diff --git a/src/mito2/src/memtable/partition_tree.rs b/src/mito2/src/memtable/partition_tree.rs
index ab29139aec14..7db9a4877b81 100644
--- a/src/mito2/src/memtable/partition_tree.rs
+++ b/src/mito2/src/memtable/partition_tree.rs
@@ -587,7 +587,7 @@ mod tests {
             })
             .push_column_metadata(ColumnMetadata {
                 column_schema: ColumnSchema::new(
-                    "__ts_id",
+                    "__tsid",
                     ConcreteDataType::uint64_datatype(),
                     false,
                 ),
diff --git a/src/mito2/src/memtable/partition_tree/dict.rs b/src/mito2/src/memtable/partition_tree/dict.rs
index 3b0a02026105..52217dc94bc2 100644
--- a/src/mito2/src/memtable/partition_tree/dict.rs
+++ b/src/mito2/src/memtable/partition_tree/dict.rs
@@ -120,7 +120,7 @@ impl KeyDictBuilder {
                 .sum::<usize>()
     }
 
-    /// Finishes the builder.
+    /// Finishes the builder. The key of the second BTreeMap is sparse-encoded bytes.
     pub fn finish(&mut self) -> Option<(KeyDict, BTreeMap<Vec<u8>, PkIndex>)> {
         if self.key_buffer.is_empty() {
             return None;