TD-6520 : Refractored the SP to fix DTU Spike

Author: swapnamol-abraham

WebAPI/LearningHub.Nhs.Database/Stored Procedures/Hierarchy/GetNodePathNodes.sql

@@ -11,25 +11,37 @@
 -- 22-06-2023  RS   Switched order of joins to ensure catalogue node is always returned first.
 -- 24-08-2023  RS   Proper fix for ordering issue - STRING_SPLIT doesn't return substrings in order.
 -- 08-09-2023  RS   A further fix for ordering issue that works on SQL Server 2019 (for developer installs).
+-- 17-12-2025  SA   TD-6520 - Refractored the SP to fix the DTU spike.
 -------------------------------------------------------------------------------
 CREATE PROCEDURE [hierarchy].[GetNodePathNodes]
 (
-	@NodePathId INT
+    @NodePathId INT
 )
-
 AS
-
 BEGIN
+    SET NOCOUNT ON;
 
-	SELECT 
-		CAST(value AS INT) AS NodeId,
-		COALESCE(fnv.Name, cnv.Name) AS Name
-	FROM hierarchy.NodePath np
-		CROSS APPLY hub.fn_Split(NodePath, '\') as ss
-		INNER JOIN hierarchy.NodeVersion nv ON nv.NodeId = ss.value
-		LEFT JOIN hierarchy.CatalogueNodeVersion cnv ON cnv.NodeVersionId = nv.Id
-		LEFT JOIN hierarchy.FolderNodeVersion fnv ON fnv.NodeVersionId = nv.Id
-	WHERE np.Id = @NodePathId
-	ORDER BY ss.idx
-
+    -- If NodePath is NVARCHAR, keep types consistent to avoid implicit conversions
+    ;WITH PathParts AS
+    (
+        SELECT
+            ordinal,
+            TRY_CAST(s.value AS int) AS NodeIdInt
+        FROM hierarchy.NodePath AS np
+        CROSS APPLY STRING_SPLIT(np.NodePath, N'\', 1) AS s   -- 1 = ordinal
+        WHERE np.Id = @NodePathId
+    )
+    SELECT
+        pp.NodeIdInt AS NodeId,
+        COALESCE(fnv.Name, cnv.Name) AS Name
+    FROM PathParts AS pp
+    JOIN hierarchy.NodeVersion AS nv
+        ON nv.NodeId = pp.NodeIdInt
+    LEFT JOIN hierarchy.CatalogueNodeVersion AS cnv
+        ON cnv.NodeVersionId = nv.Id
+    LEFT JOIN hierarchy.FolderNodeVersion AS fnv
+        ON fnv.NodeVersionId = nv.Id
+    WHERE pp.NodeIdInt IS NOT NULL
+    ORDER BY pp.ordinal
+    OPTION (RECOMPILE);  -- helps if @NodePathId cardinality varies a lot
 END