I am building a manufacturing monitor and I need the data to be as close to real-time as possible. I'm debating between using Import mode with frequent refreshes and DirectQuery. What are the major trade-offs in terms of DAX functionality and report speed? Are there specific limitations in DirectQuery that might prevent me from building complex visualizations?
3 answers
The primary trade-off is performance versus freshness. Import mode is much faster because data is stored in memory and optimized by the VertiPaq engine, but you are limited to scheduled refreshes. DirectQuery provides real-time data but every visual interaction sends a query to the source database, which can be slow if the DB isn't optimized. Additionally, many DAX functions are restricted in DirectQuery, and you cannot use Power Query's "Transform" features as extensively because the logic must be "folded" back to the source SQL.
Have you looked into the "Hybrid Tables" feature in Power BI Premium? It allows you to have historical data in Import mode while keeping the most recent data in DirectQuery within a single table. Would your current licensing allow for Premium features, or are you strictly on a Pro license?
I usually stick with Import mode and use the API to trigger refreshes. DirectQuery can be a nightmare for report performance if you have more than 5 users online.
Mary is right. Unless you absolutely need second-by-second updates, Import mode with an 8-times-a-day refresh (or more on Premium) usually provides a much better user experience.
Joseph, we are currently on a Pro license, so Hybrid tables aren't an option yet. If I stick with DirectQuery, is there a way to optimize the SQL side to make the visual interactions feel snappier for the end users on the manufacturing floor?