core_datasource_db performance issue

[Aloth974]

• In file lib/core_datasource_db at line 86 in method get_options() :
  Removing the $q->order() saves about 66% MySQL performances on a table with 6 millions entries, maybe doing it in PHP is better than in MySQL ?
• In file lib/core_datasource_db at line 85 in method get_options() :
  Still, this query is clearly a performance-killer as it takes ~10s to execute on a 6 millions entries table with indexes and a SSD back-end. How could it be improved without losing functionnalities ?