This page outlines the current rate limits and quota limits for BigQuery BI Engine.
During the beta period, BI Engine is subject to the following capacity limits:
The maximum size of a BI Engine reservation is 50 GB per project per location. This limit does not affect the size of the tables that you query. BI Engine loads in-memory only the columns used in your queries, and not the entire table. Additionally, data stored inside BI Engine is compressed.
The data model size remains limited to 10 GB per table. This implies that if you have a 50 GB reservation per project per location, BI Engine will limit the reservation per table to 10 GB. The rest of the available reservation will be used for other tables in the project.
Changes in capacity limits are announced via the BI Engine release notes.
If you run a query that produces query results larger than the size of your BI Engine capacity, the BI Engine self-tuning feature uses BigQuery slots to run the query. When BigQuery slots are used to run a query, you are charged based on BigQuery on-demand query pricing for the query job. When slots are used to run a query, all BigQuery quotas and limits on query jobs apply.