Drill provides a parameter to set the memory per query as a static number which defaults to 2 GB. This number is a wonderful setting for the default Drillbit configuration of 8 GB heap; it allows 2-3 concurrent queries. But, as Drillbit memory increases, the default becomes a bit constraining. While users can change the setting, they seldom do.
In addition, provide an option that sets memory as a percent of total memory. If the allocation is 10%, say, and total memory is 128 GB, then each query gets ~13GB, which is a big improvement.
The existing option acts as a floor: the query must receive at least that much memory.
New option should be documented - planner.memory.percent_per_query
Default - 0.05 (which is equivalent to 5 %)
To disable feature set to 0.
More information can be found in pull request description.