From 16d21f6401436c1f5fd3aff6c09857bf6e222ced Mon Sep 17 00:00:00 2001
From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Mon, 13 Mar 2006 02:53:51 +0000
Subject: [PATCH] added selectfirst_by/selectone_by, selectone throws 
 exception if more than one row returned, courtesy J.Ellis

---
 CHANGES                          |  3 +++
 lib/sqlalchemy/mapping/mapper.py | 45 ++++++++++++++++++++------------
 2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/CHANGES b/CHANGES
index b22f271a9e..72890daca2 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,9 @@ correctly, also relations set up against a mapper with inherited mappers will
 create joins against the table that is specific to the mapper itself (i.e. and
 not any tables that are inherited/are further down the inheritance chain),
 this can be overridden by using custom primary/secondary joins.
+- added J.Ellis patch to mapper.py so that selectone() throws an exception 
+if query returns more than one object row, selectfirst() to not throw the 
+exception. also adds selectfirst_by (synonymous with get_by) and selectone_by
 - added onupdate parameter to Column, will exec SQL/python upon an update
 statement.Also adds "for_update=True" to all DefaultGenerator subclasses
 - added user-contributed support for Oracle table reflection; still
diff --git a/lib/sqlalchemy/mapping/mapper.py b/lib/sqlalchemy/mapping/mapper.py
index a77c2db12f..7254d70bdc 100644
--- a/lib/sqlalchemy/mapping/mapper.py
+++ b/lib/sqlalchemy/mapping/mapper.py
@@ -253,7 +253,7 @@ class Mapper(object):
         populate_existing = kwargs.get('populate_existing', False)
         
         result = util.HistoryArraySet()
-        if len(mappers):
+        if mappers:
             otherresults = []
             for m in mappers:
                 otherresults.append(util.HistoryArraySet())
@@ -273,10 +273,9 @@ class Mapper(object):
         for value in imap.values():
             objectstore.get_session().register_clean(value)
 
-        if len(mappers):
-            return [result] + otherresults
-        else:
-            return result
+        if mappers:
+            result.extend(otherresults)
+        return result
             
     def get(self, *ident):
         """returns an instance of the object based on the given identifier, or None
@@ -374,7 +373,7 @@ class Mapper(object):
         e.g.   u = usermapper.get_by(user_name = 'fred')
         """
         x = self.select_whereclause(self._by_clause(*args, **params), limit=1)
-        if len(x):
+        if x:
             return x[0]
         else:
             return None
@@ -393,6 +392,18 @@ class Mapper(object):
         e.g.   result = usermapper.select_by(user_name = 'fred')
         """
         return self.select_whereclause(self._by_clause(*args, **params))
+    
+    def selectfirst_by(self, *args, **params):
+        """works like select_by(), but only returns the first result by itself, or None if no 
+        objects returned.  Synonymous with get_by()"""
+        return self.get_by(*args, **params)
+
+    def selectone_by(self, *args, **params):
+        """works like selectfirst(), but throws an error if not exactly one result was returned."""
+        ret = self.select_by(*args, **params)
+        if len(ret) == 1:
+            return ret[0]
+        raise InvalidRequestError('Multiple rows returned for selectone')
 
     def count_by(self, *args, **params):
         """returns the count of instances based on the given clauses and key/value criterion.
@@ -448,16 +459,23 @@ class Mapper(object):
         else:
             raise AttributeError(key)
         
-    def selectone(self, *args, **params):
+    def selectfirst(self, *args, **params):
         """works like select(), but only returns the first result by itself, or None if no 
         objects returned."""
         params['limit'] = 1
         ret = self.select(*args, **params)
-        if len(ret):
+        if ret:
             return ret[0]
         else:
             return None
             
+    def selectone(self, *args, **params):
+        """works like selectfirst(), but throws an error if not exactly one result was returned."""
+        ret = self.select(*args, **params)
+        if len(ret) == 1:
+            return ret[0]
+        raise InvalidRequestError('Multiple rows returned for selectone')
+            
     def select(self, arg = None, **kwargs):
         """selects instances of the object from the database.  
         
@@ -983,12 +1001,5 @@ def class_mapper(class_):
     """given a class, returns the primary Mapper associated with the class."""
     try:
         return mapper_registry[class_]
-    except KeyError:
-        pass
-    except AttributeError:
-        pass
-    raise InvalidRequestError("Class '%s' has no mapper associated with it" % class_.__name__)
-    
-
-
-
+    except (KeyError, AttributeError):
+        raise InvalidRequestError("Class '%s' has no mapper associated with it" % class_.__name__)
-- 
2.47.2