Known problems
==============
 - MySQL (at least 5.0.45, 5.0.51) has problems with queries dealing with
 huge rowset. After certain threshold (involving around 500,000 rows) the
 optimizator stop using INDEXes.
    * You can check if it is actually happening with 'EXPLAIN <query>' command,
    * To force usage of indexes it is possible to add "FORCE INDEX (PRIMARY)"
    keyword after table name in SELECT query.
    * The $MYSQL_FORCE_INDEXES configuration option is forces usage of indexes 
    when necesary and is intended to fix the described behaviour.