91 lines
2.5 KiB
Python
91 lines
2.5 KiB
Python
"""
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Useful auxiliary data structures for query construction. Not useful outside
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the SQL domain.
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"""
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class Col(object):
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def __init__(self, alias, target, source):
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self.alias, self.target, self.source = alias, target, source
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def as_sql(self, qn, connection):
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return "%s.%s" % (qn(self.alias), qn(self.target.column)), []
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@property
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def output_type(self):
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return self.source
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def relabeled_clone(self, relabels):
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return self.__class__(relabels.get(self.alias, self.alias), self.target, self.source)
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def get_group_by_cols(self):
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return [(self.alias, self.target.column)]
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def get_lookup(self, name):
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return self.output_type.get_lookup(name)
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def get_transform(self, name):
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return self.output_type.get_transform(name)
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def prepare(self):
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return self
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class EmptyResultSet(Exception):
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pass
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class MultiJoin(Exception):
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"""
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Used by join construction code to indicate the point at which a
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multi-valued join was attempted (if the caller wants to treat that
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exceptionally).
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"""
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def __init__(self, names_pos, path_with_names):
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self.level = names_pos
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# The path travelled, this includes the path to the multijoin.
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self.names_with_path = path_with_names
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class Empty(object):
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pass
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class Date(object):
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"""
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Add a date selection column.
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"""
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def __init__(self, col, lookup_type):
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self.col = col
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self.lookup_type = lookup_type
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def relabeled_clone(self, change_map):
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return self.__class__((change_map.get(self.col[0], self.col[0]), self.col[1]))
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def as_sql(self, qn, connection):
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if isinstance(self.col, (list, tuple)):
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col = '%s.%s' % tuple(qn(c) for c in self.col)
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else:
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col = self.col
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return connection.ops.date_trunc_sql(self.lookup_type, col), []
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class DateTime(object):
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"""
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Add a datetime selection column.
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"""
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def __init__(self, col, lookup_type, tzname):
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self.col = col
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self.lookup_type = lookup_type
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self.tzname = tzname
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def relabeled_clone(self, change_map):
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return self.__class__((change_map.get(self.col[0], self.col[0]), self.col[1]))
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def as_sql(self, qn, connection):
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if isinstance(self.col, (list, tuple)):
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col = '%s.%s' % tuple(qn(c) for c in self.col)
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else:
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col = self.col
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return connection.ops.datetime_trunc_sql(self.lookup_type, col, self.tzname)
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