cleaned up strategy to determine number of mitosis partitions ("pieces"):
cleaned up strategy to determine number of mitosis partitions ("pieces"):

- If the BAT is larger than 1/GDKnr_threads of main memory,
  split it into GDKnr_threads or more partitions such that
  each partition is smaller than 1/GDKnr_threads of main memory.

- Otherwise, if the BAT has more than MINPARTCNT (= 100000) BUNs,
  split it into at most GDKnr_threads partitions such that
  each partition has at least MINPARTCNT BUNs.

- With --forcemito (aka. --debug=536870912), e.g., during testing,
  split also small BATs into up to GDKnr_threads non-empty partitions.

- Limit number of partitions to max. MAXSLICES (=256)
  to prevent plan explosion.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb