diff options
Diffstat (limited to 'examples/large_collection/large_collection.py')
| -rw-r--r-- | examples/large_collection/large_collection.py | 112 |
1 files changed, 68 insertions, 44 deletions
diff --git a/examples/large_collection/large_collection.py b/examples/large_collection/large_collection.py index 82d2e554b..eb014c6cb 100644 --- a/examples/large_collection/large_collection.py +++ b/examples/large_collection/large_collection.py @@ -1,54 +1,76 @@ - -from sqlalchemy import (MetaData, Table, Column, Integer, String, ForeignKey, - create_engine) -from sqlalchemy.orm import (mapper, relationship, sessionmaker) +from sqlalchemy import ( + MetaData, + Table, + Column, + Integer, + String, + ForeignKey, + create_engine, +) +from sqlalchemy.orm import mapper, relationship, 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') +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' : relationship(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( + Organization, + org_table, + properties={ + "members": relationship( + 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("postgresql://scott:tiger@localhost/test", echo=True) +if __name__ == "__main__": + engine = create_engine( + "postgresql://scott:tiger@localhost/test", echo=True + ) meta.create_all(engine) # expire_on_commit=False means the session contents @@ -56,10 +78,10 @@ if __name__ == '__main__': 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')) + 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) @@ -69,14 +91,14 @@ if __name__ == '__main__': # 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() + 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')) + 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() @@ -85,7 +107,9 @@ if __name__ == '__main__': # 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") + print( + "-------------------------\nflush three - delete org, delete members in one statement\n" + ) sess.commit() print("-------------------------\nno Member rows should remain:\n") @@ -93,4 +117,4 @@ if __name__ == '__main__': sess.close() print("------------------------\ndone. dropping tables.") - meta.drop_all(engine)
\ No newline at end of file + meta.drop_all(engine) |