104 lines
2.8 KiB
Python
104 lines
2.8 KiB
Python
"""
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Useful auxilliary data structures for query construction. Not useful outside
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the SQL domain.
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"""
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class EmptyResultSet(Exception):
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pass
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class FullResultSet(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, level):
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self.level = level
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class Empty(object):
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pass
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class RawValue(object):
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def __init__(self, value):
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self.value = value
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class Aggregate(object):
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"""
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Base class for all aggregate-related classes (min, max, avg, count, sum).
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"""
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def relabel_aliases(self, change_map):
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"""
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Relabel the column alias, if necessary. Must be implemented by
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subclasses.
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"""
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raise NotImplementedError
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def as_sql(self, quote_func=None):
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"""
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Returns the SQL string fragment for this object.
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The quote_func function is used to quote the column components. If
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None, it defaults to doing nothing.
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Must be implemented by subclasses.
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"""
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raise NotImplementedError
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class Count(Aggregate):
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"""
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Perform a count on the given column.
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"""
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def __init__(self, col='*', distinct=False):
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"""
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Set the column to count on (defaults to '*') and set whether the count
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should be distinct or not.
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"""
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self.col = col
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self.distinct = distinct
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def relabel_aliases(self, change_map):
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c = self.col
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if isinstance(c, (list, tuple)):
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self.col = (change_map.get(c[0], c[0]), c[1])
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def as_sql(self, quote_func=None):
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if not quote_func:
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quote_func = lambda x: x
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if isinstance(self.col, (list, tuple)):
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col = ('%s.%s' % tuple([quote_func(c) for c in self.col]))
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elif hasattr(self.col, 'as_sql'):
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col = self.col.as_sql(quote_func)
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else:
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col = self.col
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if self.distinct:
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return 'COUNT(DISTINCT %s)' % col
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else:
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return 'COUNT(%s)' % col
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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, date_sql_func):
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self.col = col
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self.lookup_type = lookup_type
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self.date_sql_func= date_sql_func
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def relabel_aliases(self, change_map):
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c = self.col
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if isinstance(c, (list, tuple)):
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self.col = (change_map.get(c[0], c[0]), c[1])
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def as_sql(self, quote_func=None):
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if not quote_func:
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quote_func = lambda x: x
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if isinstance(self.col, (list, tuple)):
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col = '%s.%s' % tuple([quote_func(c) for c in self.col])
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else:
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col = self.col
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return self.date_sql_func(self.lookup_type, col)
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