Merged the queryset-refactor branch into trunk.

This is a big internal change, but mostly backwards compatible with existing
code. Also adds a couple of new features.

Fixed #245, #1050, #1656, #1801, #2076, #2091, #2150, #2253, #2306, #2400, #2430, #2482, #2496, #2676, #2737, #2874, #2902, #2939, #3037, #3141, #3288, #3440, #3592, #3739, #4088, #4260, #4289, #4306, #4358, #4464, #4510, #4858, #5012, #5020, #5261, #5295, #5321, #5324, #5325, #5555, #5707, #5796, #5817, #5987, #6018, #6074, #6088, #6154, #6177, #6180, #6203, #6658


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7477 bcc190cf-cafb-0310-a4f2-bffc1f526a37

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)
+