[v3-1-test] Improve get dag grid structure endpoint speed (apache#55942)

* Improve get dag structure endpoint speed

---------
(cherry picked from commit 311277c)

Co-authored-by: dor-bernstein <[email protected]>
Co-authored-by: Elad Kalif <[email protected]>

Author: 2 people

airflow-core/src/airflow/api_fastapi/core_api/routes/ui/grid.py

@@ -161,6 +161,7 @@ def get_dag_structure(
 
     serdags = session.scalars(
         select(SerializedDagModel).where(
+            SerializedDagModel.dag_id == dag_id,
             SerializedDagModel.dag_version_id.in_(
                 select(TaskInstance.dag_version_id)
                 .join(TaskInstance.dag_run)