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103 lines
2.8 KiB
103 lines
2.8 KiB
""" |
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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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|
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class EmptyResultSet(Exception): |
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pass |
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|
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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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