Forum Discussion
Fabric - rows per table limitation
- 2 years ago
300M is the row limit per table in an F8 SKU where DirectLake will be supported. Any tables above 300M when running on an F8 capacity will fall back to DirectQuery.
What's the error message? 300M is small, even for a F8
300M is the row limit per table in an F8 SKU where DirectLake will be supported. Any tables above 300M when running on an F8 capacity will fall back to DirectQuery.
- frithjof_v2 years ago
Community Champion
I guess this is related to the fact that Direct Lake loads the entire column into the Power BI Vertipaq cache.
Even if the Power BI end user only queries a subset of the rows, there is no WHERE-filter pushdown to the Delta Tables, only column pruning. So the entire column (all rows) will be loaded into memory.
I guess the row limit is a hard limit in the semantic model memory (Direct Lake Vertipaq cache), with the size of the row limit decided by the SKU size.
Filters in the DAX queries are pushed down to the in-memory vertipaq cache, but filters are not further pushed down to the delta tables. Only column pruning is pushed down to the delta tables.
I guess also the delta table version timestamp is pushed down as part of the query to the delta tables. This is relevant if automatic refresh (automatic reframing) is disabled. In this case, the vertipaq cache will load the version from the delta tables as determined by the time of the last reframing operation of the semantic model.
It would be cool if it was possible to do time travel in a direct lake semantic model. I.e. let the owner manually pick which versions of the delta tables to use in the direct lake semantic model.
- AndyDDC2 years ago
Most Valuable Professional
Nope no filter predicate push down into the delta tables via direct lake, all or nothing. Then filtered in the vertipaq by whatever dax/report filters are in place