diff --git a/api/migrations/versions/2025_09_17_1515-68519ad5cd18_knowledge_pipeline_migrate.py b/api/migrations/versions/2025_09_17_1515-68519ad5cd18_knowledge_pipeline_migrate.py
index c6f8818852..742cfc345a 100644
--- a/api/migrations/versions/2025_09_17_1515-68519ad5cd18_knowledge_pipeline_migrate.py
+++ b/api/migrations/versions/2025_09_17_1515-68519ad5cd18_knowledge_pipeline_migrate.py
@@ -156,7 +156,7 @@ def upgrade():
     sa.Column('type', sa.String(20), nullable=False),
     sa.Column('file_id', models.types.StringUUID(), nullable=False),
     sa.PrimaryKeyConstraint('id', name=op.f('workflow_node_execution_offload_pkey')),
-    sa.UniqueConstraint('node_execution_id', 'type', name=op.f('workflow_node_execution_offload_node_execution_id_key'), postgresql_nulls_not_distinct=False)
+    sa.UniqueConstraint('node_execution_id', 'type', name=op.f('workflow_node_execution_offload_node_execution_id_key'))
     )
     with op.batch_alter_table('datasets', schema=None) as batch_op:
         batch_op.add_column(sa.Column('keyword_number', sa.Integer(), server_default=sa.text('10'), nullable=True))
diff --git a/api/models/workflow.py b/api/models/workflow.py
index 5f604a51a8..e61005953e 100644
--- a/api/models/workflow.py
+++ b/api/models/workflow.py
@@ -890,12 +890,18 @@ class WorkflowNodeExecutionModel(Base):  # This model is expected to have `offlo
 class WorkflowNodeExecutionOffload(Base):
     __tablename__ = "workflow_node_execution_offload"
     __table_args__ = (
+        # PostgreSQL 14 treats NULL values as distinct in unique constraints by default,
+        # allowing multiple records with NULL values for the same column combination.
+        #
+        # This behavior allows us to have multiple records with NULL node_execution_id,
+        # simplifying garbage collection process.
         UniqueConstraint(
             "node_execution_id",
             "type",
-            # Treat `NULL` as distinct for this unique index, so
-            # we can have mutitple records with `NULL` node_exeution_id, simplify garbage collection process.
-            postgresql_nulls_not_distinct=False,
+            # Note: PostgreSQL 15+ supports explicit `nulls distinct` behavior through
+            # `postgresql_nulls_not_distinct=False`, which would make our intention clearer.
+            # We rely on PostgreSQL's default behavior of treating NULLs as distinct values.
+            # postgresql_nulls_not_distinct=False,
         ),
     )
     _HASH_COL_SIZE = 64