- added optional constructor to sql.ColumnCollection

- mapper sets its "primary_key" attribute to be the ultimately decided primary_key column collection post-compilation
- added compare() method to MapperProperty, defines a comparison operation of the columns represented by the property to some value
- all the above combines into today's controversial feature: saying query.select_by(somerelationname=someinstance) will create the join of the primary key columns represented by "somerelationname"'s mapper to the actual primary key in "someinstance".
- docs for the above

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql.py b/lib/sqlalchemy/sql.py
index f6e23d583..323173cc5 100644
--- a/lib/sqlalchemy/sql.py
+++ b/lib/sqlalchemy/sql.py
@@ -676,6 +676,9 @@ class ColumnCollection(util.OrderedProperties):
     
     overrides the __eq__() method to produce SQL clauses between sets of
     correlated columns."""
+    def __init__(self, *cols):
+        super(ColumnCollection, self).__init__()
+        [self.add(c) for c in cols]
     def add(self, column):
         """add a column to this collection.