NOT IN vs LEFT ANTI JOIN: A Performance Comparison
When filtering data based on exclusion criteria, the choice between NOT IN and LEFT ANTI JOIN can significantly impact query performance. This post demonstrates why LEFT ANTI JOIN is typically the better choice. < Revised and generated with help of Claude > Original Approach (Inefficient) SELECT product_id, product_category FROM products_dim WHERE region_id = 100 AND product_id NOT IN ( SELECT product_id FROM products_dim WHERE region_id = 200 ) AND product_category IS NOT NULL Optimized Approach (Recommended) SELECT a.product_id, a.product_category FROM products_dim a LEFT ANTI JOIN ( SELECT DISTINCT product_id FROM products_dim WHERE region_id = 200 ) b ON a.product_id = b.product_id WHERE a.region_id = 100 AND a.product_category IS NOT NULL Why This Works Both queries return exactly the same result: products from region 100 that don’t exist in region 200. Key Differences Aspect NOT IN LEFT ANTI JOIN Performance Slower, less optimized Faster, better optimized by Spark Broadcast Risk Can trigger unwanted broadcasts Better control, prevents large broadcasts Execution Plan Subquery execution Efficient join strategy NULL Handling Unpredictable with NULLs Predictable behavior Bottom Line LEFT ANTI JOIN prevents broadcast errors while delivering the same results faster. When working with large datasets, this optimization can make a substantial difference in query execution time and resource utilization.