g., a `priority:high` crash that may also produce wrong results),
    note it in the summary.

native/core/src/parquet/parquet_exec.rs

@@ -38,8 +38,7 @@ use datafusion_datasource::TableSchema;
 use std::collections::HashMap;
 use std::sync::Arc;
 
-/// Initializes a DataSourceExec plan with a ParquetSource. This may be used by either the
-/// `native_datafusion` scan or the `native_iceberg_compat` scan.
+/// Initializes a DataSourceExec plan with a ParquetSource for Comet's native Parquet scan.
 ///
 ///   `required_schema`: Schema to be projected by the scan.
 ///

spark/src/main/java/org/apache/parquet/filter2/predicate/SparkFilterApi.java

@@ -182,14 +182,14 @@ case class CometScanRule(session: SparkSession)
           return scanExec
         }
 
-        nativeDataFusionScan(plan, session, scanExec, r, hadoopConf).getOrElse(scanExec)
+        nativeScan(plan, session, scanExec, r, hadoopConf).getOrElse(scanExec)
 
       case _ =>
         withInfo(scanExec, s"Unsupported relation ${scanExec.relation}")
     }
   }
 
-  private def nativeDataFusionScan(
+  private def nativeScan(
       plan: SparkPlan,
       session: SparkSession,
       scanExec: FileSourceScanExec,

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

@@ -41,7 +41,7 @@ import org.apache.comet.serde.OperatorOuterClass.Operator
 import org.apache.comet.serde.QueryPlanSerde.{exprToProto, serializeDataType}
 
 /**
- * Validation and serde logic for `native_datafusion` scans.
+ * Validation and serde logic for Comet's native Parquet scan.
  */
 object CometNativeScan extends CometOperatorSerde[CometScanExec] with Logging {