| """ |
| 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 Aggregate(object): |
| """ |
| Base class for all aggregate-related classes (min, max, avg, count, sum). |
| """ |
| def relabel_aliases(self, change_map): |
| """ |
| Relabel the column alias, if necessary. Must be implemented by |
| subclasses. |
| """ |
| raise NotImplementedError |
| |
| def as_sql(self, quote_func=None): |
| """ |
| Returns the SQL string fragment for this object. |
| |
| The quote_func function is used to quote the column components. If |
| None, it defaults to doing nothing. |
| |
| Must be implemented by subclasses. |
| """ |
| raise NotImplementedError |
| |
| class Count(Aggregate): |
| """ |
| Perform a count on the given column. |
| """ |
| def __init__(self, col='*', distinct=False): |
| """ |
| Set the column to count on (defaults to '*') and set whether the count |
| should be distinct or not. |
| """ |
| self.col = col |
| self.distinct = distinct |
| |
| 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, quote_func=None): |
| if not quote_func: |
| quote_func = lambda x: x |
| if isinstance(self.col, (list, tuple)): |
| col = ('%s.%s' % tuple([quote_func(c) for c in self.col])) |
| elif hasattr(self.col, 'as_sql'): |
| col = self.col.as_sql(quote_func) |
| else: |
| col = self.col |
| if self.distinct: |
| return 'COUNT(DISTINCT %s)' % col |
| else: |
| return 'COUNT(%s)' % col |
| |
| class Date(object): |
| """ |
| Add a date selection column. |
| """ |
| def __init__(self, col, lookup_type, date_sql_func): |
| self.col = col |
| self.lookup_type = lookup_type |
| self.date_sql_func = date_sql_func |
| |
| 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, quote_func=None): |
| if not quote_func: |
| quote_func = lambda x: x |
| if isinstance(self.col, (list, tuple)): |
| col = '%s.%s' % tuple([quote_func(c) for c in self.col]) |
| else: |
| col = self.col |
| return self.date_sql_func(self.lookup_type, col) |
| |
