some more tweaks to get more advanced polymorphic stuff to work

1 files changed, 137 insertions, 0 deletions

diff --git a/examples/polymorph/polymorph2.py b/examples/polymorph/polymorph2.py
new file mode 100644
index 000000000..99ee6c34c
--- /dev/null
+++ b/examples/polymorph/polymorph2.py
@@ -0,0 +1,137 @@
+from sqlalchemy import *
+import sys
+
+# this example illustrates a polymorphic load of two classes, where each class has a very 
+# different set of properties
+
+db = create_engine('sqlite://', echo=True, echo_uow=False)
+
+# a table to store companies
+companies = Table('companies', db, 
+   Column('company_id', Integer, primary_key=True),
+   Column('name', String(50))).create()
+
+# we will define an inheritance relationship between the table "people" and "engineers",
+# and a second inheritance relationship between the table "people" and "managers"
+people = Table('people', db, 
+   Column('person_id', Integer, primary_key=True),
+   Column('company_id', Integer, ForeignKey('companies.company_id')),
+   Column('name', String(50))).create()
+   
+engineers = Table('engineers', db, 
+   Column('person_id', Integer, ForeignKey('people.person_id'), primary_key=True),
+   Column('status', String(30)),
+   Column('engineer_name', String(50)),
+   Column('primary_language', String(50)),
+  ).create()
+   
+managers = Table('managers', db, 
+   Column('person_id', Integer, ForeignKey('people.person_id'), primary_key=True),
+   Column('status', String(30)),
+   Column('manager_name', String(50))
+   ).create()
+
+  
+# create our classes.  The Engineer and Manager classes extend from Person.
+class Person(object):
+    def __repr__(self):
+        return "Ordinary person %s" % self.name
+class Engineer(Person):
+    def __repr__(self):
+        return "Engineer %s, status %s, engineer_name %s, primary_language %s" % (self.name, self.status, self.engineer_name, self.primary_language)
+class Manager(Person):
+    def __repr__(self):
+        return "Manager %s, status %s, manager_name %s" % (self.name, self.status, self.manager_name)
+class Company(object):
+    def __repr__(self):
+        return "Company %s" % self.name
+
+# assign plain vanilla mappers
+assign_mapper(Person, people)
+assign_mapper(Engineer, engineers, inherits=Person.mapper)
+assign_mapper(Manager, managers, inherits=Person.mapper)
+
+# create a union that represents both types of joins.  we have to use
+# nulls to pad out the disparate columns.
+person_join = select(
+                [
+                    people, 
+                    managers.c.status, 
+                    managers.c.manager_name,
+                    null().label('engineer_name'),
+                    null().label('primary_language'),
+                    column("'manager'").label('type')
+                ], 
+                people.c.person_id==managers.c.person_id).union_all(
+            select(
+                [
+                    people, 
+                    engineers.c.status, 
+                    null().label('').label('manager_name'),
+                    engineers.c.engineer_name,
+                    engineers.c.primary_language, 
+                    column("'engineer'").label('type')
+                ],
+            people.c.person_id==engineers.c.person_id)).alias('pjoin')
+            
+    
+# MapperExtension object.
+class PersonLoader(MapperExtension):
+    def create_instance(self, mapper, row, imap, class_):
+        if row[person_join.c.type] =='engineer':
+            return Engineer()
+        elif row[person_join.c.type] =='manager':
+            return Manager()
+        else:
+            return Person()
+            
+    def populate_instance(self, mapper, instance, row, identitykey, imap, isnew):
+        if row[person_join.c.type] =='engineer':
+            Engineer.mapper.populate_instance(instance, row, identitykey, imap, isnew)
+            return False
+        elif row[person_join.c.type] =='manager':
+            Manager.mapper.populate_instance(instance, row, identitykey, imap, isnew)
+            return False
+        else:
+            return True
+            
+        
+
+people_mapper = mapper(Person, person_join, extension=PersonLoader())
+
+assign_mapper(Company, companies, properties={
+    'employees': relation(people_mapper, lazy=False, private=True)
+})
+
+c = Company(name='company1')
+c.employees.append(Manager(name='pointy haired boss', status='AAB', manager_name='manager1'))
+c.employees.append(Engineer(name='dilbert', status='BBA', engineer_name='engineer1', primary_language='java'))
+c.employees.append(Engineer(name='wally', status='CGG', engineer_name='engineer2', primary_language='python'))
+c.employees.append(Manager(name='jsmith', status='ABA', manager_name='manager2'))
+objectstore.commit()
+
+objectstore.clear()
+
+c = Company.get(1)
+for e in c.employees:
+    print e, e._instance_key
+
+print "\n"
+
+dilbert = Engineer.mapper.get_by(name='dilbert')
+dilbert.engineer_name = 'hes dibert!'
+objectstore.commit()
+
+objectstore.clear()
+c = Company.get(1)
+for e in c.employees:
+    print e, e._instance_key
+
+objectstore.delete(c)
+objectstore.commit()
+
+
+managers.drop()
+engineers.drop()
+people.drop()
+companies.drop()