Resolve todo

Author: HyukjinKwon

cpp/src/arrow/flight/sql/odbc/odbc_impl/flight_sql_result_set_metadata.cc

@@ -222,7 +222,9 @@ Updatability FlightSqlResultSetMetadata::GetUpdatable(int column_position) {
 bool FlightSqlResultSetMetadata::IsAutoUnique(int column_position) {
   ColumnMetadata metadata = GetMetadata(schema_->field(column_position - 1));
 
-  // TODO: Is AutoUnique equivalent to AutoIncrement?
+  // AUTO_UNIQUE_VALUE (ODBC 3.0+, SQL_DESC_AUTO_UNIQUE_VALUE) is equivalent to
+  // AUTO_INCREMENT (ODBC 2.0, SQL_COLUMN_AUTO_INCREMENT). Both indicate columns
+  // that automatically generate unique values.
   return metadata.GetIsAutoIncrement().ValueOrElse([] { return false; });
 }