Microsoft Fabric DirectLake on Delta Parquet & Power BI Copilot

[!NOTE] DirectLake is a revolutionary storage mode in Microsoft Fabric that combines the sub-second speed of Import mode with the real-time freshness and zero data duplication of DirectQuery.

1. How DirectLake Works

• Traditional Import: Copies data from lakehouse files into an internal VertiPaq model.
• DirectQuery: Sends real-time SQL queries to a data warehouse.
• DirectLake: The VertiPaq engine loads Delta Lake Parquet files directly from OneLake into memory on demand without importing or duplicating data!
  • If a query requests data that exceeds memory, it gracefully falls back to DirectQuery.

Staff Architecture: Fabric Lakehouse Serving, Copilot Semantic Prep & Git Integration (.pbip)

• Preparing Semantic Models for Power BI Copilot (AI-Ready Metadata): LLMs inside Copilot/Q&A fail on cryptic column codes like AMT_01_USD_V2 or duplicated OrderDate fields across 5 tables. Add rich Descriptions, Synonyms, clean human business names, and Hide redundant technical surrogate keys (DimCustomerKey) in Model View so Copilot picks the right measure unambiguously!
• Power BI Project (.pbip + TMDL) GitOps: Ditch monolithic opaque binary .pbix files shared over SharePoint. Save as .pbip (TMDL human-readable text format) under Git so data engineers code-review DAX measure edits in pull requests and run CI validation via Tabular Editor Best Practice Analyzer (BPA).
• Row-Level Security (RLS) + Object-Level Security (OLS): Enforce USERPRINCIPALNAME() dynamic RLS via a compact security bridge table (SecurityUserRegion) directly inside the semantic model so both visuals AND Copilot AI summaries strictly respect user permissions.