"""
Useful auxilliary data structures for query construction. Not useful outside
the SQL domain.
"""
class EmptyResultSet(Exception):
pass
class FullResultSet(Exception):
pass
class MultiJoin(Exception):
"""
Used by join construction code to indicate the point at which a
multi-valued join was attempted (if the caller wants to treat that
exceptionally).
"""
def __init__(self, level):
self.level = level
class Empty(object):
pass
class RawValue(object):
def __init__(self, value):
self.value = value
class Date(object):
"""
Add a date selection column.
"""
def __init__(self, col, lookup_type):
self.col = col
self.lookup_type = lookup_type
def relabel_aliases(self, change_map):
c = self.col
if isinstance(c, (list, tuple)):
self.col = (change_map.get(c[0], c[0]), c[1])
def as_sql(self, qn, connection):
if isinstance(self.col, (list, tuple)):
col = '%s.%s' % tuple([qn(c) for c in self.col])
else:
col = self.col
return connection.ops.date_trunc_sql(self.lookup_type, col)
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