SQL Server 2017: Performance implementing Recursive CTEs Leading to Timeouts
I'm wondering if anyone has experience with I'm performance testing and I'm stuck trying to I've hit a wall trying to After trying multiple solutions online, I still can't figure this out..... I'm stuck on something that should probably be simple. I'm working with important performance optimization when using a recursive CTE in SQL Server 2017. The CTE is intended to retrieve hierarchical data from an employee table, but it often times out or takes much longer than expected to execute, especially when the hierarchy is deep. I've tried optimizing the query, but I still end up with execution times exceeding 30 seconds. Here’s the CTE I’m currently using: ```sql WITH EmployeeHierarchy AS ( SELECT EmployeeID, ManagerID, Name, 0 AS Level FROM Employees WHERE ManagerID IS NULL -- Starting point for the recursion UNION ALL SELECT e.EmployeeID, e.ManagerID, e.Name, eh.Level + 1 FROM Employees e INNER JOIN EmployeeHierarchy eh ON e.ManagerID = eh.EmployeeID ) SELECT * FROM EmployeeHierarchy; ``` I’ve ensured that indices are created on the `ManagerID` and `EmployeeID` columns to improve JOIN performance. I also tried limiting the number of levels with a `WHERE` clause in the recursive part, but it didn’t help much. Additionally, I tested the execution plan, which shows a lot of logical reads and an expensive nested loop join. When the hierarchy has more than 5 levels, the query consistently times out. I receive the following behavior message: ``` The query has timed out. ``` I’m wondering if there are specific best practices for optimizing recursive CTEs, or if there’s a more efficient approach I could take, such as using a different method to retrieve hierarchical data. Any suggestions would be greatly appreciated! Am I missing something obvious? I'm working on a web app that needs to handle this. What am I doing wrong? This issue appeared after updating to Sql 3.11. Any ideas what could be causing this? My team is using Sql for this microservice. Any pointers in the right direction? For context: I'm using Sql on Windows 11. This is happening in both development and production on Windows 11. Cheers for any assistance!