diff --git a/src/Interpreters/InterpreterInsertQuery.cpp b/src/Interpreters/InterpreterInsertQuery.cpp
index 01fee30a445..5985a7fb7d6 100644
--- a/src/Interpreters/InterpreterInsertQuery.cpp
+++ b/src/Interpreters/InterpreterInsertQuery.cpp
@@ -93,6 +93,8 @@ Block InterpreterInsertQuery::getSampleBlock(
     }
 
     Block table_sample = metadata_snapshot->getSampleBlock();
+
+    /// Process column transformers (e.g. * EXCEPT(a)), asterisks and qualified columns.
     const auto & columns = metadata_snapshot->getColumns();
     auto names_and_types = columns.getOrdinary();
     removeDuplicateColumns(names_and_types);