Better resource utilization for non-caching global joins

Detail name	Value
Changelog Number	7537
Type	Improvement
Status	Resolved
Fix Versions	Exasol 7.0.0
Resolution Date	2020-09-11

Background

Several types of global join implementations exist in Exasol. The so called non-caching global join executes a streaming global join without any join result caching. For every key in a pipeline an independent index lookup and remote node data prefetch is executed.

This global join implementation is fast as it does not have to maintain large data caches in TEMP. Nevertheless, there was potential for improvement in CPU and network utilization, especially on systems with many cores and efficient networks.

Improvement

The non-caching global join has been optimized to better utilize CPU (thread parallelism) and network resources, and hence, to reduce query durations.