Why does this only partially optimize:

select * ;
   from history ;
   into cursor xtemp ;
   where ( ( ltStart <= tCreated ) and ( tCreated < ltStop ) ) ;
   order by iMachineID, tCreated

to get it to fully optimize it has to be written:

select * ;
   from history ;
   into cursor xtemp ;
   where ( ( tCreated >= ltStart ) and ( tCreated < ltStop ) ) ;
   order by iMachineID, tCreated

Why does the field have to appear on the left side or the operator??? Is this documented somewhere?

I'd prefer to to write things more like the algebraic ltStart <= X < ltStop. But evidently rushmore is persnickety about coding that way. There is are indexes on tCreated and iMachineID.