👀 Views: 69 💬 Answers: 1 📅 Created: 2025-06-12

sql-server performance cte recursion SQL

I've looked through the documentation and I'm still confused about I'm working on a personal project and I'm experiencing important performance optimization when executing a recursive Common Table Expression (CTE) in SQL Server 2019..... The CTE is designed to traverse a hierarchy of categories stored in a table, but the execution time seems to increase exponentially with deeper levels of recursion. Here's a simplified version of my query: ```sql WITH RecursiveCategories AS ( SELECT CategoryID, ParentID, CategoryName FROM Categories WHERE ParentID IS NULL UNION ALL SELECT c.CategoryID, c.ParentID, c.CategoryName FROM Categories c INNER JOIN RecursiveCategories rc ON c.ParentID = rc.CategoryID ) SELECT * FROM RecursiveCategories; ``` Initially, this runs quickly for a handful of categories, but as the depth of the hierarchy increases (for instance, with 20+ levels), the execution time can take over several minutes. I believe I've set the appropriate settings for max recursion: ```sql OPTION (MAXRECURSION 100); ``` I've attempted to optimize it further by indexing the `ParentID` and `CategoryID` columns, but I still see no improvement. Additionally, I ran the query with the `SET STATISTICS TIME ON` command to analyze where the bottlenecks might be occurring, and it seems like the time taken for the recursive operations is where most of the delay is happening. If anyone has faced similar issues or has suggestions on how to improve the performance of recursive CTEs in SQL Server, I would greatly appreciate your insights! My development environment is macOS. Is there a better approach? For context: I'm using Sql on Ubuntu 22.04. Any pointers in the right direction?