Ok, this actually doesn't seem like an inherent calc. engine issue, but rather a modelling issue.
As we don't know what your scripted view looks like it's hard to tell, where things go wrong.
However, you might want to look into using the conversion to a number (as mentioned here in the thread already).
Also, when speed is actually your priority, don't perform the conversion over and over. Instead handle this during data loading time or create a generated column.
All we can tell up to hear is that your current model seems to force a intermediate materialization on a huge amount of records. Pretty sure the 10^18 result set is due to a false join condition.
- Lars