updated the large_collection example to modern SQLA.

2 files changed, 100 insertions, 0 deletions

diff --git a/examples/large_collection/__init__.py b/examples/large_collection/__init__.py
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/examples/large_collection/__init__.py
diff --git a/examples/large_collection/large_collection.py b/examples/large_collection/large_collection.py
new file mode 100644
index 000000000..4d98eed2b
--- /dev/null
+++ b/examples/large_collection/large_collection.py
@@ -0,0 +1,100 @@
+"""Large collection example.
+
+Illustrates the options to use on relation() when the list of related objects
+is very large.
+
+"""
+
+from sqlalchemy import (MetaData, Table, Column, Integer, String, ForeignKey,
+                        create_engine)
+from sqlalchemy.orm import (mapper, relation, sessionmaker)
+
+
+meta = MetaData()
+
+org_table = Table('organizations', meta, 
+    Column('org_id', Integer, primary_key=True),
+    Column('org_name', String(50), nullable=False, key='name'),
+    mysql_engine='InnoDB')
+    
+member_table = Table('members', meta,
+    Column('member_id', Integer, primary_key=True),
+    Column('member_name', String(50), nullable=False, key='name'),
+    Column('org_id', Integer, ForeignKey('organizations.org_id', ondelete="CASCADE")),
+    mysql_engine='InnoDB')
+    
+    
+class Organization(object):
+    def __init__(self, name):
+        self.name = name
+    
+class Member(object):
+    def __init__(self, name):
+        self.name = name
+
+mapper(Organization, org_table, properties = {
+    'members' : relation(Member, 
+        # Organization.members will be a Query object - no loading
+        # of the entire collection occurs unless requested
+        lazy="dynamic", 
+        
+        # Member objects "belong" to their parent, are deleted when 
+        # removed from the collection
+        cascade="all, delete-orphan",
+        
+        # "delete, delete-orphan" cascade does not load in objects on delete,
+        # allows ON DELETE CASCADE to handle it.
+        # this only works with a database that supports ON DELETE CASCADE - 
+        # *not* sqlite or MySQL with MyISAM
+        passive_deletes=True, 
+    )
+})
+
+mapper(Member, member_table)
+
+if __name__ == '__main__':
+    engine = create_engine("mysql://scott:tiger@localhost/test", echo=True)
+    meta.create_all(engine)
+    
+    # expire_on_commit=False means the session contents
+    # will not get invalidated after commit.
+    sess = sessionmaker(engine, expire_on_commit=False)()
+
+    # create org with some members
+    org = Organization('org one')
+    org.members.append(Member('member one'))
+    org.members.append(Member('member two'))
+    org.members.append(Member('member three'))
+
+    sess.add(org)
+
+    print "-------------------------\nflush one - save org + 3 members\n"
+    sess.commit()
+
+    # the 'members' collection is a Query.  it issues 
+    # SQL as needed to load subsets of the collection.
+    print "-------------------------\nload subset of members\n"
+    members = org.members.filter(member_table.c.name.like('%member t%')).all()
+    print members
+
+    # new Members can be appended without any
+    # SQL being emitted to load the full collection
+    org.members.append(Member('member four'))
+    org.members.append(Member('member five'))
+    org.members.append(Member('member six'))
+
+    print "-------------------------\nflush two - save 3 more members\n"
+    sess.commit()
+
+    # delete the object.   Using ON DELETE CASCADE 
+    # SQL is only emitted for the head row - the Member rows 
+    # disappear automatically without the need for additional SQL.
+    sess.delete(org)
+    print "-------------------------\nflush three - delete org, delete members in one statement\n"
+    sess.commit()
+    
+    print "-------------------------\nno Member rows should remain:\n"
+    print sess.query(Member).count()
+    
+    print "------------------------\ndone.  dropping tables."
+    meta.drop_all(engine)
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