add values when reporting conflicting schema merge

Author: Igosuki

datafusion/src/field_util.rs

@@ -269,8 +269,7 @@ impl SchemaExt for Schema {
                         if old_val != &value {
                             return Err(DataFusionError::ArrowError(
                                 ArrowError::InvalidArgumentError(
-                                    "Fail to merge schema due to conflicting metadata."
-                                        .to_string(),
+                                    format!("Fail to merge schema due to conflicting metadata, {} != {}.", old_val, value),
                                 ),
                             ));
                         }