diff --git a/be/src/common/config.h b/be/src/common/config.h
index 3f4a156bd4b3ab..d38c80f219b4c7 100644
--- a/be/src/common/config.h
+++ b/be/src/common/config.h
@@ -464,6 +464,7 @@ CONF_Int32(memory_max_alignment, "16");
 // write buffer size before flush
 CONF_mInt64(write_buffer_size, "209715200");
 
+// max buffer size used in memtable for the aggregated table
 CONF_mInt64(memtable_max_buffer_size, "419430400");
 
 // following 2 configs limit the memory consumption of load process on a Backend.