feat: enable native Iceberg reader by default (#3819)

Author: andygrove

benchmarks/tpc/README.md

@@ -179,8 +179,8 @@ sudo ./drop-caches.sh
 python3 run.py --engine comet-iceberg --benchmark tpch
 ```
 
-The benchmark uses `spark.comet.scan.icebergNative.enabled=true` to enable Comet's native iceberg-rust
-integration. Verify native scanning is active by checking for `CometIcebergNativeScanExec` in the
+The benchmark uses Comet's native iceberg-rust integration, which is enabled by default.
+Verify native scanning is active by checking for `CometIcebergNativeScanExec` in the
 physical plan output.
 
 ### create-iceberg-tables.py options

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

@@ -140,7 +140,7 @@ object CometConf extends ShimCometConf {
           "Iceberg tables are read directly through native execution, bypassing Spark's " +
           "DataSource V2 API for better performance.")
       .booleanConf
-      .createWithDefault(false)
+      .createWithDefault(true)
 
   val COMET_ICEBERG_DATA_FILE_CONCURRENCY_LIMIT: ConfigEntry[Int] =
     conf("spark.comet.scan.icebergNative.dataFileConcurrencyLimit")

docs/source/user-guide/latest/iceberg.md

@@ -26,8 +26,8 @@ then serialized to Comet's native execution engine (see
 [PR #2528](https://github.com/apache/datafusion-comet/pull/2528)).
 
 The example below uses Spark's package downloader to retrieve Comet 0.14.0 and Iceberg
-1.8.1, but Comet has been tested with Iceberg 1.5, 1.7, 1.8, 1.9, and 1.10. The native
-Iceberg reader is enabled by default.
+1.8.1, but Comet has been tested with Iceberg 1.5, 1.7, 1.8, 1.9, and 1.10. The native Iceberg
+reader is enabled by default. To disable it, set `spark.comet.scan.icebergNative.enabled=false`.
 
 ```shell
 $SPARK_HOME/bin/spark-shell \