Thanks, Michael
i end with the following:
#############
from sqlalchemy.sql.expression import _Function
class year( _Function):
__visit_name__ = 'year'
def __init__(self, value):
self.value = value
_Function.__init__( self, self.__visit_name__)
def _compiler_dispatch(self, compiler, **kargs):
val = compiler.preparer.format_column( self.value, use_table=
True)
if compiler.dialect.name == 'postgres':
return "extract( %s from %s)" % ( self.name, val)
elif compiler.dialect.name == 'sqlite':
format_char = 'Y'
pfx = 'strftime( "%' + format_char + '",'
return pfx + ('%s)' % val)
else:
return '%s( %s)' % ( self.name, val)
year._compiler_dispatch = _compiler_dispatch
############
cheers,
stefan
On 18 Март, 19:26, "Michael Bayer" <[email protected]> wrote:
> we'll be adding a feature for this soon. here is a non-public way to do
> it for now which will work throughout 0.5:
>
> from sqlalchemy.sql.expression import ClauseElement
>
> class year(ClauseElement):
> __visit_name__ = 'year'
> def __init__(self, value):
> self.value = value
>
> def _compiler_dispatch(self, compiler):
> if compiler.dialect.name == 'postgres':
> return "pg_year(%s)" % self.value
> else:
> return "sqlite_year(%s)" % self.value
> year._compiler_dispatch = _compiler_dispatch
>
> che wrote:
>
> > Hi,
>
> > i need to add several functions to all dialects that i'll plan to use
> > in order to be fully database-independent.
> > Does anybody have tips how to achieve this?
> > For example i want to add function year( date) to sqlite and postgres
> > dialects.
>
> > TIA,
> > Stefan
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