A streaming algorithm needs only need to see each incoming item only once.
They work on a stream of data in a single pass.
They are also known as one-touch processing.
Sketch are streaming algorithm that provide an approximate answer in order to answer queries fast (using various randomization techniques)
Sketch data structures are Mergeable (reducable), which enables parallel processing
In each partition, each row is a summary of each dimension combination.
- Druid use it