Starts at 2:15:00 in this video — SQL Warehouse full course — profiling (2:15:00)
Photon
Photon is Databricks’ vectorized engine for SQL warehouses (and some Spark workloads). Benefits: faster scans, joins, aggregations on Delta. It is not a dashboard theme and not a UC tag. When a question asks why DBSQL is fast, the stack is Photon + Delta pruning + warehouse, not Oracle-style B-tree indexes by default.
Query Profile
After a statement, open query details → See query profile. You get a DAG with time, rows, peak memory, I/O. Hunt:
- Exploding joins (row counts jump after a join)
- Full scans (predicate not on cluster/partition keys)
- Unnecessary sorts
- Skew
You typically need to own the query or have Can monitor on the warehouse.
Query Insights
The platform may rank insights (bytes pruned, missing filters). Treat them as hints; still read the DAG. The outline groups Insights and Profiler as how you identify poorly performing queries.