Data engineering·Cost, layout and query performance
the query returned four rows and the console says it read two point one terabytes.
Bytes scanned
Also calledscan volume, data scanned
How much data a query actually read from storage, which on most modern warehouses is what you are billed for. It is the number to optimise rather than runtime, because a fast query on a large scan is still expensive and caching makes runtime a liar. It also makes the effect of layout legible: the same query on the same data can differ by three orders of magnitude in bytes scanned depending on partitioning and column selection.