So far I have not needed this but it sounds logical. And an easy patch as given.
e = ~db.person.name e is an expression meaning "person.name DESC" so e = ~e should be "person.name" not "person.name DESC DESC" +1 from me Denes. On Nov 29, 10:17 am, mdipierro <[email protected]> wrote: > This should be automatic behavior in the new dal (dal.py). > I do not think it is work spending time changing this in the current > dal (sql.py). > > Massimo > > On Nov 29, 9:09 am, iiijjjiii <[email protected]> wrote: > > > Does it make sense to modify the gluon.sql Expression __invert__ > > method so a double invert is possible. > > > Currently this produces an error: > > > print db().select(db.person.name, orderby=~~db.person.name) > > > ProgrammingError: (1064, "You have an error in your SQL syntax; > > check the manual that corresponds to your MySQL server version for the > > right syntax to use near 'DESC' at line 1") > > > The cause of the error is obvious when you look at the SQL query. > > > SELECT person.name FROM person ORDER BY person.name DESC DESC > > > The second invert adds an additional 'DESC' which makes the query > > invalid. > > > I tried this and it worked. > > > def __invert__(self): > > if str(self)[-5:] == ' DESC': > > return Expression(str(self)[:-5], None, None) > > else: > > return Expression(str(self) + ' DESC', None, None) > > > To explain why a double invert is useful, I have a function that > > returns the rows from a query and the order of the rows is determined > > by parameters. > > > def people(order_expr, reverse=False) > > if False: > > orderby = order_expr > > else: > > orderby = ~order_expr > > return db().select(db.person.ALL, orderby=order_by) > > > It is used in a report. Each field in the report has a default order > > expression. The default order direction for most fields is ascending, > > but for some fields, eg updated_on, the default order is more > > intuitive as descending. The report will allow the user to switch the > > direction with a click. The code simply toggles the reverse parameter. > > I'd like the function to handle any of these combinations. > > > people(db.person.name) > > people(db.person.name, reverse=True) > > people(~db.person.updated_on) > > people(~db.person.updated_on, reverse=True) > > > I am not familiar with the web2py code enough to be aware of the > > effects of changing the __invert__ so my suggestion might have some > > unwanted results. Hopefully others can provide input. > >
