| """ |
| A collection of utility routines and classes used by the spatial |
| backends. |
| """ |
| |
| 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, unicode): val = val.encode('ascii') |
| return "'%s'" % val |
| else: |
| return str(val) |
| |
| class SpatialOperation(object): |
| """ |
| Base class for generating spatial SQL. |
| """ |
| sql_template = '%(geo_col)s %(operator)s %(geometry)s' |
| |
| def __init__(self, function='', operator='', result='', **kwargs): |
| self.function = function |
| self.operator = operator |
| self.result = result |
| self.extra = kwargs |
| |
| def as_sql(self, geo_col, geometry='%s'): |
| return self.sql_template % self.params(geo_col, geometry) |
| |
| def params(self, geo_col, geometry): |
| params = {'function' : self.function, |
| 'geo_col' : geo_col, |
| 'geometry' : geometry, |
| 'operator' : self.operator, |
| 'result' : self.result, |
| } |
| params.update(self.extra) |
| return params |
| |
| class SpatialFunction(SpatialOperation): |
| """ |
| Base class for generating spatial SQL related to a function. |
| """ |
| sql_template = '%(function)s(%(geo_col)s, %(geometry)s)' |
| |
| def __init__(self, func, result='', operator='', **kwargs): |
| # Getting the function prefix. |
| default = {'function' : func, |
| 'operator' : operator, |
| 'result' : result |
| } |
| kwargs.update(default) |
| super(SpatialFunction, self).__init__(**kwargs) |
