undestanding SELECT query execution model ... need help

Hi, I am new to Derby. I am trying to understand Derby's "SELECT" query execution and optimization model at the code level. Can anyone please point me to the right code area and the starting point? Thanks, SQ P.S. I have downloaded the code from SVN repo.

derby.language.logQueryPlan

The manual says that derby.language.logQueryPlan is a systemwide property. Is it possible to set it by JDBC, or only in the derby.properties file? tom

Derby Function

Is there any function for - GROUP BY YEAR(), GROUP BY MONTH(), GROUP BY QUARTER() in derby?