diff --git a/src/query/service/src/interpreters/interpreter_merge_into.rs b/src/query/service/src/interpreters/interpreter_merge_into.rs
index b10d0fe80b113..df7273841cf13 100644
--- a/src/query/service/src/interpreters/interpreter_merge_into.rs
+++ b/src/query/service/src/interpreters/interpreter_merge_into.rs
@@ -227,7 +227,7 @@ impl MergeIntoInterpreter {
 
         let insert_only = matches!(merge_type, MergeIntoType::InsertOnly);
 
-        let mut row_id_idx = if !insert_only && !target_build_optimization {
+        let mut row_id_idx = if !insert_only {
             match meta_data
                 .read()
                 .row_id_index_by_table_index(*target_table_idx)
diff --git a/src/query/sql/src/planner/binder/merge_into.rs b/src/query/sql/src/planner/binder/merge_into.rs
index 61f3fd82d6598..6df7be89062bc 100644
--- a/src/query/sql/src/planner/binder/merge_into.rs
+++ b/src/query/sql/src/planner/binder/merge_into.rs
@@ -58,7 +58,6 @@ use crate::IndexType;
 use crate::ScalarBinder;
 use crate::ScalarExpr;
 use crate::Visibility;
-use crate::DUMMY_COLUMN_INDEX;
 
 #[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
 pub enum MergeIntoType {
@@ -438,20 +437,8 @@ impl Binder {
                 .await?,
             );
         }
-        let mut split_idx = DUMMY_COLUMN_INDEX;
-        // find any target table column index for merge_into_split
-        for column in self
-            .metadata
-            .read()
-            .columns_by_table_index(table_index)
-            .iter()
-        {
-            if column.index() != row_id_index {
-                split_idx = column.index();
-                break;
-            }
-        }
-        assert!(split_idx != DUMMY_COLUMN_INDEX);
+
+        let split_idx = row_id_index;
 
         Ok(MergeInto {
             catalog: catalog_name.to_string(),
diff --git a/src/query/sql/src/planner/optimizer/optimizer.rs b/src/query/sql/src/planner/optimizer/optimizer.rs
index 2506f353b1d79..d04d833ee8fe1 100644
--- a/src/query/sql/src/planner/optimizer/optimizer.rs
+++ b/src/query/sql/src/planner/optimizer/optimizer.rs
@@ -494,7 +494,6 @@ async fn optimize_merge_into(opt_ctx: OptimizerContext, plan: Box<MergeInto>) ->
             == 0
         && flag
     {
-        new_columns_set.remove(&plan.row_id_index);
         opt_ctx.table_ctx.set_merge_into_join(MergeIntoJoin {
             merge_into_join_type: MergeIntoJoinType::Left,
             is_distributed: false,
diff --git a/tests/sqllogictests/suites/base/09_fuse_engine/09_0040_merge_into_issue_15643.test b/tests/sqllogictests/suites/base/09_fuse_engine/09_0040_merge_into_issue_15643.test
new file mode 100644
index 0000000000000..9e53be7883358
--- /dev/null
+++ b/tests/sqllogictests/suites/base/09_fuse_engine/09_0040_merge_into_issue_15643.test
@@ -0,0 +1,28 @@
+statement ok
+create or replace database m_test;
+
+statement ok
+use m_test;
+
+statement ok
+create table t(a string, b string, c string, d string, k string);
+
+statement ok
+create table s(a string, b string, c string, d string, k string);
+
+statement ok
+insert into t(k) values('k');
+
+statement ok
+insert into s(k) values('k');
+
+
+query II
+merge into t using s on t.k = s.k when matched then update * when not matched then insert *;
+----
+0 1
+
+query TTTTT
+select * from t;
+----
+NULL NULL NULL NULL k