diff --git a/src/common/src/hash/consistent_hash/compat.rs b/src/common/src/hash/consistent_hash/compat.rs
index 395e462d4ad31..0040a79f780fa 100644
--- a/src/common/src/hash/consistent_hash/compat.rs
+++ b/src/common/src/hash/consistent_hash/compat.rs
@@ -92,6 +92,17 @@ impl VnodeCount {
     }
 }
 
+/// A trait for checking whether a table/fragment is a singleton.
+pub trait IsSingleton {
+    /// Returns `true` if the table/fragment is a singleton.
+    ///
+    /// By singleton, we mean that all data read from or written to the storage belongs to
+    /// the only `SINGLETON_VNODE`. This must be consistent with the behavior of
+    /// [`TableDistribution`](crate::hash::table_distribution::TableDistribution::new).
+    /// As a result, the `vnode_count` of such table/fragment can be `1`.
+    fn is_singleton(&self) -> bool;
+}
+
 /// A trait for accessing the vnode count field with backward compatibility.
 ///
 /// # `maybe_`?
@@ -117,28 +128,37 @@ pub trait VnodeCountCompat {
     }
 }
 
+impl IsSingleton for risingwave_pb::catalog::Table {
+    fn is_singleton(&self) -> bool {
+        self.distribution_key.is_empty()
+            && self.dist_key_in_pk.is_empty()
+            && self.vnode_col_index.is_none()
+    }
+}
 impl VnodeCountCompat for risingwave_pb::catalog::Table {
     fn vnode_count_inner(&self) -> VnodeCount {
-        VnodeCount::from_protobuf(self.maybe_vnode_count, || {
-            self.distribution_key.is_empty()
-                && self.dist_key_in_pk.is_empty()
-                && self.vnode_col_index.is_none()
-        })
+        VnodeCount::from_protobuf(self.maybe_vnode_count, || self.is_singleton())
     }
 }
 
+impl IsSingleton for risingwave_pb::plan_common::StorageTableDesc {
+    fn is_singleton(&self) -> bool {
+        self.dist_key_in_pk_indices.is_empty() && self.vnode_col_idx_in_pk.is_none()
+    }
+}
 impl VnodeCountCompat for risingwave_pb::plan_common::StorageTableDesc {
     fn vnode_count_inner(&self) -> VnodeCount {
-        VnodeCount::from_protobuf(self.maybe_vnode_count, || {
-            self.dist_key_in_pk_indices.is_empty() && self.vnode_col_idx_in_pk.is_none()
-        })
+        VnodeCount::from_protobuf(self.maybe_vnode_count, || self.is_singleton())
     }
 }
 
+impl IsSingleton for risingwave_pb::meta::table_fragments::Fragment {
+    fn is_singleton(&self) -> bool {
+        matches!(self.distribution_type(), FragmentDistributionType::Single)
+    }
+}
 impl VnodeCountCompat for risingwave_pb::meta::table_fragments::Fragment {
     fn vnode_count_inner(&self) -> VnodeCount {
-        VnodeCount::from_protobuf(self.maybe_vnode_count, || {
-            matches!(self.distribution_type(), FragmentDistributionType::Single)
-        })
+        VnodeCount::from_protobuf(self.maybe_vnode_count, || self.is_singleton())
     }
 }
diff --git a/src/common/src/hash/table_distribution.rs b/src/common/src/hash/table_distribution.rs
index 822db591c1577..a91f48f6589af 100644
--- a/src/common/src/hash/table_distribution.rs
+++ b/src/common/src/hash/table_distribution.rs
@@ -20,7 +20,7 @@ use risingwave_pb::plan_common::StorageTableDesc;
 
 use crate::array::{Array, DataChunk, PrimitiveArray};
 use crate::bitmap::Bitmap;
-use crate::hash::VirtualNode;
+use crate::hash::{IsSingleton, VirtualNode};
 use crate::row::Row;
 use crate::util::iter_util::ZipEqFast;
 
@@ -64,7 +64,10 @@ impl TableDistribution {
             .map(|&k| k as usize)
             .collect_vec();
         let vnode_col_idx_in_pk = table_desc.vnode_col_idx_in_pk.map(|k| k as usize);
-        Self::new(vnodes, dist_key_in_pk_indices, vnode_col_idx_in_pk)
+
+        let this = Self::new(vnodes, dist_key_in_pk_indices, vnode_col_idx_in_pk);
+        assert_eq!(this.is_singleton(), table_desc.is_singleton());
+        this
     }
 
     pub fn new(
diff --git a/src/stream/src/common/table/state_table.rs b/src/stream/src/common/table/state_table.rs
index 3ada0afd71625..55957af9e6e5b 100644
--- a/src/stream/src/common/table/state_table.rs
+++ b/src/stream/src/common/table/state_table.rs
@@ -29,7 +29,7 @@ use risingwave_common::bitmap::Bitmap;
 use risingwave_common::catalog::{
     get_dist_key_in_pk_indices, ColumnDesc, ColumnId, TableId, TableOption,
 };
-use risingwave_common::hash::{VirtualNode, VnodeBitmapExt};
+use risingwave_common::hash::{IsSingleton, VirtualNode, VnodeBitmapExt};
 use risingwave_common::row::{self, once, CompactedRow, Once, OwnedRow, Row, RowExt};
 use risingwave_common::types::{DataType, Datum, DefaultOrd, DefaultOrdered, ScalarImpl};
 use risingwave_common::util::column_index_mapping::ColIndexMapping;
@@ -363,6 +363,7 @@ where
 
         let distribution =
             TableDistribution::new(vnodes, dist_key_in_pk_indices, vnode_col_idx_in_pk);
+        assert_eq!(distribution.is_singleton(), table_catalog.is_singleton());
 
         let pk_data_types = pk_indices
             .iter()