Faster hash joiner with vectorized execution

By contrast, in the vectorized execution model, each component of the plan processes an entire batch of columnar data at once, instead of just a single row. The vectorized execution model aims at this simple truth by replacing the fully-general, interpreter-like SQL expression evaluator with a series of specific compiled loops, specialized on datatype and operation, so that the computer can do many more simple tasks in a row before having to step back and make a decision about what to do next. In the Volcano model, each data row is processed one at a time by each operator – a row-by-row execution approach.

Source: www.cockroachlabs.com