fix(transfer): allow unquoted gaussdb transfer identifiers

crates/dbx-core/src/sql_dialect/identifiers.rs

@@ -395,6 +395,31 @@ pub(crate) fn quote_transfer_identifier(name: &str, database_type: &DatabaseType
     }
 }
 
+pub(crate) fn transfer_column_identifier(
+    name: &str,
+    database_type: &DatabaseType,
+    quote_target_column_names: bool,
+) -> String {
+    if quote_target_column_names
+        || !matches!(database_type, DatabaseType::Gaussdb | DatabaseType::OpenGauss)
+        || !is_simple_unquoted_identifier(name)
+        || is_postgres_reserved_identifier(&name.to_ascii_lowercase())
+    {
+        quote_transfer_identifier(name, database_type)
+    } else {
+        name.to_string()
+    }
+}
+
+fn is_simple_unquoted_identifier(name: &str) -> bool {
+    let mut chars = name.chars();
+    let Some(first) = chars.next() else {
+        return false;
+    };
+    (first == '_' || first.is_ascii_alphabetic())
+        && chars.all(|ch| ch == '_' || ch == '$' || ch.is_ascii_alphanumeric())
+}
+
 /// Qualified table name for transfer SQL.
 ///
 /// * Without catalog: produces `schema.table` (or just `table` for MySQL family).