[web2py] how to change a field type from string to decimal?

[Carlos]

Hi,

Is it possible (and how) to change a field type from string to decimal 
without recreating the table?.

There are no records in the table yet, but I would like to know if there's 
a way to accomplish this from web2py (without recreating the database).

The error I get:

<class 'psycopg2.ProgrammingError'> column "xfield__tmp" is of type numeric 
but expression is of type character varying LINE 1: UPDATE xtable SET 
xfield__tmp=xfield; ^ HINT: You will need to rewrite or cast the 
expression. 

I'm using latest web2py trunk with postgresql.

Thanks,

   Carlos