diff --git a/src/metric-engine/src/data_region.rs b/src/metric-engine/src/data_region.rs
index f9ee734ffc56..5564ef8e7751 100644
--- a/src/metric-engine/src/data_region.rs
+++ b/src/metric-engine/src/data_region.rs
@@ -46,9 +46,9 @@ impl DataRegion {
 
     /// Submit an alter request to underlying physical region.
     ///
-    /// This method will change the semantic type of those given columns.
-    /// [SemanticType::Tag] will become [SemanticType::Field]. The procedure framework
-    /// ensures there is no concurrent conflict.
+    /// This method will change the nullability of those given columns.
+    /// [SemanticType::Tag] will become nullable column as it's shared between
+    /// logical regions.
     ///
     /// Invoker don't need to set up or verify the column id. This method will adjust
     /// it using underlying schema.
@@ -89,7 +89,6 @@ impl DataRegion {
             .enumerate()
             .map(|(delta, mut c)| {
                 if c.semantic_type == SemanticType::Tag {
-                    c.semantic_type = SemanticType::Field;
                     if !c.column_schema.data_type.is_string() {
                         return ColumnTypeMismatchSnafu {
                             column_type: c.column_schema.data_type,
diff --git a/src/metric-engine/src/engine/put.rs b/src/metric-engine/src/engine/put.rs
index 3d4bc1485bfb..f8c12ea78d0c 100644
--- a/src/metric-engine/src/engine/put.rs
+++ b/src/metric-engine/src/engine/put.rs
@@ -123,7 +123,6 @@ impl MetricEngineInner {
     }
 
     /// Perform metric engine specific logic to incoming rows.
-    /// - Change the semantic type of tag columns to field
     /// - Add table_id column
     /// - Generate tsid
     fn modify_rows(&self, table_id: TableId, rows: &mut Rows) -> Result<()> {
@@ -141,18 +140,6 @@ impl MetricEngineInner {
             })
             .collect::<Vec<_>>();
 
-        // generate new schema
-        rows.schema = rows
-            .schema
-            .clone()
-            .into_iter()
-            .map(|mut col| {
-                if col.semantic_type == SemanticType::Tag as i32 {
-                    col.semantic_type = SemanticType::Field as i32;
-                }
-                col
-            })
-            .collect::<Vec<_>>();
         // add table_name column
         rows.schema.push(ColumnSchema {
             column_name: DATA_SCHEMA_TABLE_ID_COLUMN_NAME.to_string(),