wForget commented on code in PR #12234:
URL: https://github.com/apache/gluten/pull/12234#discussion_r3356368675


##########
gluten-substrait/src/main/scala/org/apache/gluten/config/GlutenConfig.scala:
##########
@@ -576,6 +576,16 @@ object GlutenConfig extends ConfigRegistry {
       }
       .foreach { case (k, v) => nativeConfMap.put(k, v) }
 
+    // When `orc.force.positional.evolution=true`, vanilla Spark maps ORC 
columns by
+    // position rather than by name (see OrcUtils.requestedColumnIds). The 
Velox ORC reader
+    // must do the same, otherwise name-based matching against a mismatched 
file schema
+    // reads columns back as null/empty. Override the (Velox) 
orcUseColumnNames session conf
+    // so native reads ORC by position too. Harmless for backends that ignore 
this key.
+    // String literal is used because gluten-substrait cannot depend on 
backends-velox.
+    if (conf.getOrElse("spark.hadoop.orc.force.positional.evolution", 
"false").toBoolean) {

Review Comment:
   Would it be better to place this in `getNativeBackendConf`?



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