diff options
Diffstat (limited to 'webapp/django/db/models/sql/datastructures.py')
-rw-r--r-- | webapp/django/db/models/sql/datastructures.py | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/webapp/django/db/models/sql/datastructures.py b/webapp/django/db/models/sql/datastructures.py new file mode 100644 index 0000000000..913d8fde25 --- /dev/null +++ b/webapp/django/db/models/sql/datastructures.py @@ -0,0 +1,103 @@ +""" +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) + |