An insight after monitoring the mystery sort for a few hours.
The mystery sortings change with time with a peculiar pattern:
- a few (<10) maps may change their postion drastically (500+ or even 1k+ positions) within hours in both directions
-- new postions may be in the middle of the pack or at the sole bottom
-- maps may revert their position back with another major swing
-- those changes are not in line with ratings sort changes by magnitude, which are all <70 positions
- a few (<10) maps may also change their postion slightly (<10 positions)
- other maps usually change their position just because of the changes above
Here is a snapshot of mystery ranks of the maps, which have significatly changed position in 4 hours.
Notice the Clue Special War map, at one point it became the last ranked map in the mystery sort and then it returned to the original position.
map_name T0 T0+3h T0+3.5h T0+4h
Testopia 21 21 21 625
Race to the Island - 2.0 2382 1346 1347 1346
GodStorm 20 20 20 622
Elsass Frei 2374 1343 1345 1344
Element 2378 1344 1346 1345
Economic-Centers 2391 1348 1348 1347
Clue Special War 1742 1747 2653 1745
My guess is that the mystery sort is actually "no sort" and the results are some random noise in database.
Usually databases, when no sorting is specified, tend to return data in the same order, but this is never guaranteed. Maybe someone who knows databases better, may confirm or invalidate whether the observable patten is consistent with such databases' behaviour.