https://cdelmonte.dev/tags/datafusion/ Recent content in Datafusion on cdelmonte.dev https://cdelmonte.dev/og-default.png https://cdelmonte.dev/og-default.png Hugo -- 0.147.7 en-us Mon, 12 Oct 2026 00:00:00 +0000 https://cdelmonte.dev/explainers/sorted-files-ordered-scan/ Mon, 12 Oct 2026 00:00:00 +0000 https://cdelmonte.dev/explainers/sorted-files-ordered-scan/ A purchases table, one Parquet file per day, every file sorted by customer: you would expect a GROUP BY customer to use that order, yet EXPLAIN often shows it ignored. This explainer follows the ordering from the file scan to the aggregate in Apache DataFusion, shows where it gets lost, how to read it in the plan, and what you can change.