fixup

backends-velox/src/main/scala/org/apache/gluten/backendsapi/velox/VeloxListenerApi.scala

@@ -73,22 +73,26 @@ class VeloxListenerApi extends ListenerApi with Logging {
       val debugDir = conf.get(GlutenConfig.GLUTEN_DEBUG_KEEP_JNI_WORKSPACE_DIR)
       JniWorkspace.enableDebug(debugDir)
     }
+
+    // Set the system properties.
+    // Use appending policy for children with the same name in a arrow struct vector.
+    System.setProperty("arrow.struct.conflict.policy", "CONFLICT_APPEND")
+
+    // Load supported hive/python/scala udfs
+    UDFMappings.loadFromSparkConf(conf)
+
+    // Initial library loader.
     val loader = JniWorkspace.getDefault.libLoader
 
+    // Load shared native libraries the backend libraries depend on.
     val osName = System.getProperty("os.name")
     if (osName.startsWith("Mac OS X") || osName.startsWith("macOS")) {
       loadLibWithMacOS(loader)
     } else {
       loadLibWithLinux(conf, loader)
     }
 
-    // Set the system properties.
-    // Use appending policy for children with the same name in a arrow struct vector.
-    System.setProperty("arrow.struct.conflict.policy", "CONFLICT_APPEND")
-
-    // Load supported hive/python/scala udfs
-    UDFMappings.loadFromSparkConf(conf)
-
+    // Load backend libraries.
     val libPath = conf.get(GlutenConfig.GLUTEN_LIB_PATH, StringUtils.EMPTY)
     if (StringUtils.isNotBlank(libPath)) { // Path based load. Ignore all other loadees.
       JniLibLoader.loadFromPath(libPath, false)
@@ -98,11 +102,11 @@ class VeloxListenerApi extends ListenerApi with Logging {
       loader.mapAndLoad(VeloxBackend.BACKEND_NAME, false)
     }
 
+    // Initial native backend with configurations.
     val parsed = GlutenConfigUtil.parseConfig(conf.getAll.toMap)
     NativeBackendInitializer.initializeBackend(parsed)
 
-    // inject backend-specific implementations to override spark classes
-    // FIXME: The following set instances twice in local mode?
+    // Inject backend-specific implementations to override spark classes.
     GlutenParquetWriterInjects.setInstance(new VeloxParquetWriterInjects())
     GlutenOrcWriterInjects.setInstance(new VeloxOrcWriterInjects())
     GlutenRowSplitter.setInstance(new VeloxRowSplitter())