53 lines
1.7 KiB
Python
53 lines
1.7 KiB
Python
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from types import UnicodeType
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def gqn(val):
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"""
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The geographic quote name function; used for quoting tables and
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geometries (they use single rather than the double quotes of the
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backend quotename function).
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"""
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if isinstance(val, basestring):
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if isinstance(val, UnicodeType): val = val.encode('ascii')
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return "'%s'" % val
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else:
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return str(val)
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class SpatialOperation(object):
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"""
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Base class for generating spatial SQL.
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"""
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def __init__(self, function='', operator='', result='', beg_subst='', end_subst=''):
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self.function = function
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self.operator = operator
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self.result = result
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self.beg_subst = beg_subst
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try:
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# Try and put the operator and result into to the
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# end substitution.
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self.end_subst = end_subst % (operator, result)
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except TypeError:
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self.end_subst = end_subst
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@property
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def sql_subst(self):
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return ''.join([self.beg_subst, self.end_subst])
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def as_sql(self, geo_col):
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return self.sql_subst % self.params(geo_col)
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def params(self, geo_col):
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return (geo_col, self.operator)
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class SpatialFunction(SpatialOperation):
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"""
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Base class for generating spatial SQL related to a function.
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"""
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def __init__(self, func, beg_subst='%s(%s, %%s', end_subst=')', result='', operator=''):
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# Getting the function prefix.
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kwargs = {'function' : func, 'operator' : operator, 'result' : result,
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'beg_subst' : beg_subst, 'end_subst' : end_subst,}
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super(SpatialFunction, self).__init__(**kwargs)
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def params(self, geo_col):
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return (self.function, geo_col)
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