Adds to Melange a tags framework based on taggable-mixin.
The taggable-mixin allowed only tag per Datastore model. This is extended
framework allows any arbitrary number of tags per Datastore model. Also,
now one can define different models for different Tag types which are all
inherited from the base Tag model provided by taggable-mixin.
The GHOPTask model makes use of 2 tags per model, one for difficulty and the
other for task_type, both using the tags framework.
Reviewed by: Paweł Sołyga
from types import UnicodeType
def gqn(val):
"""
The geographic quote name function; used for quoting tables and
geometries (they use single rather than the double quotes of the
backend quotename function).
"""
if isinstance(val, basestring):
if isinstance(val, UnicodeType): val = val.encode('ascii')
return "'%s'" % val
else:
return str(val)
class SpatialOperation(object):
"""
Base class for generating spatial SQL.
"""
def __init__(self, function='', operator='', result='', beg_subst='', end_subst=''):
self.function = function
self.operator = operator
self.result = result
self.beg_subst = beg_subst
try:
# Try and put the operator and result into to the
# end substitution.
self.end_subst = end_subst % (operator, result)
except TypeError:
self.end_subst = end_subst
@property
def sql_subst(self):
return ''.join([self.beg_subst, self.end_subst])
def as_sql(self, geo_col):
return self.sql_subst % self.params(geo_col)
def params(self, geo_col):
return (geo_col, self.operator)
class SpatialFunction(SpatialOperation):
"""
Base class for generating spatial SQL related to a function.
"""
def __init__(self, func, beg_subst='%s(%s, %%s', end_subst=')', result='', operator=''):
# Getting the function prefix.
kwargs = {'function' : func, 'operator' : operator, 'result' : result,
'beg_subst' : beg_subst, 'end_subst' : end_subst,}
super(SpatialFunction, self).__init__(**kwargs)
def params(self, geo_col):
return (self.function, geo_col)