add print function to BlockStreamBase for debuging.
Fixed a bug in LogcialQueryPlan::getOptimalPhysicalPlan()
add getNumberOfBlock() and destory() methods.
add print() and getResultSet virtual method()
convert "getAttribute(unsigned index)const" into "getAttribute(unsigned
offset)const;"
add print() method
Fixed a bug caused by the default construct of Attribute class.
add ResultSet data structure which is used to hold the result data.
query optimization