Power BI, a business analytics tool developed by Microsoft, offers three different data storage modes: Direct Query, Import Mode, and the newly introduced Direct Lake. Each mode has its unique characteristics and use cases. In this blog post, we will explore these three modes and compare them on multiple parameters.
Direct Query
In Direct Query mode, the Power BI engine queries the data at the source. This can be slow but avoids having to copy the data like with import mode. Any changes at the data source are immediately reflected in the query results. DAX is translated to the native SQL queries which are sent to the relational database.
Import Mode
In import mode, the data is imported into the model and saved in the proprietary *.idf files which are columnar storage files. The data is stored locally, allowing offline access. Performance can be better because the data is cached and optimized for DAX and MDX report queries without having to translate and pass SQL or other types of queries to the data source. However, the Power BI engine must first copy any new data into the model during refresh. Any changes at the source are only picked up with the next model refresh.
Direct Lake
Direct Lake mode is a groundbreaking semantic model capability for analyzing very large data volumes in Power BI. Direct Lake is based on loading parquet-formatted files directly from a data lake without having to query a Lakehouse or Warehouse endpoint, and without having to import or duplicate data into a Power BI model. Direct Lake essentially uses the same concept as the import mode. Because there’s no explicit import process, it’s possible to pick up any changes at the data source as they occur, combining the advantages of both DirectQuery and import modes while avoiding their disadvantages.
Comparison
| Parameter | Direct Query | Import Mode | Direct Lake |
|---|---|---|---|
| Data Source | Queries data at the source | Imports data into the model | Loads parquet-formatted files directly from a data lake |
| Performance | Can be slow | Better performance due to local caching | Performance similar to import mode |
| Data Refresh | Immediate reflection of changes at the data source | Changes picked up during next model refresh | Picks up changes at the data source as they occur |
| Data Storage | No local data storage | Local data storage | No local data storage |
In conclusion, the choice between Direct Query, Import Mode, and Direct Lake depends on the specific requirements of your Power BI project. Each mode has its strengths and is suited to different scenarios. It’s important to understand these differences to make the most of Power BI’s capabilities.